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Fairfield CBD Floodplain Risk Management Study and Plan Reference: R.S20152.001.03.docx Date: February 2018

Draft Report

A part of BMT in Energy and Environment

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Fairfield CBD Floodplain Risk Management Study and Plan

Prepared for: Fairfield City Council

Prepared by: BMT WBM Pty Ltd (Member of the BMT group of companies)

Offices Brisbane Denver London Mackay Melbourne Newcastle Perth Sydney Vancouver


Document Control Sheet

BMT WBM Pty Ltd 126 Belford Street Broadmeadow NSW 2292 Australia PO Box 266 Broadmeadow NSW 2292 Tel: +61 2 4940 8882 Fax: +61 2 4940 8887 ABN 54 010 830 421 www.bmtwbm.com.au

Document: R.S20152.001.02.docx

Title: Fairfield CBD Floodplain Risk Management Study and Plan

Project Manager: Darren Lyons

Author: Jessie Hayne, Paul Donaldson, Darren Lyons

Client: Fairfield City Council

Client Contact: Erensa Shrestha

Client Reference: VP-227752

Synopsis: This report documents the Fairfield CBD Floodplain Risk Management Study, which investigates and presents a flood risk management strategy for the overland flow catchment. The study identifies the existing flooding characteristics and canvasses various measures to mitigate the effects of flooding. The end product is the Floodplain Management Plan, which describes how flood liable lands within Fairfield CBD catchment are to be managed in the future.

REVISION/CHECKING HISTORY

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Fairfield City Council BMT WBM File BMT WBM Library

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Fairfield CBD Floodplain Risk Management Study and Plan i Executive Summary


Executive Summary Introduction

The Fairfield CBD catchment is located within the eastern portion of the Fairfield LGA and encompasses an area of approximately 2.9 km2 (refer to Figure 1-1). The overland flow catchment is situated on a low-lying floodplain near to Georges River. A flood study for the Fairfield CBD catchment was completed by Sinclair Knight Merz (SKM) on behalf of Fairfield City Council (Council) in 2010.

The primary objective of the flood study was to define the flood behaviour in the Fairfield CBD catchment through the establishment of appropriate numerical models. As part of the Floodplain Risk Management Study, BMT WBM reviewed and updated the SKM overland flood models in 2016 to reflect the existing catchment and floodplain characteristics and better define the associated overland flooding behaviour. This model review refined information on flood flows, velocities, levels and extents for a range of flood event magnitudes under existing conditions (refer to Figure 2-2).

The outcomes of the Flood Model Review (BMT WBM, 2016) establish the basis for subsequent floodplain management activities in the catchment to address local flooding issues. The Floodplain Risk Management Study (FRMS) aims to derive an appropriate mix of management measures and strategies to effectively manage flood risk in accordance with the NSW Government Floodplain Development Manual. The findings of the study will be incorporated in a Plan of recommended works and measures and program for implementation.

The objectives of the Fairfield CBD Floodplain Risk Management Study and Plan are to:

Identify and assess measures for the mitigation of existing flood risk;

Identify and assess planning and development controls to reduce future flood risks;

Identify and assess measures to address the residual flood risk for rare flooding; and

Present a recommended floodplain management plan that outlines the best possible measures to reduce flood risk in the Fairfield CBD catchment.

This report documents the Floodplain Risk Management Study and presents a recommended Floodplain Risk Management Plan for the Fairfield CBD catchment.

The following provides an overview of the key findings and outcomes of the study, incorporating a review of design flood conditions within the catchment, assessment of potential floodplain management measures and a recommended Floodplain Management Plan.

This project has been conducted by Fairfield City Council with financial and technical support from the Office of Environment and Heritage who administer the NSW Floodplain Management Program.

Flooding Behaviour

The Fairfield CBD catchment encompasses an area of approximately 2.9 km2, of which the majority is highly urbanised and comprised of residential land (~70%) and business zoned areas (>15%).

Fairfield CBD Floodplain Risk Management Study and Plan ii Executive Summary


The overland catchment flows in a general southeast direction through the residential area, to the CBD and beneath the railway line, before flowing through more residential areas and discharging to Orphan School Creek via St Elmos Drain. The railway embankment located downstream from the CBD forms a major constraint on surface drainage within the catchment, causing backwater influence to occur.

Urban stormwater is collected and conveyed by a network of surface pits and underground pipelines, which generally discharge to a creek, river or other waterway. Periods of large and/or intense rainfall can sometimes overload the pipe and channel system causing surface overflows (overland flows) and potential flooding.

Overland flows are typical in urban environments where it is not feasible to design stormwater drainage to capture very large and infrequent flood events. Often the overland flow paths are aligned with roads, however, in some instances, houses and other property may be located on or adjacent to major to overland flow routes. Overland flooding can be considered separate to mainstream flooding, such as that associated with major watercourses such as the Georges River, Prospect Creek and Orphan School Creek. Some property may experience flooding from both sources, either separately or combined. The current Fairfield CBD Floodplain Risk Management Study only addresses the local overland flooding component. Council has previously investigated mainstream flooding issues with the completion of the Prospect Creek Floodplain Management Plan Review (Bewsher, 2010).

It is typically short duration high intensity rainfall providing for the critical flood condition in the Fairfield CBD overland flow catchments given the highly urbanised environment. This typically would provide for a “flash flood” environment with limited opportunity for flood warning or coordinated flood response. The study has produced a number of mapping outputs to describe flood risk across the catchment for a range of flood magnitude events including peak flood inundation extent, depth, velocity and hazard (refer Figure 4-6). These outputs assist Council in ongoing development control and provide the basis for ongoing floodplain management in the catchment.

The study has also considered the potential for increased flood risk associated with potential climate change influences such as increases in storm frequency and rainfall intensity. Some increases in peak flood levels are expected with higher rainfall conditions and are noted in the study; however, the scale and magnitude of potential changes warrant so specific planning actions at this stage.

A flood damages databases has been developed to identify potentially flood affected properties and to quantify the extent of damages in economic terms for existing flood conditions. In developing the damages database, a floor level survey of all existing properties identified within the 1% AEP extent was undertaken. Key results from the flood damages database indicate:

324 residential dwellings and 230 commercial buildings with potential for flooding above floor level in a PMF event;

4 residential dwellings and 15 commercial buildings with potential for flooding above floor level in a 1% AEP flood;

Fairfield CBD Floodplain Risk Management Study and Plan iii Executive Summary


The predicted flood damage costs for the 1% AEP flood is in the order of $0.4M, increasing to $23M for the probable maximum flood.

Community Consultation

Community consultation was undertaken aimed at informing the community about the development of the Floodplain Risk Management Study and its likely outcome as well as improving the community’s awareness and readiness for flooding. The consultation process provided an opportunity to collect information on the community’s flood experience, their concern on flooding issues and to collect feedback and ideas on potential floodplain management measures and other related issues. The key elements of the consultation program involved:

Consultation with the Fairfield City Council Floodplain Management Committee through meetings and presentations;

Distribution of information brochure and questionnaire to stakeholder groups;

Distribution of information brochure and community questionnaire;

Public exhibition of the Draft Floodplain Risk Management Study and Plan; and

Community information session during the public exhibition period to present and discuss the outcomes of the study and recommended floodplain risk management options.

Floodplain Management Options Considered

Measures which can be employed to mitigate flooding and reduce flood damages can be separated into three broad categories:

flood modification measures: modify the flood’s physical behaviour (depth, velocity) and includes flood mitigation dams, retarding basins, on-site detention, channel improvements, levees, floodways or catchment treatment.

property modification measures: modify property and land use including development controls. This is generally accomplished through such means as flood proofing (house raising or sealing entrances), planning and building regulations (zoning) or voluntary purchase.

response modification measures: modify the community’s response to flood hazard by informing flood-affected property owners about the nature of flooding so that they can make informed decisions. Examples of such measures include provision of flood warning and emergency services, improved information, awareness and education of the community and provision of flood insurance.

The Fairfield CBD Floodplain Risk Management Study considered and assessed a number of floodplain management measures, summarised below.

Stormwater Drainage / Infrastructure Upgrades – localised drainage/infrastructure upgrades were assessed at a number of locations (refer Figure 9-1) to improve local flooding conditions in affected areas. Typically these options included augmentation of the existing stormwater drainage network through provision of additional pit and pipe capacity and regrading of roads to improve overland flow conveyance. Locations where specific works were assessed are shown in Figure 9-1 and include:

Fairfield CBD Floodplain Risk Management Study and Plan iv Executive Summary


– Nelson Street/Ware Street intersection drainage

– Barbara Street/Hamilton Road intersection drainage

– Hamilton Road drainage between Eustace Street and Sackville Street

– Hamilton Road drainage between Sackville Street and Thomas Street

– Railway culvert and inlet upgrade at Barbara Street/Railway Parade

– Regrading overland flow path adjacent recycled water treatment works

– Bunding adjacent to the open stormwater channel at Hamilton Road

– Regrading overland flow path in Council easement between Lyndon and Wilga Street

– Regrading of table drains to railway culvert near Railway Parade / Austral Parade

– Detention basins at existing Council car parks on Barbara Street

Most of the structural options above had limited impact on reducing flood conditions and accordingly not considered viable. The potential upgrade of the drainage across the railway embankment at Barbara Street (refer Figure 9-9) has some minor flood reduction benefit and may be considered further recognising significant constraints with regards to construction in relation to the railway and economic viability with high construction cost and limited flood reduction benefit.

Voluntary purchase - The primary objective of voluntary purchase is to reduce risks to personal safety by purchasing and removing houses located in areas subject to excessive hazard. A voluntary purchase scheme is generally applicable only to areas where flood mitigation is impractical and the existing flood risk is unacceptable. No properties have been identified as suitable for voluntary purchase within the Fairfield CBD overland flow catchment.

Voluntary house raising - raising floor levels where practical to elevate habitable floor levels to required levels above the flood planning level. Only a limited number of properties were identified with potential for above for flood flooding at the 1% AEP flood level. Not all houses are suitable for raising. Houses of brick construction or slab on ground construction are generally not suitable for house raising due to expense and construction difficulty. Generally this technique is limited to structures constructed on piers. No formal voluntary house raising program is recommended as part of the Plan as all houses identified with above floor flooding at the 1% AEP level are of brick construction. However, as an alternative to a VHR scheme, Council may give consideration to establishing a subsidy scheme for flood proofing of properties affected at the 1% AEP level.

Flood Proofing – Flood proofing refers to the design and construction of buildings with appropriate materials (i.e. material able to withstand inundation, debris and buoyancy forces) so that damage to both the building and its contents is minimised should the building be inundated during a flood. Flood proofing can be undertaken for new buildings or be retrofitted to existing buildings. Generally these works would be undertaken on a property by property basis at no cost to Council. A public awareness campaign may help to inform the community of flood proofing measures, and could be supplemented with individual building inspections and

Fairfield CBD Floodplain Risk Management Study and Plan v Executive Summary


property owner interviews. A detailed list of individual property levels relative to predicted flood levels has been established. For those properties identified within the 1% AEP flood envelope, advice may be provided to individual landowners on available opportunities to reduce on-site flood damages.

Planning and development controls - Land use planning and development controls are key mechanisms by which Council can manage flood-affected areas within the Fairfield CBD catchment. This will ensure that new development is compatible with the flood risk, and allows for existing problems to be gradually reduced over time through sensible redevelopment. The various flood risk mapping outputs updated for the current study are recommended to be adopted by Council and used in the development assessment process. Flood risk mapping outputs for the 1% AEP design event associated with overland flooding including design flood conditions (peak water level, depth and velocity), Flood Planning Area, hydraulic category (floodway, flood storage and flood fringe definition) and flood hazard mapping have been updated for Council use.

Other recent floodplain risk management studies for overland flow catchments in Fairfield LGA (e.g. Canley Corridor) incorporated detailed review of existing Council policies and flood related development controls. Some similar recommendations are considered appropriate and supported in the context of the Fairfield CBD catchment including:

– Freeboard in overland flow areas – Council to investigate opportunity for reduced freeboard of 300m (standard 500mm application) recognising nature of flooding in urban overland catchments compared to mainstream flood environments.

– Shelter in Place opportunity – Council to maintain provisions for potential shelter in place for new development. This again recognises the urban overland flood environment with typical flash flood scenarios where in some circumstances sheltering in place represents a lower (and/or tolerable) risk than evacuation. Council would be expected to consult with the NSW SES on this matter.

– On-Site Detention Policy – continued application of OSD Policy as means of addressing potential flood risk increases as a result of future catchment development.

– Fence Modification – recognition of the potential impact of fencing in an overland flow environment and consideration of development controls. For existing properties, further investigation of potential voluntary fence modification along identified flow paths.

Councils existing development controls provide for a suitable framework for establishing development requirements to manage flood risk. But little guidance is provided how best to accommodate overland floodwaters or best practice in how to protect proposed development from overland flooding. Given the nature of potential flooding in the Fairfield CBD, redevelopment and intensification of development as proposed in the CBD area would benefit from the use of a CBD Best Practice Design Guide that will focus on the mitigation of flooding in the locality and protect development from the impact of flooding.

Flood Warning Improvements– The local overland catchments in the study area are typically small urban catchments where the response to flooding is rapid (often within an hour of heavy

Fairfield CBD Floodplain Risk Management Study and Plan vi Executive Summary


rainfall). This provides little opportunity to provide a warning of flooding based on rainfall that has already occurred; to disseminate that warning to the public; and for the public to take appropriate action to reduce their exposure to the flood threat. Given the limited opportunity to provide any effective flood warning time, development of formal flood warning scheme for overland flooding is considered to be of little value.

Improved flood awareness – Raising and maintaining flood awareness will provide the community with an appreciation of the flood problem and what can be expected during flood events. An ongoing flood awareness program should be pursued through collaboration of the SES, Council and the flood affected community (e.g. FloodSafe program specific for the study area). The focus of this program should encourage landowners to develop their own Flood Plan for appropriate emergency response in lieu of reliance on Emergency Services as noted above.

The Canley Corridor Floodplain Risk Management Plan included a recommendation for the development and implementation of a City-wide community education program. The Fairfield CBD catchment area would be one part of this broader LGA initiative. Flood education programs for the Fairfield community need to recognise the cultural and linguistic diversity of the local population and cater for these needs. The Fairfield CBD catchment in particular has one of largest cultural diversities in the LGA such that appropriate flood education outcomes are required for residents of Non English Speaking Background

Update Local Flood Plan / Flood Intelligence Data - the key improvement to emergency response considered in the current study is to incorporate the flood intelligence data borne out of the revised understanding of catchment flooding conditions. This data includes the updated flood modelling, property inundation and flood damages analysis. It is important that the SES Plan incorporates all relevant technical data and specific community vulnerabilities (including addresses of areas at highest risk) that have been determined through the Floodplain Risk Management process.

The Recommended Floodplain Management Plan and Implementation

A recommended floodplain management plan showing preferred floodplain management measures for the Fairfield CBD catchment is presented in Section 10 in the main body of the report. The key features of the plan are tabulated below with indicative costs, priorities and responsibilities for implementation.

Summary of Proposed Actions, Works and Initiatives

Responsibility Cost Priority

Barbara Street Culvert Inlet Upgrades and Fairlight Ave Easement Regrading

Feasibility / Concept design study of options to increase culvert system capacity discharging through railway embankment

Council, Transport for NSW

$50K (feasibility) $1.4M (design and construction)

Medium

Planning Controls Adoption of updated flood study results. Update and implement changes to LEP/DCP incorporating:

- Apply FPLs on the basis of updated flood

Council Staff Costs High

Fairfield CBD Floodplain Risk Management Study and Plan vii Executive Summary




mapping developed in the current study - Adoption of flood planning area based on the

1% AEP + freeboard requirement - Adoption of hydraulic category and flood risk

mapping Review of planning recommendations from Canley Corridor study Preparation of Fairfield CBD Best Practice Design Guide.

Council $20K Medium

Improved Public Awareness Consolidation of the updated flood study flood risk mapping, flood data and flood damages database into Council’s GIS system.


Review flood affectation notations and provide flood certificates


Undertake targeted community flood education, awareness and resilience program with specific outcomes for Non English speaking community

Council, SES Staff Costs Low

Emergency Management Update and implement as required the SES Local Flood Plan to include flood intelligence data from current study

SES Staff Costs High

Property Modification Works Investigate flood proofing subsidy alternative to VHR Council $30K Low

Investigate fence modification Council $10K Low Flood proofing of individual properties Council, Landowner $20K Medium

The steps in progressing the floodplain management process from this point forward are as follows:

1. Council allocates priorities to components of the Plan, based on available sources of funding and budgetary constraints;

2. Council negotiates other sources of funding as required such as through State funded flood mitigation programs; and

3. as funds become available, implementation of the Plan proceeds in accordance with established priorities.

The Plan should be regarded as a dynamic instrument requiring review and modification over time. The catalyst for change could include new flood events and experiences, legislative change, alterations in the availability of funding or changes to the area’s planning strategies. In any event, a thorough review every five years is warranted to ensure the ongoing relevance of the Plan.

Fairfield CBD Floodplain Risk Management Study and Plan viii Contents


Contents Executive Summary i Glossary xvi 1 Introduction 1

1.1 Study Location 1 1.2 The Need for Floodplain Management at Fairfield Central Business District 2 1.3 The Floodplain Management Process 2 1.4 Structure of Report 4

2 Background Information 5

2.1 Catchment Description 5 2.2 History of Flooding 7 2.3 Previous Studies 7

2.3.1 Overland Flooding 7 2.3.1.1 St Elmos Drain Study (Willing and Partners, 1986) 7 2.3.1.2 Fairfield City Overland Flood Study (SKM, 2004) 8 2.3.1.3 Canley Corridor Flood Studies (SKM, 2009; BMT WBM, 2013) 8 2.3.1.4 Fairfield CBD Overland Flood Study (SKM, 2010) 8 2.3.1.5 Fairfield CBD Flood Model Review and Update (BMT WBM, 2016) 9 2.3.2 Mainstream Flooding 9 2.3.2.1 Prospect Creek Flood Study Reviews (Cardno Willing, 2004; Bewsher

Consulting, 2006) 9 2.3.2.2 Flood Studies for Orphan School Creek, Green Valley Creek and Clear

Paddock Creek (SKM & FCS, 2008; WMA water 2011; SKM 2011) 11 2.3.2.3 Prospect Creek Floodplain Management Plan Review (Bewsher, 2010) 11 2.3.2.4 Three Tributaries Floodplain Risk Management Study and Plan (Molino

Stewart, 2015) 12

3 Community Consultation 14

3.1 The Community Consultation Process 14 3.2 The Floodplain Management Committee 14 3.3 Stakeholder Consultation 14 3.4 Community Questionnaires 15 3.5 Public Exhibition 19 3.6 Social Implications 19 3.7 Environmental Issues 20

4 Existing Flood Behaviour 22

Fairfield CBD Floodplain Risk Management Study and Plan ix Contents


4.1 Flood Behaviour 22 4.1.1 Fairfield CBD Overland Flooding 22

4.2 System Capacity Assessment 25 4.2.1 Critical Drainage Infrastructure 28

4.3 Flood Risk Mapping 28 4.3.1 Hydraulic Categorisation 28 4.3.2 Flood Hazard 31 4.3.2.1 Size of Flood 31 4.3.2.2 Depth and Velocity 31 4.3.2.3 Flood Readiness 32 4.3.2.4 Rate of Rise 33 4.3.2.5 Duration of Flooding 33 4.3.2.6 Flood Warning Times 33 4.3.2.7 Obstruction to Flow 34 4.3.2.8 Effective Flood Access 34 4.3.3 Adopted Flood Hazard Categories 34 4.3.4 Flood Risk Precincts 35

5 Climate Change Analysis 37

5.1 Sea Level Rise 37 5.2 Rainfall 37

6 Review of Flood Emergency Management 41

6.1 Fairfield Local Flood Plan 41 6.2 Flood Emergency Response Planning Classification of Communities 43

6.2.1 Classification of FERP Communities for Fairfield CBD 45 6.3 Flood Education 49

7 Property Inundation and Flood Damages Assessment 50

7.1 Property Data 50 7.1.1 Location 50 7.1.2 Ground and Floor Levels 50 7.1.3 Flood Level 51

7.2 Property Inundation 51 7.2.1 Public and Private Assets 52 7.2.2 High Risk Assets 54

7.3 Flood Damages Assessment 56 7.3.1 Types of Flood Damage 56 7.3.2 Residential Flood Damages 57

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7.3.3 Commercial Flood Damages 58 7.3.4 Infrastructure and Public Sector Damages 58 7.3.5 Intangible Damages 59

7.4 Damages Summary 59

8 Review of Existing Planning Provisions 61

8.1 Local Environment Plan 61 8.1.1 Land Use 63

8.2 Development Control Plan 64 8.2.1 Fairfield Citywide Development Control Plan 2013 64 8.2.1.1 Chapter 2 Development Application Process: Step 3 Prepare Statement of

Environmental Effect and other required plans or reports 64 8.2.1.2 Chapter 3 Environmental Management and Constraints: Flood Risk

Management 66 8.2.1.3 Chapter 11 Flood Risk Management 66 8.2.2 Fairfield City Centre Development Control Plan 2013 68 8.2.3 Section 149 Planning Certificates 69 8.2.4 Stormwater Drainage Policy 2017 69

9 Potential Options for Improving Flood Management 71

9.1 Flood Modification Measures 71 9.1.1 Overview of Options 72 9.1.2 FM01 – Nelson/Ware Street 81 9.1.3 FM02 -Barbara Street/Hamilton Road Intersection 83 9.1.4 FM03 – Barbara Street Railway Culvert 87 9.1.5 FM04 – Hamilton Road between Eustace Street & Sackville Street 90 9.1.6 FM05 – Hamilton Road between Sackville Street & Thomas Street 93 9.1.7 FM06 – Railway Parade 94 9.1.8 FM07 – St Elmos Drain 97 9.1.9 FM08 – Hale Place and Nelson Street 98 9.1.10 FM09 – Hamilton Road Drainage Channel 98 9.1.11 FM10 – Wilga Street near Fairlight Avenue 99 9.1.12 FM11 – The Crescent 99 9.1.13 FM12 – Court Road 100 9.1.14 FM13 – Barbara Street 100 9.1.15 FM14 – Easement Between Lyndon Street and Wilga Street 101 9.1.16 Combinations of Flood Modification Options 103

9.2 Property Modification Measures 106 9.2.1 PM01 - Planning and Development Controls 107 9.2.1.1 Flood Planning Levels 108

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9.2.1.2 Section 149 Planning Certificates 109 9.2.2 PM02 - Voluntary Purchase 109 9.2.3 PM03 - Voluntary House Raising 111 9.2.4 PM04 - Flood Proofing 112 9.2.5 PM05 - Future Development 112 9.2.6 PM06 – Fencing 116

9.3 Response Modification Measures 117 9.3.1 EM01 - Flood Warning 118 9.3.2 EM02 - Emergency Response 120 9.3.3 EM03 - Community Awareness 121

9.4 Mainstream Flood Management Measures 122 9.5 Analysis of Potential Management Options 123

9.5.1 Summary of Short Listed Options 131

10 Floodplain Risk Management Plan 132

10.1 Recommended Measures 132 10.1.1 Flood Modification Measures 132 10.1.1.1 FM03d - Barbara Street Culvert Inlet Upgrades and Fairlight Ave Easement

Regrading 132 10.1.2 Property Modification Measures 133 10.1.2.1 Planning and Development Controls 133 10.1.2.2 Investigation of Flood Proofing Subsidy Alternative to Voluntary House

Raising 133 10.1.2.3 Flood Proofing 134 10.1.2.4 Fairfield CBD Best Practice Design Guide 134 10.1.3 Response Modification Measures 135 10.1.3.1 Update Relevant Local Flood Plan 135 10.1.3.2 Community Education and Awareness Program 135

10.2 Funding and Implementation 136 10.3 Plan Review 136

11 References 139

Appendix A Flood Mapping A-1

Appendix B Stakeholder and Community Consultation Material B-1

Appendix C Flood Modification Options – Afflux Mapping C-1

Appendix D Flood Damages Inputs D-1

Fairfield CBD Floodplain Risk Management Study and Plan xii Contents


List of Figures Figure 1-1 Study Locality 3 Figure 2-1 Topography of the Fairfield CBD Overland Flow Catchment 6 Figure 2-2 Design Overland Flood Inundation Extents 10 Figure 2-3 Prospect Creek Design Mainstream Flood Extents (Bewsher Consulting,

2006) 13 Figure 3-1 Building Type Responses 16 Figure 3-2 Flood Experience Responses 16 Figure 3-3 Flood Assistance Responses 17 Figure 3-4 Flood Evacuation Preference Responses 17 Figure 3-5 Preferred Council Assistance Responses 18 Figure 4-1 Overland Flooding Water Level Reporting Locations 24 Figure 4-2 Modelled Drainage Network 26 Figure 4-3 Pipe Capacity Assessment 27 Figure 4-4 Hydraulic Categories for the 1% AEP Event 30 Figure 4-5 Hydraulic Hazard as a Function of Depth and Velocity 32 Figure 4-6 Fairfield Flood Hazard Classification – 1% AEP Event 36 Figure 5-1 Projected Changes in Rainfall (Dowdy et al, 2015) 38 Figure 5-2 1%AEP Design Event with Climate Change Analysis 40 Figure 6-1 1% AEP Flood Emergency Response Classification 47 Figure 6-2 PMF Flood Emergency Response Classification 48 Figure 7-1 Distribution of Surveyed Flood Levels within the Fairfield CBD catchment 51 Figure 7-2 Potential Flood Affected Properties within Overland 1% AEP and PMF Extent 55 Figure 7-3 Types of Flood Damage 56 Figure 8-1 Fairfield CBD Land Use Zones 65 Figure 8-2 Flood Risk Assessment Processes for DA’s (Citywide DCP 2013) 66 Figure 8-3 Development Control Matrix for Local Overland Flooding (Citywide DCP 2013) 67 Figure 8-4 Fairfield City Boundary to which the City Centre DCP 2013 applies 68 Figure 9-1 Summary Map of Potential Mitigation Options: Fairfield CBD Overland

Catchment 78 Figure 9-2 Potential Mitigation Options 1 to 6: Fairfield CBD Overland Catchment 79 Figure 9-3 Potential Mitigation Options 7 to 14: Fairfield CBD Overland Catchment 80 Figure 9-4 FM01a Modelling Details 81 Figure 9-5 FM01b Modelling Details 82 Figure 9-6 FM02a Modelling Details 83

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Figure 9-7 FM02b Modelling Details 84 Figure 9-8 FM02b Regrading Surface from North Side of Hamilton Road 85 Figure 9-9 Barbara Street Long Section Map 86 Figure 9-10 Barbara Street Long Section Profile showing Design Flood Heights and

Highlighting the Design Specific Flooding Controls 87 Figure 9-11 FM03a Culvert Hydrograph 88 Figure 9-12 FM03a Modelling Details 88 Figure 9-13 FM03b Culvert Inlet Hydrograph 89 Figure 9-14 FM03b Modelling Details 90 Figure 9-15 FM04 Modelling Details 91 Figure 9-16 FM04 Flood Hazard 92 Figure 9-17 FM05 Modelling Details 93 Figure 9-18 FM06 Modelling Details 94 Figure 9-19 FM06 Modelled Surface 95 Figure 9-20 FM06 Flood Hazard 96 Figure 9-21 FM07 Modelling Details 97 Figure 9-22 FM09 Modelling Details 99 Figure 9-23 FM13 Modelling Details 101 Figure 9-24 FM14 Modelled Surface 102 Figure 9-25 FM14 Modelling Details 102 Figure 9-26 FM03c Modelling Details 103 Figure 9-27 FM03d Modelling Details 104 Figure 9-28 FM03d Long Section Profile 105 Figure 9-29 Flood Planning Area 110 Figure 9-30 Lots for Consideration of Fence Modification 116 Figure 9-31 Example of Automatic Flood Warning Signs 120 Figure A-1 20% AEP Design Event Flood Conditions A-2 Figure A-2 5% AEP Design Event Flood Conditions A-3 Figure A-3 1% AEP Design Event Flood Conditions A-4 Figure A-4 PMF Event Flood Conditions A-5 Figure A-5 20% AEP Design Event Velocity-Depth Product A-6 Figure A-6 5% AEP Design Event Velocity-Depth Product A-7 Figure A-7 1% AEP Design Event Velocity-Depth Product A-8 Figure A-8 PMF Design Event Velocity-Depth Product A-9 Figure A-9 20% AEP Design Event Flood Hazard A-10

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Figure A-10 5% AEP Design Event Flood Hazard A-11 Figure A-11 1% AEP Design Event Flood Hazard A-12 Figure A-12 PMF Design Event Flood Hazard A-13 Figure A-13 1% AEP Design Event + 10% Increase Rainfall A-14 Figure A-14 1% AEP Design Event + 20% Increase Rainfall A-15 Figure A-15 1% AEP Design Event + 30% Increase Rainfall A-16 Figure A-16 Flood Risk Precincts A-17 Figure C-1 FM01a Nelson St/Ware St Drainage –Change in Peak Flood Level C-2 Figure C-2 FM01b Nelson St/Ware St Regrading – Change in Peak Flood Level C-3 Figure C-3 FM02a Barbara St/Hamilton Rd Drainage –Change in Peak Flood Level C-4 Figure C-4 FM02b Barbara St/Hamilton Rd Regrading –Change in Peak Flood Level C-5 Figure C-5 FM03a Barbara St Railway Culvert Upgrade –Change in Peak Flood Level C-6 Figure C-6 FM03b Barbara St Inlet Capacity Upgrade –Change in Peak Flood Level C-7 Figure C-7 FM04 Hamilton Rd Drainage (Eustace/Sackville) – Change in Peak Flood

Level C-8 Figure C-8 FM05 Hamilton Rd Drainage (Sackville/Thomas) – Change in Peak Flood

Level C-9 Figure C-9 FM06 Railway Parade Culvert Inlet – Change in Peak Flood Level C-10 Figure C-10 FM07 St Elmos Drain Surface Drainage – Change in Peak Flood Level C-11 Figure C-11 FM09 Channel Bunding Hamilton Rd – Change in Peak Flood Level C-12 Figure C-12 FM13 Detention Basins – Change in Peak Flood Level C-13 Figure C-13 FM14 Easement Regrading (Lyndon St/Wilga St) – Change in Peak Flood

Level C-14 Figure C-14 FM03c Barbara St Railway Culvert and Inlet Upgrade –Change in Peak Flood

Level C-15 Figure C-15 FM03d Barbara St Railway Culvert /Inlet /Easement –Change in Peak Flood

Level C-16 Figure C-16 FM01a Nelson St/Ware St Drainage –Change in Peak Flood Level C-17 Figure C-17 FM01b Nelson St/Ware St Regrading – Change in Peak Flood Level C-18 Figure C-18 FM04 Hamilton Rd Drainage (Eustace/Sackville) – Change in Peak Flood

Level C-19 Figure C-19 FM05 Hamilton Rd Drainage (Sackville/Thomas) – Change in Peak Flood

Level C-20 Figure C-20 FM06 Railway Parade Culvert Inlet – Change in Peak Flood Level C-21

Fairfield CBD Floodplain Risk Management Study and Plan xv Contents


List of Tables Table 1-1 Stages of Floodplain Management 4 Table 3-1 Fairfield CBD Stakeholder Groups Consulted for this Study 15 Table 3-2 Flood Mitigation Measures Favoured by the Respondents 18 Table 4-1 Modelled Peak Flood Levels (m AHD) for Design Flood Events 23 Table 4-2 Critical Infrastructure 28 Table 4-3 Hydraulic Categories 29 Table 4-4 Flood Hazard Classification Thresholds 31 Table 4-5 Flood Warning Time Categories 33 Table 7-1 Floor Level Statistics for Available Property Survey Information 51 Table 7-2 Number of Flood Affected Properties 52 Table 7-3 Public and Private Assets within the Fairfield CBD 1% AEP and/or PMF extent 53 Table 7-4 Residential Damage Curve Inputs 57 Table 7-5 Summary of Residential Flood Damages 59 Table 7-6 Summary of Commercial Flood Damages 60 Table 7-7 Summary of Total Tangible Flood Damages 60 Table 9-1 Potential Flood Modification Options 73 Table 9-2 Potential Property Modification Options 106 Table 9-3 Potential Response Modification Options 117 Table 9-4 Rapid Analysis Assessment Criteria 124 Table 9-5 Assessment of Management Options 125 Table 9-6 Structural Flood Modification Option Validation 128 Table 10-1 Summary of Recommended Plan Measures 137

Fairfield CBD Floodplain Risk Management Study and Plan xvi Contents


Glossary

annual exceedance probability (AEP)

The chance of a flood of a given size (or larger) occurring in any one year, usually expressed as a percentage. For example, if a peak flood discharge of 500 m3/s has an AEP of 5%, it means that there is a 5% chance (i.e. a 1 in 20 chance) of a peak discharge of 500 m3/s (or larger) occurring in any one year. (see also average recurrence interval (ARI)) Relationship between AEP and ARI is described by:

Australian Height Datum (AHD)

A common national surface level datum approximately corresponding to mean sea level.

attenuation Weakening in force or intensity

average annual damage (AAD) Depending on its size (or severity), each flood will cause a different amount of flood damage to a flood prone area. AAD is the average damage per year that would occur in a nominated development situation from flooding over a very long period of time.

average recurrence interval (ARI)

The long-term average number of years between the occurrence of a flood as big as (or larger than) the selected event. For example, floods with a discharge as great as (or greater than) the 20yr ARI design flood will occur on average once every 20 years. ARI is another way of expressing the likelihood of occurrence of a flood event. (see also annual exceedance probability)

catchment The catchment at a particular point is the area of land that drains to that point.

design flood A hypothetical flood representing a specific likelihood of occurrence (for example the 100yr ARI or 1% AEP flood).

development Existing or proposed works that may or may not impact upon flooding. Typical works are filling of land, and the construction of roads, floodways and buildings.

discharge The rate of flow of water measured in tems of vollume per unit time, for example, cubic metres per second (m3/s). Discharge is different from the speed or velocity of flow, which is a measure of how fast the water is moving for example, metres per second (m/s).

effective warning time The time available after receiving advise of an impending flood and before the floodwaters prevent appropriate flood response actions being undertaken. The effective warning time is typically used to move farm equipment, move stock, raise furniture, evacuate people and transport their possessions

Fairfield CBD Floodplain Risk Management Study and Plan xvii Contents


flood Relatively high river or creek flows, which overtop the natural or artificial banks, and inundate floodplains and/or coastal inundation resulting from super elevated sea levels and/or waves overtopping coastline defences.

flood behaviour The pattern / characteristics / nature of a flood.

flood fringe Land that may be affected by flooding but is not designated as floodway or flood storage.

flood hazard The potential risk to life and limb and potential damage to property resulting from flooding. The degree of flood hazard varies with circumstances across the full range of floods.

flood level The height or elevation of floodwaters relative to a datum (typically the Australian Height Datum). Also referred to as “stage”.

flood liable land see flood prone land

floodplain Land adjacent to a river or creek that is periodically inundated due to floods. The floodplain includes all land that is susceptible to inundation by the probable maximum flood (PMF) event.

floodplain management The co-ordinated management of activities that occur on the floodplain.

floodplain risk management plan

A document outlining a range of actions aimed at improving floodplain management. The plan is the principal means of managing the risks associated with the use of the floodplain. A floodplain risk management plan needs to be developed in accordance with the principles and guidelines contained in the NSW Floodplain Management Manual. The plan usually contains both written and diagrammatic information describing how particular areas of the floodplain are to be used and managed to achieve defined objectives.

Flood planning levels (FPL) Flood planning levels selected for planning purposes are derived from a combination of the adopted flood level plus freeboard, as determined in floodplain management studies and incorporated in floodplain risk management plans. Selection should be based on an understanding of the full range of flood behaviour and the associated flood risk. It should also take into account the social, economic and ecological consequences associated with floods of different severities. Different FPLs may be appropriate for different categories of landuse and for different flood plans. The concept of FPLs supersedes the “standard flood event”. As FPLs do not necessarily extend to the limits of flood prone land, floodplain risk management plans may apply to flood prone land beyond that defined by the FPLs.

flood prone land Land susceptible to inundation by the probable maximum flood (PMF) event. Under the merit policy, the flood prone definition should not be seen as necessarily precluding development. Floodplain Risk Management Plans should encompass all flood prone land (i.e. the entire floodplain).

Fairfield CBD Floodplain Risk Management Study and Plan xviii Contents


flood source The source of the floodwaters. In this study, Hunter River flooding is the primary source of floodwaters.

flood storage Floodplain area that is important for the temporary storage of floodwaters during a flood.

floodway A flow path (sometimes artificial) that carries significant volumes of floodwaters during a flood.

freeboard A factor of safety usually expressed as a height above the adopted flood level thus determing the flood planning level. Freeboard tends to compensate for factors such as wave action, localised hydraulic effects and uncertainties in the design flood levels.

geomorphology The study of the origin, characteristics and development of land forms.

gauging (tidal and flood) Measurement of flows and water levels during tides or flood events.

historical flood A flood that has actually occurred.

hydraulic The term given to the study of water flow in rivers, estuaries and coastal systems.

hydrodynamic Pertaining to the movement of water

hydrograph A graph showing how a river or creek’s discharge changes with time.

hydrographic survey Survey of the bed levels of a waterway.

hydrologic Pertaining to rainfall-runoff processes in catchments

hydrology The term given to the study of the rainfall-runoff process in catchments.

isohyet Equal rainfall contour

m/s (metres per second) Unit used to describe the velocity of floodwaters.

m3/s (cubic metres per second)

Also referred as cumecs. A unit of measurement of creek or river flows or discharges. It is the rate of flow of water measured in terms of volume per unit time.

morphological Pertaining to geomorphology

peak flood level, flow or velocity

The maximum flood level, flow or velocity that occurs during a flood event.

pluviometer A rainfall gauge capable of continously measuring rainfall intensity

probable maximum flood (PMF)

An extreme flood deemed to be the maximum flood likely to occur.

Fairfield CBD Floodplain Risk Management Study and Plan xix Contents


probability A statistical measure of the likely frequency or occurrence of flooding.

riparian The interface between land and waterway. Literally means “along the river margins”

runoff The amount of rainfall from a catchment that actually ends up as flowing water in the river or creek.

stage equivalent to water level (both measured with reference to a specified datum - see flood level.

stage hydrograph A graph of water level over time.

sub-critical Refers to flow in a channel that is relatively slow and deep

topography The shape of the surface features of land

velocity The speed at which the floodwaters are moving. A flood velocity predicted by a 2D computer flood model is quoted as the depth averaged velocity, i.e. the average velocity throughout the depth of the water column. A flood velocity predicted by a 1D or quasi-2D computer flood model is quoted as the depth and width averaged velocity, i.e. the average velocity across the whole river or creek section.

water level See flood level.

Fairfield CBD Floodplain Risk Management Study and Plan 1 Introduction


1 Introduction The Fairfield CBD Overland Flood Study was prepared for Fairfield City Council (Council) by Sinclair Knight Merz (SKM) in 2010. This study defined the flood behaviour of the Fairfield CBD catchment which is subject to overland flooding from stormwater which runs off the highly-urbanised catchment and drains to Orphan School Creek. The railway embankment situated near the catchment outlet forms a major impediment to stormwater flow. Mainstream flooding also occurs along Prospect Creek and Orphan School Creek which boarder the downstream limit to the CBD overland catchment.

A number of changes to the CBD catchment development footprints and drainage networks have been made since the 2010 Overland Flood Study was completed by SKM. In addition, advances have been made in numerical modelling methods and capabilities. BMT WBM reviewed and updated the SKM overland flood models in 2016 to reflect the existing catchment and floodplain characteristics and better define the associated overland flooding behaviour. This model review refined information on flood flows, velocities, levels and extents for a range of flood event magnitudes under existing conditions.

The outcomes of the Fairfield CBD Overland Flood Study (SKM, 2010) and Flood Model Review (BMT WBM, 2016) established the basis for subsequent floodplain management activities in Fairfield CBD, addressing overland flooding risks primarily, but also acknowledging the mainstream flooding issues. The Floodplain Risk Management Study (FRMS) aims to derive an appropriate mix of management measures and strategies to effectively manage flood risk in accordance with the Floodplain Development Manual. The findings of the study will be incorporated in a Plan of recommended works and measures and program for implementation.

The objectives of the Fairfield CBD Floodplain Risk Management Study and Plan are to:

identify and assess measures for the mitigation of existing flood risk

identify and assess planning and development controls to reduce future flood risks, and

present a recommended floodplain management plan that outlines the best possible measures to reduce flood damages in the Fairfield CBD locality, where technical feasible and financially viable.

This report documents the Floodplain Risk Management Study and presents a recommended Floodplain Risk Management Plan for Fairfield CBD.

This project has been conducted under the State Assisted Floodplain Management Program and received State financial support.

1.1 Study Location The Fairfield CBD catchment is located within the eastern portion of the Fairfield LGA and encompasses an area of approximately 2.9 km2. The overland flow catchment is situated on a low-lying floodplain near to Georges River in the greater Sydney region of New South Wales. The study area is highly urbanised and includes the Fairfield CBD in addition to the Cabramatta to Granville Railway line that traverses the catchment southeast of the city centre. Land use within the



catchment is predominantly zoned for residential and business purposes. Suburbs located within the catchment include Fairfield and Fairfield Heights and the main streets include Railway Parade, Hamilton Road, Barbara Street, Sackville Street, Nelson Street and Station Street (Figure 1-1).

1.2 The Need for Floodplain Management at Fairfield Central Business District Fairfield CBD has a highly-urbanised catchment and is exposed to flooding from overland flow processes. Overland flows typically occur in urban environments where it is not feasible to design stormwater drainage to capture very large and infrequent flood events. The existing flood risk in the Fairfield CBD catchment is a legacy of historical catchment development with subdivision patterns that did not take into account the natural drainage paths. Further to this, the existing stormwater drainage system has limited capacity. Ongoing pressures for further re-development and intensification of existing development is likely to exacerbate the load on the stormwater drainage and overland flow system. For these reasons, Council has resolved to develop this Floodplain Risk Management Study and Plan. This Study and Plan follows on from significant prior investment by Council into floodplain risk management across study area and LGA more broadly.

Floodplain risk management considers the consequences of flooding on the community and aims to develop appropriate management measures to minimise and mitigate the impact of flooding. It includes considering existing flood risk associated with current development, and future flood risk associated with future development and changes in land use.

Accordingly, it is necessary to undertake local floodplain management in a considered and systematic manner. This study comprises the initial stages of that systematic approach, as outlined in the Floodplain Development Manual (NSW Government, 2005). The approach will enable more informed planning decisions within the floodplain of Fairfield CBD catchment.

1.3 The Floodplain Management Process The State Government’s Flood Prone Land Policy is directed towards providing solutions to existing flooding problems in developed areas and ensuring that new development is compatible with the flood hazard and does not create additional flooding problems in other areas. Policy and practice are defined in the Government’s Floodplain Development Manual (2005).

Under the Policy the management of flood liable land remains the responsibility of Local Government. The State Government subsidises flood mitigation works to alleviate existing problems and can provide specialist technical advice to assist Councils in the discharge of their floodplain management responsibilities.

The Policy provides for technical and financial support by the State Government through the sequential stages outlined in Table 1-1.



Figure 1-1 Study Locality



The Fairfield Overland Flood Study (SKM, 2010) and subsequent flood model update (BMT WBM, 2016) defines the existing flood behaviour and establishes the basis for future floodplain management activities.

The Fairfield CBD Floodplain Risk Management Study and Plan (this document) constitutes the fourth and fifth stages of the management process. It has been prepared for Council to provide the basis for future management of flood liable land within the catchment.

Table 1-1 Stages of Floodplain Management

Stage Description

1 Formation of a Committee Established by Council and includes community group representatives and State agency specialists.

2 Data Collection Past data such as flood levels, rainfall records, land use, soil types etc.

3 Flood Study Determines the nature and extent of the flood problem.

4 Floodplain Risk Management Study

Evaluates management options for the floodplain in respect of both existing and proposed developments.

5 Floodplain Risk Management Plan

Involves formal adoption by Council of a plan of management for the floodplain.

6 Implementation of the Floodplain Risk Management Plan

Construction of flood mitigation works to protect existing development. Use of local environmental plans to ensure new development is compatible with the flood hazard.

1.4 Structure of Report This report documents the Study’s objectives, results and recommendations.

Section 1 introduces the study.

Section 2 provides background information including a catchment description, history of flooding and previous investigations.

Section 3 outlines the community consultation program undertaken.

Section 4 describes the flooding behaviour in the catchment including climate change analysis.

Section 5 provides a review of the flood emergency management procedures.

Section 6 provides a summary of the flood damages assessment including identification of property potentially affected by flooding.

Section 7 provides a review of relevant existing planning measures and controls.

Section 8 provides an overview of potential floodplain risk management measures.

Section 9 presents the recommended measures and an implementation plan.

Fairfield CBD Floodplain Risk Management Study and Plan 5 Background Information


2 Background Information

2.1 Catchment Description Fairfield is situated within the Greater Sydney Region of NSW approximately 23 km west of the Sydney CBD. The Fairfield catchment occupies a total catchment area of around 2.9 km2, extending from around The Boulevard in the west, Station Street in the north, Prospect Creek in the east and Orphan School Creek in the south.

The topography of the catchment is shown in Figure 2-1. From a high elevation of around 40 m AHD occurring along the western catchment boundary, the topography grades gently eastward towards the central overland floodplain area in and around the CBD. Two subtle gullies trending west to east occur on these gentle slopes. The middle catchment area is low lying and mostly flat, sloping very gently in a southerly direction toward the mainstream floodplain area adjacent to the confluence of Orphan School Creek and Prospect Creek.

The catchment is highly urbanised and experiences overland flooding from catchment runoff causing the stormwater network to exceed capacity, as well as mainstream flooding which is most widespread along the southeast fringes of the catchment. The railway embankment that cross cuts the catchment in a southwest to northeast orientation, immediately downslope of the CBD, forms a major impediment to stormwater flow. Under extreme flood conditions, backwater flooding from the railway constriction would impact residential and business areas in and around the Barbara Street area.

Residentially zoned land comprises nearly 70% of land use within the catchment, with business zoned areas accounting for over 15% of area. Other land uses include recreational zones, an environmental zone and special purposes zones. The most densely developed area occurs within the City Centre, where multi-story buildings including large shopping complexes are located. Areas adjacent the two major creeks have the least development and include reserves and environmentally zone land for most of the creek length, with the exception of residential area located adjacent the confluence of the Orphan School and Prospect Creeks.



Figure 2-1 Topography of the Fairfield CBD Overland Flow Catchment



2.2 History of Flooding There is little recorded history of overland flooding within Fairfield CBD catchment. It is understood that a flood event occurred in October 1985, where residents indicated that water ponding to a depth of around 0.3m was experienced at the intersection of Sackville Street and Hamilton Road. This was confirmed by a nearby debris line. This event was estimated as being a similar temporal distribution and magnitude to a 5% AEP 12-minute storm event (Willing and Partners, 1986 & SKM, 2010).

Mainstream flooding of the lower Prospect Creek is closely related to flooding of the Georges River, which has a long history of flooding. Recent major flooding has occurred in August 1986, April 1988, April 2015 and June 2016.

2.3 Previous Studies Fairfield CBD catchment is exposed to both overland flooding within the central and downstream extent of the study area, in addition to mainstream flooding along the margins of Orphan School Creek and Prospect Creek. A number of flood studies are relevant to the study area. The available overland flood studies are briefly reviewed below (see Section 2.3.1), followed by a review of relevant mainstream flood studies (see Section 2.3.2).

2.3.1 Overland Flooding

2.3.1.1 St Elmos Drain Study (Willing and Partners, 1986) Fairfield City Council commissioned a flood study of St Elmos Drain to investigate the option of covering the open drain between Harris St and Hamilton Rd, and the associated flood impact from that proposed works. Whilst undertaking this study a flash flood occurred on 23 October 1985 and a number of flood level measurements were made. The study scope was then extended to include an options study for the protection of existing flood prone land near North Street in the vicinity of Orphan School Creek.

The 1985 storm was reported to have a 6 minute intensity equivalent to a 5% AEP storm. The storm lasted 12 minutes in total, but the catchment response was around 40 minutes.

RAFTS rainfall and runoff modelling was undertaken to simulate that storm, and achieved good agreement with measured flood levels. Discharge estimates were provided for a range of locations for a number of synthetic storms. The modelling indicated the capacity of the drainage system is equivalent to a 5% to 2% AEP event.

A residential area near North Street was identified as subject to backwater inundation from Orphan School Creek, the Railway Parade culvert and the creek between North Street and the railway. Problem areas upstream of Railway Parade were also identified, including a carpark near Fairfield Bowl and near the Sackville Street/Hamilton Road intersection.

A range of drainage upgrade options were detailed and costed for downstream of the railway, and recommendations provided.



2.3.1.2 Fairfield City Overland Flood Study (SKM, 2004) Council commissioned SKM, in partnership with Fairfield Consulting Services to undertake a preliminary assessment of flooding risk from overland flow for the urbanised areas of Fairfield LGA. This study prioritised a number of urban sub-catchments for a more detailed investigation. Fairfield CBD subcatchment was rated the second highest priority. This ultimately led to the 2010 overland flood study, summarised below.

2.3.1.3 Canley Corridor Flood Studies (SKM, 2009; BMT WBM, 2013) The Canley Corridor Flood Study was initially completed by SKM in associated with Fairfield Consulting Services (FCC) in 2009. Canley Corridor overland catchment is located immediately south of Orphan School Creek and boarders with the Fairfield CBD overland catchment towards its downstream end.

Hydrological and hydraulic models were developed to assess stormwater runoff from the catchment as part of the 2009 study. Three different hydrological and stormwater models were developed using DRAINS (XP-RAFTS), with the preferred model adopted for use. A two-dimensional hydraulic TUFLOW model was developed. Boundary inflow conditions were sourced from the SKM (2008) Three Tributaries XP Rafts flood model, while the downstream boundary was sourced from the Prospect Creek Flood Study (Bewsher, 2006). This study characterised the overland flooding behaviour of the catchment and produced flood maps for the 1% AEP event and flood risk precinct maps.

Subsequent to this study, BMT WBM was engaged to undertake the Canley Corridor Flood Study Review and Update (2014) to ensure the model was fit for purpose for the Flood Plain Risk Management Study and Plan. Review of the SKM/FCC DRAINS and TUFLOW models identified issues with the original hydrological and hydraulic modelling.

BMT WBM implemented a number of changes to the model that ensured its suitability for undertaking assessment as part of the subsequent FPRMSP. Flood maps for the 20%, 5% and 1% AEP and PMF design event were reproduced, in addition to updating the flood hazard category and risk precent maps.

2.3.1.4 Fairfield CBD Overland Flood Study (SKM, 2010) Council commissioned SKM to define the flood behaviour in the Fairfield CBD overland catchment. For this task, a one-dimensional DRAINS hydrologic and hydraulic model of the stormwater network was established. In addition, a two-dimensional TUFLOW hydraulic model of the catchment was established that included a one-dimensional model of the stormwater network. Both models were dynamically linked. The model could not be calibrated due to the lack of historical data, but model outputs were compared to some known flood behaviour information which provided agreeable results.

The flood model was run for a range of event (5% AEP to PMF) and storm durations (30 minutes to 3 hours). Flood results were mapped for the 5%, 1%, 0.05% AEP and PMF design events. Flood results from the 1% AEP event indicate that floodwater typically flow through properties, with significant flowpaths impacting parts of Hamilton Road, Nelson Street, Wrentmore Street and



Barbara Street. Overland flooding in the CBD area is generally confined to the road corridors. Flood velocities within properties are generally less the 0.5m/s, but higher in some localities within the upper catchment.

Risk precinct maps were prepared based on the 1% AEP and PMF results. Areas of high risk occur in the open concrete channel section between Sackville Street and Hamilton Road, and the lower part of the catchment adjacent St Elmos Drain, in addition to other isolated pockets.

2.3.1.5 Fairfield CBD Flood Model Review and Update (BMT WBM, 2016) Council commissioned BMT WBM to review and update the Fairfield CBD flood models developed for the 2010 flood study (SKM, 2010). The 2010 flood model was updated by combining the Fairfield CBD and Bellinger Drain TUFLOW models using a rainfall-on-grid approach. This update was done to ensure that any cross-catchment flows within the Fairfield CBD would be properly accounted for, the latest digital elevation model and stormwater pipe network data was incorporated and the combined model would reflect Council’s current approach to overland flood modelling.

The TUFLOW model was used to derive a detailed representation of Fairfield CBD catchment for the 20%, 5%, 1% AEP and PMF events for numerous standard durations, with various boundary conditions. The 20% AEP, 5% AEP, 1% AEP and PMF extents are shown in Figure 2-2.

Comparisons between the 2010 and updated TUFLOW model found the design flood behaviour has changed.

2.3.2 Mainstream Flooding

2.3.2.1 Prospect Creek Flood Study Reviews (Cardno Willing, 2004; Bewsher Consulting, 2006) Fairfield City Council commissioned the Review of Prospect Creek Flood Levels (Cardno Willing, 2004), to provide Council with updated information about the existing flood behaviour and risks in the catchment. The study was based on a calibrated XP-RAFTS hydrology model and 2-dimensional TUFLOW hydraulic model. This was undertaken for the 5%, 2%, 1%, 0.05% AEP and PMF design events.

Prospect Creek Floodplain Management Plan – Flood Study Review (Bewsher Consulting, 2006) comprised a review of Cardno Willing’s (2004) Prospect Creek hydrology and hydraulic models. The review resulted in several changes to both models. The updated model extent included the lower Orphan School Creek catchment areas downstream of the railway line and therefore assessed all mainstream flooding issues related to the Fairfield CBD overland catchment area.



Figure 2-2 Design Overland Flood Inundation Extents



Changes were made to the RAFTS models to ensure consistency between models being prepared in other Fairfield City Council locations. Refinements to the TUFLOW hydraulic model were undertaken to provide a more detailed representation of flood behaviour in some locations. This model was also recalibrated to the 2001 flood and then used to generate flood conditions for the 5%, 2%, 1% AEP and PMF floods. The flood information provided by the updated models informed preparation of the Prospect Creek Floodplain Management Plan Review (Bewsher Consulting, 2010).

Under the 1% AEP design event, mainstream flooding was found to impact the following areas:

areas immediately adjacent to Prospect Creek upstream of the railway embankment, including parts of Alan Street and The Horsley Drive and adjacent properties

areas immediately adjacent to Prospect Creek between the railway line and Fairfield Park, and

widespread residential area immediately upstream of the Prospect and Orphan School Creek confluence, including the majority of residential allotments south of North Street.

Figure 2-3 presents the Prospect Creek flood study review design inundation extents in relation to the Fairfield CBD overland catchment.

2.3.2.2 Flood Studies for Orphan School Creek, Green Valley Creek and Clear Paddock Creek (SKM & FCS, 2008; WMA water 2011; SKM 2011) Flood modelling for the Three Tributaries floodplain has been undertaken in various stages. A Flood Study for Orphan School Creek, Clear Paddock Creek and Green Valley Creek (the “Three Tributaries” of Prospect Creek) was prepared by Sinclair Knight Merz and Fairfield Consulting Services in 2008 (SKM & FCS, 2008). The modelling was then reviewed and updated in stages by SKM and Fairfield Consulting Services and WMAwater. The final model and flooding behaviour defined by that model was used for development of a Floodplain Risk Management Study and Plan (see Section 2.3.2.2). The Three Tributaries catchment includes Orphan School Creek towards its upstream boundary with Railway Parade, some 2 km upstream of its junction with Prospect Creek. The flood study as associated models did not cover the length of Orphan School Creek located within the Fairfield CBD overland flow catchment.

2.3.2.3 Prospect Creek Floodplain Management Plan Review (Bewsher, 2010) Bewsher (2010) prepared a floodplain management study and plan for Prospect Creek. This study and plan reviewed and updated the preceding floodplain management studies prepared for Prospect Creek, including for Lower Prospect Creek (Willing and Partners, 1990) and for Upper Prospect Creek (Willing and Partners, 1993). The Plan Review involves investigation into measures to reduce the flood risk in the Prospect Creek catchment. This study and plan is based on a flood study review completed in 2004 by CardnoWilling (see Section 2.3.2.1).



A flood damages assessment details the number of homes inundated above floor level for design flood events up to the PMF condition. A total of 406 homes and 62 commercial and industrial buildings were estimated to be inundated above floor level in the 1% AEP flood. A number of regional roads were also identified as at risk from 1% AEP flooding. The average annual cost of flood damage was predicted at $40M. The total cost of damages if the 1% AEP flood was to occur was estimated at $52M.

Measures previously recommended for Prospect Creek were reviewed and new measures considered for the revised Plan. Management options included in the Plan include physical works, property modification measures, education and further studies, and flood response measures. Flood management actions targeted at areas adjacent the Lower Prospect Creek that sit within the Fairfield CBD overland catchment include:

flood risk management DCP provisions

flood warning measures

house raising

voluntary purchase, and

road raising.

2.3.2.4 Three Tributaries Floodplain Risk Management Study and Plan (Molino Stewart, 2015) A floodplain risk management study and plan was prepared for the Three Tributaries floodplain, which includes Orphans School Creek upstream of the Canley Value-Fairfield Railway, Clear Paddock Creek and Green Valley Creek. The overall catchment for the Three Tributaries floodplain overlaps with the Fairfield CBD overland catchment, however, the mainstream floodplain extent considered in the Three Tributaries management study does not consider the overland flow environment in the current Fairfield CBD study. Accordingly, the assessment of flood risks and management actions proposed within the Three Tributaries floodplain risk management study and plan have no direct relevance to the Fairfield CBD study and plan. Some broader catchment/LGA wide elements of the flood planning and emergency response measures however may inform the current study.



Figure 2-3 Prospect Creek Design Mainstream Flood Extents (Bewsher Consulting, 2006)

Fairfield CBD Floodplain Risk Management Study and Plan 14 Community Consultation


3 Community Consultation

3.1 The Community Consultation Process Community consultation has been an important component of the current study. The consultation has aimed to inform the community about the development of the floodplain risk management study and its likely outcome as a precursor to the development of the floodplain risk management plan. It has provided an opportunity to collect information on their flood experience, their concern on flooding issues and to collect feedback and ideas on potential floodplain management measures and other related issues. The key elements of the consultation process have been as follows:

consultation with the Floodplain Management Committee through meetings and presentations

distribution of information brochure and questionnaire to stakeholder groups

distribution of information brochure and community questionnaire, and

public exhibition of the Draft Floodplain Risk Management Study and Plan.

These elements are discussed in detail below.

3.2 The Floodplain Management Committee The study has been overseen by the FCC Floodplain Management Committee (Committee). The Committee has assisted and advised Council in the development of the Fairfield CBD Floodplain Risk Management Study and Plan.

The Committee is responsible for recommending the outcomes of the study for formal consideration by Council. Members of the Committee include representatives from:

Fairfield City Council

Office of Environment and Heritage (OEH)

Fairfield State Emergency Service

Local residents, and

Floodplain managers from neighbouring Councils.

3.3 Stakeholder Consultation An information letter and questionnaire was sent to a range of stakeholder groups within the catchment, including government agencies, utilities, businesses, community organisations and other interest groups. All agencies and organisations that were contacted are listed in Table 3-1.



Table 3-1 Fairfield CBD Stakeholder Groups Consulted for this Study

Category Agency / Organisation

Public Service

NSW Office of Environment and Heritage NSW Roads and Maritime Services NSW State Emergency Service Railcorp NSW Police Force – Fairfield Police Station NSW Department of Education and Communities Sydney Trains

Utility Jemena Energy Australia Sydney Water Corporation Ltd

Business Fairfield Chamber of Commerce NSW Business Chamber

Community

Fairfield Public School Our Lady of the Rosary Primary School Fairfield RSL Fairfield Nursery

The questionnaire asked stakeholders to provide information of flood history, identify any flooding issues and provide comment on future floodplain risk management.

Of the 16 stakeholders contacted, a total of two stakeholder responses were received by Council. From these responses, the key information included:

identification of frequent flash flooding on Railway Parade

recommendation to reduce localised flooding of properties through regular stormwater maintenance in the vicinity of Railway Parade, and

locations of infrastructure within and adjacent to the study catchment that have previously been and may be impacted by floodwaters.

A copy of the stakeholder questionnaire is provided in Appendix B.

3.4 Community Questionnaires In July 2017 a community questionnaire was distributed to landowners, residents and businesses located within the study catchment. Respondents were asked to provide information on previous flood history and their concerns or issues in regard to ongoing floodplain risk management in the catchment. A copy of the community newsletter and questionnaire is provided in Appendix B.

Across the study area Council received a total of 134 completed responses. Noting that some of the questions allowed multiple answers to be selected, a summary of the responses received from the community included:



87% of the respondents were from residential properties, with the remaining 13% from businesses (Figure 3-1). The majority of respondents owned the building they were in (79%), 14% rented and 7% leased.

Figure 3-1 Building Type Responses

Only 16% of respondents had previously experienced flooding at their property (Figure 3-2) and of these, only 4% had any records of flooding.

Figure 3-2 Flood Experience Responses

Most of the respondents (73%) identified that they have never seen or heard of any information about flooding in the local area. Additionally, 64% of respondents identified that they would not know how to protect themselves or their property if a flood was to occur. Almost all of the

87.0%

13.0%

Residential Business

16.0%

84.0%

Yes No



respondents (98%) have not prepared a written plan for their household or business to follow during a flood.

In the event of a flood, 63% of the respondents would contact the NSW State Emergency Service, 33% would contact emergency services (call ‘000’), 14% would contact Council and 23% were not sure who to contact.

Figure 3-3 Flood Assistance Responses

If a flood was to occur 46% of respondents would prefer to evacuate, 23% would prefer to stay in their house and 31% were unsure.

Figure 3-4 Flood Evacuation Preference Responses

When asked what kind of assistance they would like Council to provide to help them prepare for floods, the most common answer was a flood preparedness pack (46%), followed by online information (23%), not sure (23%) and a workshop (12%).

63.0%

33.0%

14.0%

23.0%

NSW SES Emergency Services ('000') Council Not Sure

46.0%

23.0%

31.0%

Evacuate Stay at Home Unsure



Figure 3-5 Preferred Council Assistance Responses

When asked who in the community should be responsible for reducing flood risks the majority of respondents indicated Council (86%) followed by NSW Government (54%), NSW State Emergency Services (30%) and landowners (16%).

82% of respondents think that Council should spend more on flooding controls and flood awareness in the area. Table 3-2 lists the flood mitigation measures favoured by the respondents with measures listed according to rank/popularity.

66% of respondents said they would consider voluntary fence modification if Council offered financial assistance. However, only 18% would consider it if Council was not to provide financial assistance.

Table 3-2 Flood Mitigation Measures Favoured by the Respondents

Flood Mitigation Measures Average Score Rank

Channel enhancement by removing flow restrictions in our creeks 8.4 1

Construction of new detention basins in open space / park areas 8.2 2

Preparation of a local flood plan which will be used by the local SES 8.2 2

Increasing capacity of existing detention basins 8.2 2

Development controls/constraints, especially floor-level controls, fencing controls and building material controls for new developments 8.1 3

Floodgates at the creek to stop flood water backing up in the drain when the creek floods 8.1 3

Creek restoration by removing concrete channels and replacing them with wider, natural creek lines 8 4

Flood levees or flow diversions to redirect water flow 8 4

Flow diversions in streets to redirect water flow along roads 8 4

46.0%

23.0%

23.0%

12.0%

Flood Preparedness Pack Online Information Not Sure Workshop



Flood Mitigation Measures Average Score Rank

Large scale redevelopment, planning developments with flooding and other water sensitive design elements 7.7 6

Flood education to show you how to prepare for and deal with floods 7.2 7

Flood proofing your home with water resistant materials 6.5 8

Voluntary house raising where council can provide financial assistance to raise your house above a certain flood level 6.3 9

On-site detention (i.e. holding water on your property) 5.4 10

Voluntary fence modification, having open style fences on your property 5.4 10

Non-voluntary fencing controls, restricting the type of fence you can use 5.2 11

Voluntary purchase where council can buy your property 5 12

3.5 Public Exhibition To be undertaken

3.6 Social Implications The community consultation responses provided a clear insight into the lack of existing community flood awareness within the Fairfield CBD study area. Almost two thirds of the respondents identified that they have not seen or heard any information about flooding in the area and furthermore, only approximately 35% of respondents would know how to protect themselves during a flood event. This lack of flood knowledge and awareness could in part be due to that fact that the majority of respondents have never experienced flooding at their property.

This general lack of flood awareness within the community also provides for relatively low levels of flood preparedness. The majority of respondents indicated not knowing what appropriate actions to take in the event of a flood. In addition, there was also obvious confusion over who should be contacted in a flood situation and the need to evacuate when flooding occurs.

In 2012, Fairfield City Council commissioned a survey of community flood awareness as part of the development of flood education and awareness plan (Molino Stewart 2012). Only a small section of the Fairfield CBD study area was targeted for the survey, however the results of the survey are considered indicative for the larger study area. The survey findings were generally consistent with the community consultation responses received during this study. The 2012 flood awareness survey revealed:

low levels of community flood awareness

lack of understanding of flood behaviour

very few residents had prepared a flood evacuation plan, and

a majority of residents knew to contact the SES.



The low flood risk awareness and preparedness of the community within the study area appears to be reflective of other catchments in Sydney that have not experienced major flooding in many years (similar to Fairfield).

These issues indicate that there is a clear need for a focused and targeted education program to increase community flood awareness, knowledge and flood preparedness within the Fairfield CBD study area. Community education and information dissemination related to flooding should be addressed as a management option of this study.

It is noted that in the 2016 Census1 over 20% of the population within the suburb of Fairfield identified that they speak a language other than English and do not speak English well or at all. Additionally, approximately 6.5% of the Fairfield community did not go to school and a further 11% did not complete more than the equivalent of Year 8 education. Any future flood education programs or information prepared need to consider the community demographic profile and associated barriers to effectiveness as education and language barriers affect a considerable cross section of the community.

In addition to private properties and individuals of the community being impacted by flooding, community based infrastructure is also at risk. Community networks are the formal and informal links between community members. Networks can range from something as simple as neighbour relations up to the more formal networks offered by business groups or sporting clubs. The major community networks or groups identified as active within the Fairfield CBD study area include the Fairfield Chamber of Commerce, schools, sporting clubs and social clubs such as the Fairfield RSL.

Based on the 1% AEP event mapping it is evident that the Fairfield Train Station, Fairfield RSL Club and the Fairfield City Leisure Centre will each be affected by flooding to varying extents. Minor flooding will occur in the areas surrounding these locations making access to these facilities more troublesome than under normal conditions. However, each of these services and club facilities are still accessible via Vine Street, with clear exit routes still accessible.

Although the Fairfield Train Station is accessible during the 1% AEP event, it appears that a section of the train tracks between Fairfield and Canley Vale Stations is inundated during this event. This may result in the train services ceasing which would affect and likely disadvantage not just the residents of the Fairfield CBD catchment that utilise this mode of public transport, but users of the entire line.

The Fairfield Forum Shopping Centre is also affected by flooding with areas off Court Road and Ware Street inundated under the 1% AEP event. This area houses a Coles supermarket. Access to the Forum is available via Station Street which will mean residents can still access the centre however residents may notice an increase in traffic in the area as all of the community will need to use this entrance/exit.

3.7 Environmental Issues The Fairfield CBD catchment is a largely urbanised area with only a small portion of vegetated space fringing the eastern catchment boundary. The majority of the vegetated area borders two

1 Refer to http://profile.id.com.au/fairfield/speaks-english?WebID=210

http://profile.id.com.au/fairfield/speaks-english?WebID=210



urban creeks – Prospect Creek in the north of the catchment and Orphan School Creek to the south of the catchment. Mapping of vegetation across Fairfield City prepared as part of the Fairfield Biodiversity Strategy - and subsequently updated by Council in 2015 - confirms that the only notable biodiversity and vegetation remaining in Fairfield CBD catchment is along the creek line on the western catchment boundary.

As it is a predominately urban catchment made up most of residential dwellings and commercial properties there are very few environmental drivers or issues of concern. However, the catchment drains into Orphan School Creek (via St Elmos Drain) and Prospect Creek waterways which then converge directly to the south-east of the catchment. Prospect Creek then continues to flow southward where it ultimately joins the Georges River.

Prospect Creek suffers from ‘urban stream syndrome’ characterised by an increased frequency and magnitude of erosive flows, poor water quality, changed channel morphology and replacement of native flora and fauna with species that are more tolerant of pollution and high frequent flows2. The urban creek syndrome is largely caused by catchment urbanisation and is strongly correlated with directly connected impervious area, which the Fairfield CBD has in abundance.

Although Prospect Creek already has poor water quality and environmental health it is important that it (and other tributaries) are not worsened by any future development or management actions undertaken by Council. The existing development controls administered by Fairfield City Council will assist in ensuring that any future development within the catchment does not impact on the downstream urban creeks and environment.

The recommendations made within this study will not have a significant impact on the general functioning and stream flow and flood regimes. As such, it is anticipated that the environmental impact of this management plan will be limited. However, in the event that any drainage system upgrades are recommended or implemented within the catchment, it is advised that downstream environmental considerations such as scour and erosion control works are also implemented.

2 Walsh C J, Roy A H, Feminella J W, Cottingham P D, Groffman P M & Morgan R P 2005, ‘The urban stream syndrome: current knowledge and the search for a cure’, Journal of the North American Benthological Society, 24(3): 706-723.

Fairfield CBD Floodplain Risk Management Study and Plan 22 Existing Flood Behaviour


4 Existing Flood Behaviour

4.1 Flood Behaviour The Fairfield CBD Overland Flood Study (SKM, 2010) that was subsequently reviewed and updated (BMT WBM, 2016), defined design flood levels within the Fairfield CBD for a range of design event magnitudes. The following sections provide a summary of the flooding behaviour experienced within the study catchment.

4.1.1 Fairfield CBD Overland Flooding The Fairfield CBD catchment encompasses an area of approximately 2.9 km2, of which the majority is highly urbanised and comprised of residential land (~70%) and business zoned areas (>15%). The overland catchment flows in a general southeast direction through the residential area, to the CBD and beneath the railway line, before flowing through more residential areas and discharging to Orphan School Creek via St Elmos Drain. The railway embankment located downstream from the CBD forms a major constraint on surface drainage within the catchment, causing backwater influence to occur.

The topography along the western catchment boundary is approximately 40 m AHD and grades gently eastward towards the central overland floodplain area in and around the CBD. Two subtle gullies trending west to east occur on these gentle slopes. The middle catchment area is low lying and mostly flat; sloping very gently in a southerly direction toward the mainstream floodplain area adjacent Orphan School Creek and Prospect Creek confluence.

Given the small size of the catchment and highly urbanised conditions, the Fairfield CBD catchment experiences flooding from high intensity short duration rainfall events in the order of 2 hours. Such events exceed the stormwater network resulting in overland flooding. Design event mapping for the 20%, 5%, 1% AEP and PMF events is presented in Appendix A.

During the 1% AEP event, a number of residential and business properties become inundated by floodwaters. Upstream of the railway embankment, two main flowpaths trend east along Nelson to Wrentmore Street and Hamilton Street, before converging toward the CBD along Barbara Street. Flooding depths are deepest immediately upstream of the railway embankment, which causes backwater inundation along and around Barbara Street to peak depths of 1.4 m.

Downstream of the CBD and railway, floodwaters flow towards St Elmos Drain past Fairlight Avenue, North Street, Taylor Street and Orchard Street, which impact a number of adjoining properties (see Figure A-3). Peak overland flow velocities are > 2.0 m/s within the open drains and 1.5 m/s along main flowpaths within road reserves, i.e. Hamilton Road. Depths are typically shallow (<0.5 m), but increase in areas upstream of the railway embankment that become inundated by backwaters (e.g. 0.5 to 1.0 m)

The inundation extents for the PMF event show an increased area at risk of flooding, especially at the following locations:

Railway Parade upstream of the Cabramatta-Granville railway line

Barbara Street between the railway culvert and Nelson Street



low-lying areas adjacent to St Elmos Drain

CBD areas adjacent to Prospect Creek and

flowpaths bound by Nelson Street and Wrentmore Street, and Hamilton Road and Kenyon Street.

During the PMF event, peak flood velocities are typically greater than 1.5 m/s in channels and > 2.0 m/s within the road reserves. Depths increase considerably from the 1% AEP event and are typically > 1.0 m. During the PMF event the railway overtops, reducing the backwater flooding upstream of the Barbara Street railway culvert but increasing flooding on the downstream side of the railway (see Figure A-4).

Simulated peak flood levels for design coincident flood events at selected locations shown in Figure 4-1 are summarised in Table 4-1.

Table 4-1 Modelled Peak Flood Levels (m AHD) for Design Flood Events

ID Location Flood Event Frequency

20% AEP 5% AEP 1% AEP PMF

1 The Boulevarde - 29.81 29.86 30.24 2 Eustace Street - 20.69 20.74 21.23 3 Richardson Street 19.21 19.28 19.33 19.77 4 Macquarie Street 21.49 21.55 21.60 21.96 5 Sackville Street (#1) 14.82 14.88 14.93 15.48 6 Sackville Street (#2) - 16.01 16.04 16.49 7 Hampton Street 12.65 12.72 12.77 13.16 8 Thomas Street 12.11 12.15 12.20 12.95 9 Railway Parade 9.24 9.32 9.39 10.39

10 Wrentmore Street 10.08 10.11 10.19 10.84 11 Barbara Street (#1) - 9.21 9.37 10.73 12 Barbara Street (#2) 9.06 9.07 9.26 10.68 13 Hamilton Road - - 9.15 10.54 14 Seven Ten Split 8.45 8.50 9.01 10.51 15 Fairlight Avenue (#1) - 7.80 7.93 8.75 16 Fairlight Avenue (#2) 7.22 7.45 7.55 8.61 17 St Elmos Drain U/S 6.74 6.85 6.92 7.44 18 St Elmos Drain D/S 2.67 5.62 5.62 4.95



Figure 4-1 Overland Flooding Water Level Reporting Locations



From Table 4-1 above it is evident that the main mechanism of flooding across the CBD is overland flooding that is shallow and where the flood risk does not increase significantly with increasing event magnitude, i.e. relative small increases in flood levels with increasing event magnitude. This is particularly evident at locations 1 to 13. Backwater flooding caused by the hydraulic control of the Cabramatta-Granville Railway increases flood levels more significantly with increasing event magnitude up to the PMF, shown at location 14. During the PMF event the railway overtops increasing levels on the downstream side of the railway. Mainstream flooding conditions in Prospect Creek are demonstrated at location 18 whereby flood levels are more constant during the higher magnitude events due to the filling and overtopping of the channel.

4.2 System Capacity Assessment The Fairfield City drainage network was modelled using a 2D domain of the catchment that was dynamically linked to a 1D domain containing the drainage structures of the catchment. The 1D network was used to simulate the drainage characteristics of the stormwater network to ensure a detailed representation of the network was included.

The modelled 1D network consists of 403 pits and 475 pipes within the study catchment as shown in Figure 4-2. As per the Flood Study Review, kerb inlet pit hydraulic characteristics were derived from the Hornsby Council pit database, Sutherland Council’s ‘grated sag’ pit characteristics were used for sag pits and the Department of Housing RM7 inlet pits were used for pits with bolted down lids. In addition to these characteristics, blockages for on-grade and sag pits were adopted using 30% for the 5% AEP event and 50% blockage for the 1% AEP and greater. In previous modelling additional inlet capacity was included at the most upstream reaches of each truncated drainage networks to account for losses in pit inlet capacity associated with inlet pits being removed from the model. As this version of the model contains pits and pipes upstream of these locations, the additional inlet capacity was removed.

To determine the sensitivity of structures within the drainage network, pits were modelled with and without blockages applied as shown in Figure 4-3. This figure demonstrates the pipes running at full capacity during the modelled events. Evidently, many of the pipes in the study catchment reach capacity at the 20% AEP event regardless of the blockage factor applied. Minor differences in the event at which pipes reached full capacity were mostly isolated to the upstream reaches of the pipe network around Sackville Street, Eustace Street and in the Fairfield CBD.



Figure 4-2 Modelled Drainage Network



Figure 4-3 Pipe Capacity Assessment



4.2.1 Critical Drainage Infrastructure Within the study catchment a number of critical infrastructure were identified based on their size, connections and impact on flooding conditions in the catchment across a number of events between the 20% AEP and 1% AEP event.

Table 4-2 Critical Infrastructure

Infrastructure ID General Location Event

L170z – 3.6 x 2.4 m (2) rectangular culvert

Cabramatta-Granville Railway at the southern end of Barbara Street

Reaches capacity at the 5% AEP event causing backwater flooding along Barbara Street

L170t – 4.5 x 1.8 m (1) rectangular culvert

Intersection of York Street and Barbara Street

Reaches capacity at the 20% AEP event causing flooding along Barbara Street

M200a – 1.2 m diameter circular culvert

Cabramatta-Granville Railway at the southern end of Barbara Street

Pipes upstream of the culvert reach capacity during the 20% AEP event causing localised flooding

L170ai – 4.5 x 1.5 m (2) rectangular culvert

Outlet to St Elmos Drain at North Street

Reaches capacity at the 20% AEP event

4.3 Flood Risk Mapping In parallel with this study, the existing TUFLOW model developed for the Flood Study was refined to represent changes in the catchment subsequent to completion of that study and apply advances in the modelling technology to synthesis overland flooding events (see Section 2.3.1.5 for brief review).

Design flood mapping for the 20% AEP, 5% AEP, 1% AEP and PMF events (derived from coincident flood conditions) has been reproduced utilising the updated model and is contained in Appendix A. Additional mapping has been undertaken as part of this floodplain risk management study to include hydraulic categorisation for all design events and to define the true flood hazard distributions.

4.3.1 Hydraulic Categorisation Hydraulic categorisation is used to identify flood behaviour and risk. Outcomes of the categorisation are primarily used to inform future land use planning. The categorisation is not used to assess individual developments, but rather to give a catchment-scale overview of which areas may be appropriate for various types of land use.

There are no prescriptive methods for determining what parts of the floodplain constitute floodways, flood storages and flood fringes. Descriptions of these terms within the Floodplain Development Manual (NSW Government, 2005) are essentially qualitative in nature. Of particular difficulty is the fact that the definition of flood behaviour and its associated impacts is likely to vary from one floodplain to another depending on the circumstances and nature of flooding within the catchment.

The hydraulic categories as defined in the Floodplain Development Manual are:



Floodway - Areas that convey a significant portion of the flow. These are areas that, even if partially blocked, would cause a significant increase in flood levels or a significant redistribution of flood flows, which may adversely affect other areas.

Flood Storage - Areas that are important in the temporary storage of the floodwater during the passage of the flood. If the area is substantially removed by levees or fill it will result in elevated water levels and/or elevated discharges. Flood Storage areas, if completely blocked would cause peak flood levels to increase by 0.1m and/or would cause the peak discharge to increase by more than 10%.

Flood Fringe - Remaining area of flood prone land, after Floodway and Flood Storage areas have been defined. Blockage or filling of this area will not have any significant effect on the flood pattern or flood levels.

A number of approaches were considered when attempting to define flood impact categories across the study catchment. The approach that was adopted derived a preliminary floodway extent from the velocity * depth product (sometimes referred to as unit discharge). The floodway extent was then locally adjusted where appropriate. The peak flood depth was used to define flood storage areas. The adopted hydraulic categorisation is defined in Table 4-3.

Table 4-3 Hydraulic Categories

Floodway Velocity * Depth > 0.1 Areas and flowpaths where a significant proportion of floodwaters are conveyed (including all bank-to-bank creek sections).

Flood Storage Velocity * Depth < 0.1 and Depth > 0.3 metres

Areas where floodwaters accumulate before being conveyed downstream. These areas are important for detention and attenuation of flood peaks.

Flood Fringe Flood extent of the design event

Areas that are low-velocity backwaters within the floodplain. Filling of these areas generally has little consequence to overall flood behaviour.

As shown in Figure 4-4, floodways are mostly confined to the main flowpaths along Hamilton Road and Barbara Street, and the channels within the catchment including St Elmos Drain and Prospect Creek. These are areas that convey the most flow through the catchment. The main flood storage areas are located adjacent to St Elmos Drain and within the Barbara Street backwater flooding area between the Barbara Street railway culvert and Harris Street.



Figure 4-4 Hydraulic Categories for the 1% AEP Event



4.3.2 Flood Hazard The Best Practice Flood Risk Management approach to flood hazard mapping (D. McLuckie et. al., 2014) classifies the floodplain into six distinct hazard zones (H1 to H6) based on important thresholds of flood depth, velocity and depth-velocity product. The adopted thresholds identify when modelled flood conditions would present a risk to people, vehicles and building construction types. A description of each hazard threshold is provided in Table 4-4.

The key factors influencing flood hazard or risk are:

size of the flood

flood depth and velocity

flood readiness

rate of rise - effective warning time

duration of inundation

obstructions to flow, and

access and evacuation.

Table 4-4 Flood Hazard Classification Thresholds

Hazard Classification

Description

H1 Relatively benign flow conditions. No vulnerability constraints.

H2 Unsafe for small vehicles.

H3 Unsafe for all vehicles, children and the elderly.

H4 Unsafe for all people and vehicles.

H5 Unsafe for all people and vehicles. Buildings require engineering design and construction.

H6 Unconditionally dangerous. Not suitable for any type of development or evacuation access. All building types considered vulnerable to failure.

4.3.2.1 Size of Flood The size of flood will have an obvious and significant influence on the degree of flood risk. Relatively frequent or minor floods would typically be associated with a low flood hazard, whilst the major or rare flood events are likely to provide for high hazard flood conditions.

The design flood extent for a range of flood magnitudes is shown in Figure 2-2.

4.3.2.2 Depth and Velocity Depth and velocity hazards have been identified according to the provisional hydraulic hazard categories provided in D. McLuckie et. al., 2014. This has been further sub-categorised to show the predominant ‘type’ of hydraulic hazard (i.e. high velocity, depth, or combination) as shown in Figure 4-5 below.



Figure 4-5 Hydraulic Hazard as a Function of Depth and Velocity

4.3.2.3 Flood Readiness The term ‘flood readiness’ encompasses a broad range of factors, including familiarity with flooding in the catchment, awareness of evacuation procedures and preparation for a flood (e.g. development of flood plans). Flood readiness can refer to individuals, organisations, communities and businesses.

The relatively recent mainstream flood events of April 2015 and again in June 2016 provided for first-hand experience of major flooding along the Prospect Creek floodplain and an indication of the potential flood risk. Combined with a number of catchment flood events in decades past, many landowners affected by these events would have a reasonable level of flood awareness, particularly in relation to flood effects on their own property.

With respect to overland flooding within the Fairfield CBD catchment, there have not been any recent of historical flood events of significance. As such, many landowners will not have had first-hand experience of major overland flooding, particularly for locations upstream of the railway embankment.

The community questionnaire responses indicated a general low level of flood awareness with respect to overland flooding risks within the catchment.



4.3.2.4 Rate of Rise The rate of rise of floodwaters is typically a function of the catchments topographical characteristics such as size, shape and slope, and also influences such as soil types and land use. Flood levels rise faster in steep, constrained areas and urbanised catchments, whereas in broad flat floodplains the rate of rise is slower. A fast rate of rise adds an additional hazard by reducing the amount of time available to prepare and evacuate. Given the highly urbanised conditions of the Fairfield CBD catchment, the overland flooding response is rapid where flooding generally occurs due to short-duration events, i.e. 1 hour in duration. The highly urbanised catchment responds in such a way that significant local overland flows can be generated for intense rainfall over short periods.

4.3.2.5 Duration of Flooding The greater the duration of flood inundation the greater the potential impacts on damages and disruption to the community.

The duration of flooding is largely related to the size and duration of the rainfall event over the catchment. Given the highly responsive nature of flooding within the catchment, the period of inundation is expected to be in the order of a few to several hours.

4.3.2.6 Flood Warning Times The amount of warning available for an approaching flood can have a significant impact on the risk to life. Less warning time clearly represents a greater risk to the community as there is less opportunity to respond appropriately and implement risk-reduction measures. Minimal warning time also means that emergency services are unlikely to be able to provide any assistance or direction for affected communities.

To assess flood warning opportunity for Fairfield CBD, consideration has been given to the levels of warning times as defined in Table 4-5.

Table 4-5 Flood Warning Time Categories

No effective warning <1 hr No time for pro-active and systematic organisation of flood mitigation, evacuation, emergency response etc. Individuals would be self-directed in emergency response.

Minimal warning 1-6 hrs Limited assistance and direction likely from emergency services. Measures requiring minimal time for implementation may be appropriate for flood management.

Moderate warning 6-12 hrs Potential assistance and direction from emergency services, depending on time of day. Measures requiring moderate time, or less, for implementation may be appropriate for flood management.

Good warning 12+ hrs Significant assistance and direction from emergency services may be available, including assistance with evacuation. Most measures requiring some form of on-demand implementation would be appropriate for flood management.

As discussed in Section 4.3.2.4, the catchment is highly responsive to rainfall with the peak flood level reached in less than 1 hour after the onset of flood producing rainfall. The residents of



Fairfield CBD catchment would therefore have minimal warning time (less than 1 hour) of an approaching flood event.

4.3.2.7 Obstruction to Flow An important factor that can influence the depth of flooding, and rate of water movement through the catchment is the presence of obstructions to floodwaters. Obstructions can be engineered structures such as buildings, embankments and fences, or natural features including trees and shrubs.

The railway embankment that runs southwest to northeast through the middle of the catchment, immediately downstream of the CBD, forms a significant obstruction to flood flow. Modelling indicates that under extreme storm events, flood water movement becomes constricted once the stormwater networks reach capacity resulting in backwater flooding and increased flood heights on and around Barbara Street between the railway culvert and Harris Street. The railway embankment also causes a small area of backwater flooding around the eastern end of The Crescent. The increased depth of flooding in this area results in an increased flood hazard and greater degree of flood damage.

4.3.2.8 Effective Flood Access Access and evacuation difficulties arise from:

high depths and velocities of floodwaters over access routes

difficulties associated with wading (uneven ground, obstruction such as fences)

the distance to higher, flood free ground

the number of people and capacity of evacuation routes

the inability to communicate with evacuation and emergency services

the availability of suitable equipment (e.g. heavy vehicles, boats)

a low level of community awareness of evacuation procedures or requirements, and

a willingness of residents to remain at their property.

There are only a small number of areas within the Fairfield CBD catchment that would potentially require evacuation in a major flood event (up to 1% AEP flood). These areas include the eastern end of The Crescent and Barbara Street immediately upstream of the railway embankment. However, it is expected that most of the catchment would not be able to be evacuated due to the minimal warning time afforded during flash flooding. Considering the generally shallow flood depths and narrow flowpaths experienced across much of the catchment, flood access is not considered a major constraint within the catchment.

4.3.3 Adopted Flood Hazard Categories The flood hazard categories adopted for Fairfield CBD catchment are presented in Figure 4-6. The high flood hazard areas (H5 to H6) are mostly localised to the channels of Prospect and Orphan School Creeks and St Elmos Drain. Isolated areas of H3 and H4 hazard categories are located in



the backwater flooding along Barbara Street, the eastern end of The Crescent and the railway embankment along the western end of Railway Parade. Other areas of H3 and H4 hazards are mostly located within major flowpaths due to the depth and velocity of flooding. The majority of the catchment is classed as H1 and H2 hazards due to the shallow nature of overland flooding.

4.3.4 Flood Risk Precincts Flood risk, or hazard, is a measure of the overall potential adverse impact of flooding that considers threat to life, danger and difficulty in evacuating people and possessions, and the potential for damage, social disruption and loss of production. The degree of flood risk varies across a catchment.

The following categorisation has been adopted in the study to identify relative risk within the catchment and to guide planning controls appropriate for the different flood risk categories:

High Flood Risk – land below the 1% AEP flood level that is either located within floodway area, subject to a high hydraulic hazard (as defined in Figure L2 of the Floodplain Development Manual) or where there are significant evacuation difficulties.

Medium Flood Risk – Land below the 1% AEP flood level that is not subject to high hydraulic hazard and where there are no significant evacuation difficulties

Low Flood Risk – All land within the floodplain (i.e. within the PMF extent) but not identified as either in a high or medium flood risk area.

The high flood risk area is where high flood damages, potential risk to life, or evacuation problems are anticipated. Most development should be restricted in this area.

The medium flood risk area is where there is still significant risk of flood damage, but where these damages can be minimised by the application of appropriate development controls.

The low flood risk area is that area above the 1% AEP flood, where the risk of damage is low based on the likelihood of flooding alone. Most land uses would be permitted within this area.

The adopted flood risk precincts for the study area are shown in Figure A-16. High flood risk precincts are mostly localised to drains and channels, such as St Elmos Drain, Orphan School Creek and Prospect Creek.



Figure 4-6 Fairfield Flood Hazard Classification – 1% AEP Event

Fairfield CBD Floodplain Risk Management Study and Plan 37 Climate Change Analysis


5 Climate Change Analysis Climate change is recognised as an important factor for inclusion in long-term planning. Nationally, an average increase of 1oC in both surface air and sea surface temperature has been experienced over the last century. The CSIRO has predicted an increase in extreme rainfall events and other extreme climate events such as drought, winds, storms and fire across the Sydney region (CSIRO, 2016).

The NSW Floodplain Development Manual (DIPNR, 2005) requires climate change to be considered in the preparation of Floodplain Risk Management Studies and Plans, with further guidance provided in:

Floodplain Risk Management Guideline – Practical Consideration of Climate Change (DECC, 2007); and

Flood Risk Management Guide – Incorporating Sea Level Rise Benchmarks in Flood Risk Assessments (DECCW, 2010).

5.1 Sea Level Rise The NSW Sea Level Rise Policy Statement (DECCW, 2009) was prepared to support the consistent adaptation of projected sea level rise impacts, ensuring that sea level rise planning benchmarks were included for addressing coastal and flood-related sea level rise impacts. The benchmarks included projected increases in sea levels relative to the 1990 mean sea level of 0.4 m by 2050 and 0.9 m by 2100.

In 2012, the NSW Government announced it no longer recommended state-wide sea level rise benchmarks for use by local councils and accordingly provided councils with the flexibility to consider local conditions when assessing future hazards within their LGA. Despite this, these benchmarks remain the best available estimates in many LGAs.

FloodMit (2011) found that sea level rise along would have negligible impacts on flood behaviour and levels along Prospect Creek. Similarly, Molino Stewart (2015) inferred from this information that sea level rise would not impact flooding in Prospect Creek and excluded it from their study. As such, sea level rise impacts are not considered to impact on flood conditions within the study catchment and have been excluded from this study.

5.2 Rainfall Current research predicts that one of the likely outcomes of future climate change will be an increase in flood-producing rainfall intensities. This may include increased frequency, duration and height of flooding and consequently increased number of emergency evacuations and associated property and infrastructure damage.

The predicted impact of climate change on rainfall conditions includes:

Increase in average annual rainfall – changes in annual rainfall conditions is unlikely to have a significant on impact on flooding regimes. However, wetter than average conditions may increase the opportunity for wet antecedent conditions at the onset of a rainfall event.



Increases in rainfall intensity – climate change impacts on flood producing rainfall events are expected to show a trend for more frequent, higher intensity storms.

In 2007, the NSW Government released a guideline for the Practical Consideration of Climate Change in the floodplain management process that advocates consideration of increased design rainfall intensities of up to 30 percent (DECC, 2007). The State of the Climate report (CSIRO, 2016) notes that the frequency and intensity of rainfall is projected to increase across most of Australia, however the increases in rainfall will vary depending on the region.

Dowdy et al. (2015) includes projected changes in heavy rainfall events including the potential increase in 20-year return period maximum 1-day rainfall as shown in Figure 5-1. The blue and purple columns in Figure 5-1 represent the RCP4.5 and RCP8.5 scenarios respectively. The relative change in the 20-year return level of maximum 1-day rainfall is approximately 18% for the low-emissions pathway (RCP4.5) and 25% for the high-emissions pathway (RCP8.5).

Figure 5-1 Projected Changes in Rainfall (Dowdy et al, 2015) Therefore, due to the uncertainty associated with projected rainfall increases, an analysis of climate change related increases in rainfall and the impact on future flood conditions within the catchment has been undertaken on the 1% AEP event with 10%, 20% and 30% increases in rainfall. Modelling of these projected rainfall increases is in accordance with the Practical Consideration of Climate Change Floodplain Risk Management Guideline (DECCW, 2007).

The change in peak flood extents is shown in Figure 5-2. It is evident that there is little change to the 1% AEP flood extent across most of the catchment, with the greatest change in extent shown along the stretch of Barbara Street between the Cabramatta-Granville Railway and Harris Street.

Impacts on peak flood levels are included in Appendix A. Similar to the flood extents, the greatest impact on peak flood level is along Barbara Street upstream of the rail culvert during all of the modelled climate change scenarios. Peak flood levels along Barbara Street increased by 0.2, 0.4



and 0.5 m for the 10%, 20% and 30% increase in rainfall scenarios. The most upstream reaches were minimally impacted with peak flood level increases up to 0.09 m during the 1% AEP with 30% increased rainfall.



Figure 5-2 1%AEP Design Event with Climate Change Analysis

Fairfield CBD Floodplain Risk Management Study and Plan 41 Review of Flood Emergency Management


6 Review of Flood Emergency Management The following chapter provides a review of emergency management for overland flooding of Fairfield CBD.

The Fairfield Local Flood Plan, last updated in 2016 by the NSW SES, provides high-level guidance in relation to flood preparedness, response and recovery measures. A new valley Flood Emergency Sub Plan (Georges River Valley including the Woronora River the Georges and Woronora River Valley Flood Emergency Sub Plan) is currently in preparation by the NSW SES. This Valley Plan will replace the 7 Local Flood Plans (one of which being Fairfield) providing an overarching plan for riverine flooding on the Georges/Woronora River system. The Local Flood Emergency Sub Plans will be repealed as the information related to these areas are in the new River Valley Flood Plans.

6.1 Fairfield Local Flood Plan The Fairfield City Local Flood Plan 2016 (the Flood Plan) has been prepared by the NSW State Emergency Service (SES) and adopted by the Local Emergency Management Committee (LEMC). It forms a sub-plan of the Local Disaster Plan (DISPLAN), and covers preparedness measures, the conduct of response operations and the coordination of immediate recovery measures from flooding within Fairfield City Council

A summary of the information contained in the Flood Plan is outlined below:

Flood Preparedness – measures taken to prepare for flooding including:

○ maintenance of the Flood Plan

○ ensuring SES participation in floodplain management

○ development of flood intelligence (including undertaking flood studies and floodplain management studies and plans)

○ development and maintenance of flood warning systems

○ public education, and

○ SES training

Response – measures taken to respond to flood events, including:

○ operational management including defining clear roles or responsibility during flood events;

○ response operations

○ provision of flood information and warnings (including issues and dissemination of flood warnings);

○ road and traffic control

○ evacuation plans

Recovery – measures taken to recover from a flood event



Riverine flooding is largely the focus of the existing Plan and in the context of the current study area identifies existing flood risks within part of the Prospect Creek floodplain. Prospect Creek flood conditions are monitored through the existing flood warning gauge network. Existing residential and commercial property at risk from Prospect Creek mainstream flooding has been considered as part of the Prospect Creek Floodplain Management Plan Review (Bewsher, 2010). In addition, the Local Flood Plan identifies flood risk associated with:

Flooding of key road routes including The Horsley Drive and Railway Parade Fairfield

Special use properties prone to flooding including Patrician Brothers Fairfield, Fairfield High School and Fairfield Nursing Home.

Whilst not included in the 2016 Fairfield Local Flood Plan, the previous 2005 Fairfield Local Flood Plan listed potential evacuations centres including:

Police Citizens Youth Club, Railway Parade, Cabramatta

Fairfield RSL Club, Dale Street, Fairfield.

The Fairfield RSL Club is located within the CBD overland flow catchment, opposite and southeast of the railway station. This building is central to the flood affected areas and only marginally impacted by the design PMF flood event. The Police Citizens Youth Club is positioned 2 - 3 km south of the flood affected areas in and around Fairfield. No specific details are provided in relation to evacuation routes within the Fairfield CBD overland catchment.

The Canley Corridor Floodplain Risk Management Study (Molino Stewart, 2015) included an emergency management review for an overland flooding catchment similar to the Fairfield CBD study area. Acknowledging a similar “flash flood” environment as the Fairfield CBD study area, it was noted that with limited opportunity for flood warning there is very little time for the SES to provide complex response activities in the highly built up catchment. Coupled with potentially limited local resources, the SES role in the catchment would likely concentrate on the prevention, preparedness and recovery functions.

Molino Stewart (2015) further notes during consultation with the NSW SES acknowledged particular challenges with flooding in the Canley Corridor catchment including:

There are less than 50 volunteers and staff within the local unit servicing a population of more than 50,000 potentially affected by flooding within the whole of the Fairfield City LGA.

There are locations within the LGA where the flood hazards are significantly greater than those in Canley Corridor and these would need to be given priority.

It will be extremely difficult to call on neighbouring SES units as they are more than likely to be employed in similar flood emergencies in their areas and the short response time of the overland flooding means that would be insufficient time for responders from outside the LGA to arrive before the flooding had peaked.

The potential for high hazard floodwaters along the roads, particularly in the middle of the catchment, will make it dangerous for building occupants to leave or for SES personnel to try and reach them after a short time into the larger floods.



The above constraints for flood emergency response may be considered typical in an urban overland flooding context and applicable to the Fairfield CBD study area.

A key outcome of the emergency response review undertaken for the Canley Corridor Floodplain Risk Management Study was the acknowledgement that the shelter in place option is the most practical and safest response for building occupants during a flood. This recognised that for most locations in the catchment it is safer to stay within buildings rather than evacuate through more hazardous flood waters in the street. The ‘flashy’ nature of flooding suggests that it will always be difficult to ensure everyone in the floodplain evacuates prior to flooding of evacuation routes. Similar flood conditions are prevalent in the Fairfield CBD catchment. This also recognises the typically short duration and low hazard of floods in this area, which suggests that isolation is likely to be limited to about a few hours in most events. The study noted that as a way of reducing existing risks to life, shelter-in-place should at least be made available for the concessional development category. It is also defensible for existing residential areas where urban renewal is occurring.

Accordingly, the Floodplain Risk Management Plan recommendations incorporated:

Update of Local Flood Plan to acknowledge that evacuation is not a practical option for most buildings and provision for shelter in place is appropriate for new developments

Community education material to incorporate content on sheltering in place

Review DCP to ensure development controls continue permitting a shelter in place approach.

Given the similar nature of the flash flood environment of the Fairfield CBD, these recommendations around shelter in place are considered appropriate in the current study.

6.2 Flood Emergency Response Planning Classification of Communities The Office of Environment and Heritage (formerly Department of Environment and Climate Change), in conjunction with the State Emergency Service (SES) developed the Flood Emergency Response Planning Classification of Communities (2007) guideline. The guideline provides a process for classifying flood-affected communities according to their vulnerability during flood emergency response and by the impact that flooding has on them. This is undertaken to assist in future planning for catchments and for the implementation of response strategies by the SES. During flood events, the normal functioning of services within the community can be altered, impacting on evacuation, resupply and rescue of those affected. Flood-affected communities can be classed as:

flood islands (high or low)

trapped perimeter areas (high or low)

areas able to be evacuated (with overland escape routes or rising road access)

indirectly affected areas, and

overland refuge areas.



A description of each of the above is given below.

Flood Islands

Flood islands are areas of higher ground within a floodplain linked to flood-free valley sides by only one access route with no alternative overland access. This route can become inaccessible to cars by floodwater preventing vehicular or pedestrian evacuation and creating a ‘flood island’. These islands can be further classed according to what happens to the island following the evacuation route being cut and are generally categorised as high flood islands and low flood islands.

A high flood island includes sufficient land above PMF flood levels to provide refuge for the number of people in the area. During flood events, the area is surrounded by floodwater with potential property inundation and community isolation occurring. The higher ground above PMF flood levels allows people to retreat to safety, limiting the direct risk to life. Due to the surrounding floodwater, resupply is required via boat or air if the area is not evacuated prior to the access road being cut off.

A low flood island is an area where the land is below the limit of flood (the PMF level), or where there is insufficient land above the limit of flooding to accommodate for the number of people in the area. During flood events, properties are inundated and the community becomes isolated. If floodwater continues to rise after the area becomes cut off, the island will be completely inundated by floodwater leaving stranded people prone to drowning.

Trapped Perimeter Areas

Trapped perimeter areas are generally inhabitable or potentially habitable areas at flood fringe regions of the floodplain where the only practical overland access is through flood prone land which may be inaccessible during flood events. Trapped perimeter areas do not allow for people to retreat to higher ground as the topography may be too low or impassable structures may block access routes. Trapped perimeter areas are further classified as high trapped perimeter areas or low trapped perimeter areas according to what happens after the evacuation route is cut off.

A high trapped perimeter area includes sufficient land located above the limit of flooding (such as the PMF event) to accommodate for the number of people in the area. During a flood event, the area may become isolated by floodwater and property may be inundated. However, there may be higher ground above the PMF level available for people to retreat to, limiting the direct risk to life. The trapped area would require resupply by boat or air if not evacuated prior to the access road being cut off.

A low trapped perimeter area is located below the limit of flooding, or may not provide sufficient land above the limit of flooding to accommodate for the number of people in the area. During a flood event the area is isolated by floodwater and properties may become inundated. If floodwater continues to rise after the area becomes isolated, the area will be completely covered. Stranded people are susceptible to drowning.

Areas Able to be Evacuated

These areas are located on flood prone fringes in the floodplain, or on the valley sides in areas able to be evacuated. Areas able to be evacuated are further classed as areas with overland escape routes or as areas with rising road access depending on the type of evacuation access



available. These communities contain low-lying areas from which people will be progressively evacuated to higher ground as the level of inundation increases.

Areas with overland escape routes are those where access roads to flood free land cross lower lying flood prone areas. As such, evacuation can only take place by road until the access roads are closed by floodwater. Escape from rising floodwater is possible via walking to higher ground with those unable to do so evacuated via boat or air. If inundation occurs prior to evacuation, rescue will likely be from rooftops.

Areas with rising road access are those where access roads to flood free land rise steadily uphill away from rising floodwaters. As such, the community cannot be completely isolated before inundation reaches it maximum extent, even during the PMF event. Evacuation can occur by vehicle or on foot as floodwater rises and people should not be trapped unless evacuation is delayed.

Indirectly Affected Areas

Indirectly affected areas are located outside the limit of flooding and are consequently not inundated, nor do they lose road access. These areas may be indirectly affected as a result of flood-damaged infrastructure or due to the loss of transport links, electricity supply, water supply, sewage or telecommunications services. As such, these areas may require a resupply or evacuation.

Overland Refuge Areas

Overland refuge areas provide an area for flood-affected areas of the floodplain to be evacuated to, but are isolated from the edge of the floodplain by floodwaters. These areas are essentially flood islands or trapped perimeter areas and should be categorised accordingly to determine their vulnerability during flood events.

6.2.1 Classification of FERP Communities for Fairfield CBD The classification of communities for Flood Emergency Response Planning (FERP) is typically undertaken at a broad or precinct scale to assess relative vulnerability of the community in flood emergency response. However, for the Fairfield CBD catchment Council has requested the mapping to be undertaken at a lot scale. There is considerable detail at lot scale to consider with respect to availability of road/pedestrian evacuation routes from individual properties, the timing and severity (flood hazard) of flood inundation with respect to route closure.

The FERP classifications for the 1% AEP and PMF events are shown in Figure 6-1 and Figure 6-2 respectively. The key consideration in the mapping is the availability of evacuation routes. The urban overland flooding regimes are complex in this regard with a high degree of variability in flood hazard (depth and velocity) typically along any given vehicular or pedestrian route. Relative timing and duration of inundation can also be variable. The mapping shown adopted a somewhat conservative approach in assessing trafficability of roads for vehicular access and availability of pedestrian routes. The flood inundation and hazard classifications at the peak of the flood event were typically used to assess access routes. This recognises the typically flashy nature of the catchment in that peak flooding conditions may be reached very quickly from the onset rainfall in



the major events. Accordingly, this may limit the response time of individuals within the catchment to make appropriate evacuation choices.

Access roads were considered to be not suitable for vehicle evacuation when the hazard class was H2 (unsafe for small vehicles) and above. Pedestrian routes were considered non-viable for hazard class H3 (unsafe for all vehicles, children and the elderly) and above.

Being a relatively small urban catchment, the typical duration of inundation within the Fairfield CBD catchment would be short, typically 1-2 hours. The duration of peak flooding conditions affecting evacuation and flood access may be very short in some instances. Accordingly, isolation issues are likely not significant in the study. From a flood emergency response perspective therefore, the most critical classification within the CBD is the low flood island category. This identifies properties which may become isolated during a flood event with no available refuge above the PMF level.

In the Fairfield CBD catchment area, there are five zones where there is a concentration of low flood island properties as summarised below:

Hamilton Road – there are many properties adjacent to Hamilton Road with a low flood island classification. In major flood events, Hamilton Road is a significant overland flow path as shown in the mapping in Appendix A. Under PMF conditions, typical peak depths of flooding through the Hamilton Road corridor are in excess of 0.8m. The hazard mapping in Appendix A also provides for typically H4-H5 hazard classification.

Nelson St / Wrentmore Street Road – similar to Hamilton Road, the Nelson Street / Wrentmore Street corridor represents another significant west to east overland flow path through the catchment. Early closure of evacuation routes again coupled with high hazard flood conditions at the PMF level provide for a string of properties at high risk.

Fairfield CBD / commercial area – in major events, many of the access roads in the CBD area would be subject to inundation particularly with the convergence of the Hamilton Road and Wrentmore Street flow paths. The broader CBD area also lies within the backwater influence of the railway embankment. Accordingly, under PMF conditions, flood depths may rise considerably in this area prior to overtopping of the railway. The majority of properties in the CBD area are two-storey, however, the mapping has not considered the configuration of buildings and general availability to access higher floors. A more detailed investigation of this may be considered in future assessments.

Railway Parade – under PMF conditions, the backwater influence of the railway embankment provides for high hazard flood conditions along Railway Parade adjacent to the embankment. Dependent on the rate of rise in these areas, pedestrian evacuation particularly in PMF conditions may not be possible.

Wilga Street – the Wilga Street corridor represents the major overland flow path for floodwater overtopping the railway embankment under PMF conditions. Floodwaters at high depth and velocity can move through this corridor towards Orphan School Creek.



Figure 6-1 1% AEP Flood Emergency Response Classification



Figure 6-2 PMF Flood Emergency Response Classification

Fairfield CBD Floodplain Risk Management Study and Plan 49


Coordinated evacuation from any of these areas is unlikely given the flashy nature of flooding with self-directed evacuation the reality. As noted in the FERP mapping, there is a high potential for property isolation due to evacuation/access routes being cut, potentially early in an event or with minimal warning time. This reinforces the potential need for a shelter in place option with appropriate planning conditions.

6.3 Flood Education Flood education is a key emergency management response measure in educating the community relating to flood risk, evacuation, preparation, insurances and flood mitigation. Through the community consultation, 64% of respondents indicated they would not know how to protect themselves or their property during flooding events and 98% had not prepared a plan for their household or business to follow during an event. Furthermore, 73% of respondents had never seen or heard of information relating to flooding in the area. This information bolsters the requirement for a community flood education program to assist in flood preparedness and awareness.

In 2012, Molino Stewart was engaged to undertake Council’s Flood Education and Awareness Project for Fairfield City. As part of the program, data was collected via survey to determine the level of flood awareness and preparedness. Challenges for community flood education were identified to be the large cultural and lingual diversity in the local population. Over 20% of the population within the suburb of Fairfield speak a language other than English and do not speak English well or at all. As such, flood education programs for the Fairfield community need to recognise the cultural and linguistic diversity and cater for these needs, particularly those part of vulnerable cohorts. Education programs, including verbal and written material, should be conducted in multiple languages to increase public safety, reduce property damages and increase the recovery of flood-affected communities.

As noted in the Flood Preparedness Manual (Attorney-General’s Department, 2009), planning for floods requires a sound understanding of the flood threat to the community, knowledge of flood hazards and the impacts of flood events. Therefore, community education programs need to focus on conveying the current and future flood risk on a local level (including individuals understanding the risk to their properties), assist in the preparation of flood emergency plans, and ensure that the population understands what is required of them and the relevant emergency organisations during flood events. As stated, this information needs to be delivered in multiple languages and in both verbal and written information available face-to-face, directly to vulnerable residents, online and in commonly accessed businesses/organisations around the community.

Fairfield CBD Floodplain Risk Management Study and Plan 50 Property Inundation and Flood Damages Assessment


7 Property Inundation and Flood Damages Assessment A flood damage assessment has been undertaken to identify flood affected property, to quantify the extent of damages in economic terms for existing flood conditions and to enable the assessment of the relative merit of potential flood mitigation options by means of benefit-cost analysis.

The general process for undertaking a flood damages assessment incorporates:

identifying properties subject to flooding

determining depth of inundation above floor level for a range of design event magnitudes

defining appropriate stage-damage relationships for various property types/uses

estimating potential flood damage for each property, and

calculating the total flood damage for a range of design events.

7.1 Property Data Assessment of flood damages requires compilation of a spatial database containing information on the location, elevation and type of built assets vulnerable to flood impacts. Existing property floor level information for a number of the flood affected properties (residential, commercial and industrial) within the catchment has been previously surveyed by Council. This information was used to develop a database of potentially flood affected assets.

7.1.1 Location Property locations have been derived from Council’s cadastre information and associated detailed aerial photography of the catchment. Linked within a GIS system, this data enables rapid identification and querying of property details.

A property database has been developed detailing individual properties subject to flood inundation. For the purposes of the flood damage assessment, property was considered as either residential or commercial.

7.1.2 Ground and Floor Levels There are a number of potentially flood affected properties within the catchment that are not captured by Councils existing floor survey database. These additional properties were mapped for this study in GIS, based on an assessment of aerial photography and available spatial information (cadastre, LEP maps etc). Of the total 1199 properties identified within the PMF extent, 880 properties have detailed floor level survey information, while the remaining 319 properties do not.

Ground levels for all properties surveyed by Council were extracted from the high resolution (LiDAR) digital elevation model (DEM) available for the study catchment. Information on the typical height of floor level above ground level is shown in Figure 7-1 and Table 7-1. Height of floor levels above ground are varied throughout the catchment with a median above ground height of 0.42 m. Approximately 25% of the surveyed floor levels are between 0.2 to 0.4 m above the ground level and the same proportion of surveyed levels range between 0.4 to 0.6 m above the ground. A significant proportion of surveyed properties have floor levels between ground level and 0.2 m



above the ground, and a small proportion to properties have floor levels 2.2 and 3.8 m above the ground (see Figure 7-1). The surveyed floor levels greater than 2.6 m were found to mostly occur within high density residential areas or adjacent to the flood prone St Elmos Drain.

Table 7-1 Floor Level Statistics for Available Property Survey Information

Minimum* Median Mean Standard Deviation

Maximum

Floor Level (m) above Ground

0 m 0.43 m 0.57 m 0.66 m 6.12 m

* Some floor survey levels sit below the corresponding LiDAR DEM ground level. This likely indicates an error in the LiDAR DEM. For these survey points, the ground level has been adopted as the floor survey level to calculate the above statistics.

Figure 7-1 Distribution of Surveyed Flood Levels within the Fairfield CBD catchment

7.1.3 Flood Level The flood modelling results were used to generate a continuous flood profile across the floodplain. Flood levels calculated from the TUFLOW model were queried from TUFLOW’s GIS output at each property reference point. The resulting output was used to identify flooding characteristics such as the number and type of properties affected, frequency of inundation and the depth of inundation.

7.2 Property Inundation A summary of the number of properties potentially affected by above floor flooding for a range of flood magnitudes is shown in Table 7-2. The table distinguishes flooding between residential property and industrial/commercial enterprise.

0

50

100

150

200

250

Prop

erty

Cou

nt

Surveyed Floor Level above LiDAR Ground Level (m)

Floor levels >2.2 m generally occur in high density residential zoned areas, or adjacent the lower reaches of St Elmos Drain



Table 7-2 Number of Flood Affected Properties

Design Flood Event

Residential Properties with Above Ground

Flooding

Residential Properties with

Above Floor Flooding

Commercial Properties with Above Ground

Flooding

20% AEP 38 0 1

5% AEP 71 1 3

1% AEP 112 4 15

PMF 424 324 230

Key areas at risk of above floor flooding up to the 1% AEP event include:

properties on and around Barbara Street and mostly between Hamilton Road to Harris Street. This area is where the two main flowpaths upstream of the railway line converge. Flood impacts also become accentuated in this region under the 1% AEP design event (and greater) due to the Barbara Street rail culvert reaching capacity.

business properties located at the northern end of Ware Street, upstream of Nelson Road, due to local drainage issues associated with a raised road crest.

properties located toward the downstream limit of the catchment, on the low-lying floodplains adjacent to Prospect Creek and Orphan School Creek. Flooding experienced here is driven by mainstream flood processes (as opposed to overland flooding); and

a number of isolated properties located on the main flowpaths (i.e. Nelson to Wrentmore Street flowpath and Hamilton Road flowpath upstream of the railway) or secondary/tertiary flowpaths (i.e. near Austral Parade and The Crescent, upstream of the railway and the Wilga Street flowpath which flows into St Elmos Drain).

A considerably greater number and distribution of properties may experience above floor inundation under the PMF design event.

7.2.1 Public and Private Assets A range of public and private assets, infrastructure and land exist within the catchment, which have been mapped in Figure 7-2 and listed in Table 7-3. These assets generally fall into the following categories:

public services;

public recreation;

private recreation;

community buildings;

aged care facilities;

shopping centres;



infrastructure – water, wastewater, electricity

infrastructure – railway, arterial roads, main roads

schools, preschools, childcare etc; and

churches / Places of worship.

A relative assessment of flood risk to these identified public and private assets has been completed as part of this study. This high-level assessment of risk has given consideration to the likelihood of a flood impact occurring (e.g. 20% AEP, 1% AEP and PMF events) in addition to the consequence of the impact (flash flooding of a park would have an insignificant impact relative to flooding of an electrical substation which would have a major impact, for example; the depth and velocity of flooding also influences the flood impact consequence to any given asset type). Low and medium levels of risk may be considered acceptable and therefore not require immediate action. In comparison, high and extreme levels or risk should be considered intolerable and therefore require action of some kind (flood mitigation works, development controls, emergency management planning etc.).

Table 7-3 Public and Private Assets within the Fairfield CBD 1% AEP and/or PMF extent

# Public and Private Asset in PMF # Public and Private Asset in PMF

School (including preschool/childcare) Aged Care Facility

1 Our Lady of the Rosary Primary School 10 Fairfield Nursing Home

2 First Grammar Fairfield Childcare Public Service

3 Fairfield Heights World of Learning 11 Fairfield Police Station

4 Care 4 Kids 12 Fairfield Court House

5 Imaginations Preschool & ELC Shopping Centre

6 KU Fairfield AMEP Child Care Centre 29 Fairfield Forum

7 Fairfield Nursery School 30 Neeta Shopping Centre

8 Tweety FDC Scheme Infrastructure

9 Hilal Family Day Care Scheme 13 Fairfield Railway Station

28 Warakirri College 23 Fairfield Wastewater Treatment Plant

Public Recreation 24 Fairfield Sewerage Pump Station

15 Fairfield Library 25 Fairfield Electrical Station

16 Fairfield City Leisure Centre 26 Horsley Drive

17 Fairfield Park Tennis Complex 27 Cabramatta-Granville Railway

18 Fairfield Park Private Recreation

19 Fairfield Heights Park 14 Fairfield RSL

20 Nelson Park 22 Mounties Bowling Club

21 Kinta Park



7.2.2 High Risk Assets The flood hazard within the Fairfield CBD catchment is typically low relative to other nearby catchments due to the small flood depths and limited flooding footprints modelled for the 1% to 20% AEP design events. The vast majority of public and private assets located within the Fairfield CBD floodplain are impacted by the PMF design event only, or else are impacted by the 1% AEP with a minor to moderate consequence (e.g. flooding below floor level, access only partially impacted). However, a small number of public and private assets have been identified with a high flood risk due to the nature of the potential flood impact. These include:

Fairfield Forum (shopping centre);

Fairfield Nursing Home (aged care facility); and

Fairfield Electrical Station (essential infrastructure).

Flooding under the 1% AEP design condition may potentially impact the ground floor loading dock area of the Fairfield Forum shopping centre that borders with Cunninghame Street and Nelson Street. Such conditions would be expected to cause widespread and significant damage to both the shopping centre building and also the shopping centre stock stored within the impacted area. For this reason, a high flood risk level has been flagged. Flooding is not considered to pose a significant risk to human safety at Fairfield Forum shopping centre under the 1% AEP design condition, as large areas of the adjoining carparks and shopfronts on the southern and western sides are not impacted by floodwaters. Access to and from the shopping centre is not restricted in a 1% AEP design flood event and there is good opportunity for affected persons to walk to dry ground.

Fairfield Nursing Home located on The Crescent in Fairfield will be impacted by flooding under the 1% AEP condition, where the design flood waters are modelled to reach the floor level of the aged care facility. Under a 1% AEP event, all road and foot access into and out of the Fairfield Nursing Home is impacted/restricted. Considering elderly and typically fragile/less mobile nature of the people residing in the nursing home, the 1% AEP flood impact is considered to pose a significant safety risk. For this reason, a high flood risk has been assigned to the Fairfield Nursing Home.

The Fairfield Electrical Station is also susceptible to flooding impacts, however the degree of potential impact needs to be confirmed. The electrical station is located at East Parade, near Symons Street, on sloping ground. Low-lying areas containing infrastructure within the property boundary become impacted by flooding under events equal to or greater than a 20% AEP design condition. The ground level building is located on higher ground and not impacted by floodwater under the PMF event. Considering the essential service the electrical station provides and the current knowledge gap regarding infrastructure heights and potential impacts, a high flood risk has been assigned to the Fairfield Electrical Station. This risk rating may be revised and downgraded once detailed survey information or design advice is obtained for this asset.



Figure 7-2 Potential Flood Affected Properties within Overland 1% AEP and PMF Extent



7.3 Flood Damages Assessment

7.3.1 Types of Flood Damage The definitions and methodology used in estimating flood damage are summarised in the Floodplain Development Manual. Figure 7-3 summarises the “types” of flood damages as considered in this study. The two main categories are 'tangible' and 'intangible' damages. Tangible flood damages are those that can be more readily evaluated in monetary terms, while intangible damages relate to the social cost of flooding and therefore are much more difficult to quantify.

Tangible flood damages are further divided into direct and indirect damages. Direct flood damages relate to the loss, or loss in value, of an object or a piece of property caused by direct contact with floodwaters. Indirect flood damages relate to loss in production or revenue, loss of wages, additional accommodation and living expenses, and any extra outlays that occur because of the flood.

Figure 7-3 Types of Flood Damage



7.3.2 Residential Flood Damages

Flood damages have been calculated using the data base of potentially flood affected properties and a number of stage-damage curves derived for different types of property within the catchment. These curves relate the amount of flood damage that would potentially occur at different depths of inundation, for a particular property type.

Residential damage curves are based on the OEH guideline stage-damage curves for residential property. There are different damage curves for low set single storey houses, high set single storey houses (i.e. those with ground floor levels more than 1.5m above ground level) and two storey houses which account for the different depths of flooding necessary for contents to be damaged.

The standard damage curves have been adjusted based on a number of parameters specific to the Fairfield CBD catchment as summarised in Table 7-4.

Table 7-4 Residential Damage Curve Inputs

Variable Value Comment

Regional Cost Variation factor 1.0 from Rawlinsons

Post late 2001 adjustments 1.75 Changes to average

weekly earnings (ABS data)

Post Flood Inflation Factor 1.0 Regional City small scale impact

Typical Duration of Immersion 2hrs Short duration flooding

Building Damage Repair Limitation Factor 0.85 Short duration

Typical House Size 190m2 Sample of houses within catchment

Contents Damage Repair Limitation Factor 0.75 Short duration

Level of Flood Awareness Low Community survey results

Effective Warning Time 0hr Flash flooding

Typical Table/Bench Height 0.9m Standard

External Damage $6,700 Standard

Clean-up costs $4,000 Standard

Likely Time in Alternative Accommodation 2 weeks Assumed

Additional Accommodation Costs $220/week Standard

The adopted residential depth-damage curves are presented in Appendix D.

The depth-damage curves incorporate a damage allowance for flood depths below floor level. This reflects potential for external property damage when the water level is below floor level (e.g., damage to fences, sheds, belongings stored below the building floor). In much of this urban



overland flow environment, it is considered unlikely the typically shallow depth of flow generated along overland flow paths would result in extensive damage to property. For external damages where the flood depth is below 0.3 m and no above floor inundation occurs, a nominal $1,000 value has been adopted. Above the 0.3m depth the standard external damage costs are applied.

Tangible indirect damages are the costs and losses incurred as an indirect consequence of the flooding and can include clean-up costs, temporary accommodation, additional travel, lost income, health costs etc. It is noted that the OEH residential stage-damage curves make allowance for both cleanup costs ($4,000 per flooded house) and the cost of time in alternative accommodation. Nevertheless, a further measure of indirect damages has been estimated by taking 20% of the total direct damages, which is consistent with the approach in the Prospect Creek Floodplain Risk Management Study.

7.3.3 Commercial Flood Damages There are no standard stage-damage curves for commercial and industrial damages. For consistency, the stage-damage relationships used to estimate these damages in this study are based on those previously adopted for the Georges River, Cabramatta Creek and Prospect Creek Floodplain Risk Management Studies completed by Bewsher Consulting.

For commercial/industrial land uses, the type of activity was split into one of six codes according to the value of the contents (i.e., low, medium and high damage potential).

Commercial low (CL)

Commercial medium (CM)

Commercial high (CH)

Industrial low (IL)

Industrial medium (IM)

Industrial high (IH)

The adopted commercial depth-damage curves are presented in Appendix D.

Similar to the approach for residential damages, indirect commercial/industrial losses were estimated as 20% of direct actual commercial/industrial damages. This is consistent with the approach in the Prospect Creek Floodplain Risk Management Study.

7.3.4 Infrastructure and Public Sector Damages Public utilities and infrastructure include roads, railways, parklands and underground water, sewerage, power and telephone services and installations. The damages sustained by public utilities comprise the replacement or repair of assets damaged by floodwaters, the cost of clean-up of the installations as well as the collection and disposal of clean-up material from private property.

Damage incurred to public utilities and infrastructure during a flood event was estimated as 30% of the combined tangible (direct and indirect) damages to residential and commercial properties. This is consistent with the approach in the Prospect Creek Floodplain Risk Management Study.



7.3.5 Intangible Damages Intangible damages relate to the social impact of flooding and include:

○ inconvenience,

○ isolation,

○ disruption of family and social activities,

○ anxiety, pain and suffering, trauma,

○ physical ill-health, and

○ psychological ill-health.

The damage estimates derived in this study are for the tangible damages only. Whilst intangible losses may be significant, these effects have not been quantified due to difficulties in assigning a meaningful dollar value.

7.4 Damages Summary The peak depth of flooding was determined at each property for the 20% AEP, 5% AEP, 1% AEP and PMF design events. The associated direct flood damage cost to each property was subsequently estimated from the stage-damage relationships.

The Average Annual Damage (AAD) is the average damage in dollars per year that would occur in a designated area from flooding over a very long period of time. In many years there may be no flood damage, in some years there will be minor damage (caused by small, relatively frequent floods) and, in a few years, there will be major flood damage (caused by large, rare flood events). Estimation of the AAD provides a basis for comparing the effectiveness of different floodplain management measures (i.e. the reduction in the AAD).

The assessment of the residential flood damages is presented in Table 7-5. From this data, the AAD for residential properties was calculated as being $74,000 in total damages

Table 7-5 Summary of Residential Flood Damages

Event Magnitude

Properties Flooded Above Floor (and

Ground) Direct Damages

($) Indirect

Damages ($) Total Damages

($)

20% AEP 0 (38) $38,000 $7,600 $45,600

5% AEP 1 (71) $139,000 $28,000 $167,000

1% AEP 4 (112) $348,000 $20,000 $367,000

PMF 324 (424) $21,858,000 $1,260,000 $23,118,000 AAD for all

Floods $70,000 $4,000 $74,000

The assessment of the commercial flood damages is presented in Table 7-6. From this data, the AAD for commercial properties was calculated as being $103,000 in direct damages and $41,000 in indirect damages, giving a total value of $144,000 for all affected commercial properties.



Table 7-6 Summary of Commercial Flood Damages

Event Magnitude

Properties Flooded Above Floor (and

Ground) Direct Damages

($) Indirect

Damages ($) Total Damages

($)

20% AEP 1 (1) $11,000 $4,000 $15,000

5% AEP 3 (10) $80,000 $32,000 $112,000

1% AEP 15 (27) $1,009,000 $404,000 $1,413,000

PMF 230 (90) $36,861,000 $14,744,000 $51,605,000 AAD for all

Floods $103,000 $41,000 $144,000

The total tangible flood damages for residential and commercial properties and the damage to public utilities were combined, as presented in Table 7-7. From this data, the combined AAD was calculated as being $298K comprised as follows:

$85K from residential properties;

$145K from commercial properties; and

$68K from public utilities.

Table 7-7 Summary of Total Tangible Flood Damages

Design Event Residential Flood Damages ($)

Commercial Flood Damages

($)

Public Utilities Flood Damages

($) Total Tangible Flood

Damages ($)

20% AEP $46,000 $15,000 $18,000 $79,000

5% AEP $167,000 $112,000 $84,000 $362,000

1% AEP $367,000 $1,413,000 $549,000 $2,330,000

PMF $23,118,000 $51,605,000 $23,350,000 $98,073,000

AAD $85,000 $145,000 $68,000 $298,000

Fairfield CBD Floodplain Risk Management Study and Plan 61 Review of Existing Planning Provisions


8 Review of Existing Planning Provisions Land use planning and development controls are key mechanisms by which Council can manage some of the flood related risks within flood-affected areas in Fairfield CBD catchment (as well as across the wider Local Government Area (LGA)).

A review of existing planning controls has been undertaken with the objective being to:

review the existing planning and development controls framework relevant to the formulation of planning instruments and the assessment of development applications in the Fairfield CBD floodplain, and

make specific planning recommendations in regard to flood risk management, including an outline of suggested planning controls.

8.1 Local Environment Plan A Local Environmental Plan (LEP) is prepared in accordance with Part 3 Division 4 of the EP&A Act 1979 and operates as a local planning instrument that establishes the framework for the planning and control of land uses. The LEP defines zones, permissible land uses within those zones, and specific development standards and special considerations with regard to the use or development of land.

The Fairfield Local Environmental Plan 2013 (FLEP 2013) has been prepared in accordance with the NSW State Government’s Standard Instrument (Local Environmental Plans) Order 2006, which requires local Councils to implement a Standard Instrument LEP. The State Government has created the Standard Instrument LEP to assist in streamlining the NSW Planning system.

Part 6 of the LEP allows Councils to include clauses that address local circumstances within the City. Local provisions are detailed for the following issues:

acid sulfate soils

earthworks

flood planning

floodplain risk management

terrestrial biodiversity

riparian land and watercourses

landslide risk

infrastructure development – Council

essential services

Clause 6.3 Flood planning of the FLEP 2013 relates to flood planning for flood liable land and outlines provisions to minimise risk to life and property from flooding, allow development compatible with the land’s flood hazard, and avoid adverse impacts on flood behaviour and the environment up to the FPL. Specifically, Clause 6.3 states:



(1) The objectives of this clause are as follows:

a. to minimise the flood risk to life and property associated with the use of land,

b. to allow development on land that is compatible with the land’s flood hazard, taking into account projected changes as a result of climate change,

c. to avoid significant adverse impacts on flood behaviour and the environment.

(2) This clause applies to land at or below the flood planning level.

(3) Development consent must not be granted to development on land to which this clause applies unless the consent authority is satisfied that the development

a. is compatible with the flood hazard of the land, and

b. will not significantly adversely affect flood behaviour resulting in detrimental increases in the potential flood affectation of other development or properties, and

c. incorporates appropriate measures to manage risk to life from flood, and

d. will not significantly adversely affect the environment or cause avoidable erosion, siltation, destruction of riparian vegetation or a reduction in the stability of river banks or watercourses, and

e. is not likely to result in unsustainable social and economic costs to the community as a consequence of flooding.

(4) A word or expression used in this clause has the same meaning as it has in the ‘Floodplain Development Manual (ISBN 0 7347 5476 0)’ published by the NSW Government in April 2005, unless it is otherwise defined in this clause.

(5) In this clause, flood planning level means the level of a 1:100 ARI (average recurrent interval) (equivalent to the 1% AEP) flood event plus 0.5 metre freeboard.

Clause 6.4 Floodplain risk management of the FLEP 2013 relates to floodplain risk management and outlines provisions to enable planning for evacuation of land subject to flooding above the FPL and plan for the protection of the operational capacity of critical facilities and infrastructure. Specifically, Clause 6.4 states:

(1) The objectives of this clause are as follows:

a. in relation to development with particular evacuation or emergency response issues, to enable evacuation of land subject to flooding in events exceeding the flood planning level,

b. to protect the operational capacity of emergency response facilities and critical infrastructure during extreme flood events.

(2) This clause applies to land between the flood planning level and the level of a probable maximum flood, but does not apply to land subject to the discharge of a 1:100 ARI (average recurrent interval) (equivalent to the 1% AEP) flood event plus 0.5 metre freeboard.

(3) Development consent must not be granted to development for the following purposes on land to which this clause applies unless the consent authority is satisfied that the development will



not, in flood events exceeding the flood planning level, affect the safe occupation of, and evacuation from, the land

a. caravan parks,

b. commercial premises,

c. correctional centres,

d. emergency services facilities,

e. group homes,

f. hospitals,

g. industries,

h. residential accommodation,

i. residential care facilities,

j. tourist and visitor accommodation.

(4) In this clause:

flood planning level means the level of a 1:100 ARI (average recurrent interval) (equivalent to the 1% AEP) flood event plus 0.5 metre freeboard.

probable maximum flood has the same meaning as it has in the ‘Floodplain Development Manual (ISBN 0 7347 5476 0)’, published in 2005 by the NSW Government.

8.1.1 Land Use The FLEP 2013 identifies a number of land use zones based on stated objectives for each zoning and provisions made for each zoning. The land use zones under the FLEP 2013 are as follows:

Rural Zones: RU1 Primary Production, RU2 Rural Landscape, RU4 Primary Production Small Lots and RU5 Village;

Residential Zones: R1 General Residential, R2 Low Density Residential, R3 Medium Density Residential and R4 High Density Residential;

Business Zones: B1 Neighbourhood Centre, B2 Local Centre, B3 Commercial Core, B4 Mixed Use, B5 Business Development and B6 Enterprise Corridor

Industrial Zones: IN1 General Industrial and IN2 Light Industrial;

Special Purpose Zones: SP1 Special Activities, SP2 Infrastructure and SP3 Tourist;

Recreation Zones: RE1 Public Recreation and RE2 Private Recreation;

Environment Protection Zones: E2 Environmental Conservation and E3 Environmental Management; and

Waterway Zones: W2 Recreational Waterways.



Within the Fairfield CBD Floodplain Risk Management Study area much of the flood affected land is classified as R2, R3 R4 (Low to High Density Residential) and B4 (Mixed Use). Areas zoned as SP1, SP2 (Special Purpose Zones, for Sewerage, Electricity, Railway and Classified Roads), RE1 (Public Recreation) and E2 (Environmental Conservation) are also affected by floods (see Figure 8-1.

8.2 Development Control Plan Council has adopted planning controls covering flood prone land in accordance with the NSW Flood Development Manual (2005) and the NSW Flood Prone Land Policy. The primary objective of the controls is to reduce the impact of flooding and flood liability on individual owners and occupiers of flood prone property, and to reduce private and public losses resulting from floods, utilising ecologically positive methods wherever possible”. (Fairfield City Council Website, viewed November 2016). These controls are outlined in the Citywide Development Control Plan 2013 (Citywide DCP 2013), with additional planning controls in relation to stormwater management provided in the Fairfield City Centre DCP 2013 (City Centre DCP 2013).

A Development Control Plan (DCP) is prepared in accordance with Section 72 of the Environmental Planning and Assessment Act 1979 and Clauses 16 to 25 of Part 3 of the Environmental Planning and Assessment Regulation 2000. A DCP effectively complements an LEP by providing more detailed provisions with respect to development in particular areas, and is to be considered by Council in determining development applications. Flood related planning controls that apply to all flood prone land within Council are outlined in the Citywide DCP 2013 and summarised in Section 8.2.1. Additional flood planning controls specific to the city centre are outlined in the City Centre DCP 2013 and summarised in Section 8.2.2.

8.2.1 Fairfield Citywide Development Control Plan 2013 The Citywide DCP 2013 applies to all land in Fairfield City Council. This Plan combined various policies and guideline that affecting development proposals, and supplements the FLEP 2013. Flood related controls outlines in the Citywide DCP 2013 are summarised below.

8.2.1.1 Chapter 2 Development Application Process: Step 3 Prepare Statement of Environmental Effect and other required plans or reports Chapter 2 describes Council’s requirements for the submission of development application, including the requisite for proposed developments on flood prone land to submit a Flood Risk Management Report. Clause 2.5.9 details the procedure to determine what controls apply to a parcel of land, and also the steps required to complete a Flood Risk Management Report. This clause also flags that a Flood Impact Assessment may be required where flood impacts to adjoining properties from the proposed development may occur.



Figure 8-1 Fairfield CBD Land Use Zones



8.2.1.2 Chapter 3 Environmental Management and Constraints: Flood Risk Management Chapter 3 provides controls with respect to natural environment and provides guidance for development affected by flood risk assessment. Prescriptive steps that need to be followed for development application in relation to flood risk analysis and management are provided, which are summarised in Figure 8-2 below.

Figure 8-2 Flood Risk Assessment Processes for DA’s (Citywide DCP 2013)

8.2.1.3 Chapter 11 Flood Risk Management Chapter 11 initially provides a context and background to floodplain risk management based on the NSW Flood Prone Land Policy and the associated floodplain risk management process. Objectives for floodplain risk management in Fairfield are listed.

A series of performance criteria and prescriptive criteria are outlined that are intended to achieve the stated objectives. The prescriptive criteria are shown as a set of development control matrices which serve to marry specific development controls with various land use categories for three flood risk precincts. Figure 8-3 below shows the development control matrix from the DCP that is currently being applied to development in the Fairfield CBD catchment.

Development types associated with land use categories are listed in schedule 2 within the chapter.

The following three flood risk precincts have been defined within the DCP:

high flood risk precinct: Land below the 1% AEP flood that is subject to a high hydraulic hazard or where there are significant evacuation difficulties

medium flood risk precinct: Land below the 1% AEP flood that is not within a high flood risk precinct

low flood risk precinct: Land up to the PMF that is not within the high or medium flood risk precinct.

In addition to the above, the DCP contains useful information related to definitions, assessment requirements, special requirements for fencing, flood compatible building materials and components and explanation of controls related to car parking.



Figure 8-3 Development Control Matrix for Local Overland Flooding (Citywide DCP 2013)



8.2.2 Fairfield City Centre Development Control Plan 2013 The City Centre DCP 2013 was prepared to implement the vision identified in the Fairfield City Centre Strategic Plan, and applies to land located within the Fairfield City Centre Boundary as identified in Figure 8-4 below. This DCP recognises that some parts of the City are affected by overland flowpaths and some by flooding from the creek.

Figure 8-4 Fairfield City Boundary to which the City Centre DCP 2013 applies

This City Centre DCP 2013 adopts a number of provisions contained within the Citywide DCP 2013, including the flood related development controls outlined in Chapter 2, Chapter 3 and Chapter 11 (see Section 8.2.1 for a summary of these controls).

Additional flood related controls outlined in the City Centre DCP 2013 are outlined below.

Fences and Walls Design Controls:

(h): Open type fences to be constructed within flood prone or overland flow areas.

Stormwater Management Controls:

(a) Submit a storm water concept plan in accordance with Council’s On-Site Detention Policy and/or Floodplain Risk Management Study and Plan with each Development Application.



(b) Ensure the development does not impact on existing overland flowpaths, flood storage, or flood levels on adjoining properties.

(e) Some sites in the City centre may be flood affected and a flood study may be required to be submitted with your application. (Note: Council has exhibited a Draft DCP for all flood liable land and any development will be required to comply with this Council DCP).

(f) Set floor levels with freeboard of at least 300 mm above the 1 in 100 year (1% AEP) water surface levels of the basin. The properties affected by overland flowpaths and creek flooding require a different freeboard subject to further investigations/calculations which need to be submitted.

8.2.3 Section 149 Planning Certificates A 149 Certificate is a planning certificate issued under Section 149 of the EP&A Act by Councils. The 149 Certificates give information on town planning controls applying to a nominated parcel of land and other information which may affect the use or development of the land. The two types of 149 Planning Certificates, and the associated flood planning information contained within those certificates specific to Fairfield City Council, are summarised below.

Section 149 (2) certificates provide flood planning information in the form of a Flood Notation. The Flood Notation provides details on Council’s flood policy. This certificate provides mainstream and overland flood risk precincts for the identified properties if affected.

Section 149 (5) certificates provides a Flood Information Sheet for flood affected properties in addition to the information provided in their Section 149 (2) certificate. The Section 149 (5) includes specific details on flood risks and planning controls specific to the associated property. The Flood Information Sheet identifies: if part or all of the property land may be affected by mainstream and/or overland flooding, the associated level of flood risk in relation to each specific type of flood (i.e. mainstream or overland) and its associated design flood levels.

8.2.4 Stormwater Drainage Policy 2017 Fairfield City Council’s Stormwater Drainage Policy provides additional detail to support the controls for stormwater drainage given in the Citywide DCP 2013 and City Centre DCP 2013. This includes site planning considerations, design requirements, connections to Council’s stormwater drainage systems and details on the approval process.

The following specific controls in the policy are considered relevant for this catchment management plan:

Freeboards: Floor levels to have 300 mm freeboard above the finished ground level or the 100 year ARI (1% AEP) level of the overland flowpath (freeboards for flood affected properties are to comply with flood related development controls in the DCP). Garage floor levels and underside of solid fencing to have 100 mm freeboard from finished ground level or the 100 year ARI (1% AEP) level of the overland flowpath.



Impervious Area Percentage: Maximum percentage impervious area for development other than commercial or industrial, is 70%. There is no maximum percentage area if OSD is installed.

Pump-Out Systems: Not supported for residential development excluding secondary dwellings permitted for commercial and industrial developments.

Adsorption Trenches: Infiltration trenches are permitted for hardstand area less than 50 m2 subject to certain design requirements.

The policy notes that commercial and industrial developments must implement water saving measures and devices and reuse water onsite.

Fairfield CBD Floodplain Risk Management Study and Plan 71 Potential Options for Improving Flood Management


9 Potential Options for Improving Flood Management This chapter identifies options for improving flood management within Fairfield CBD with respect to existing flood risks, future flood risks, and continuing flood risks. Measures which can be employed to mitigate flooding and reduce flood damages can be separated into three broad categories:

flood modification measures: modify the flood’s physical behaviour (depth, velocity) and includes flood mitigation dams, retarding basins, on-site detention, channel improvements, levees, floodways or catchment treatment.

property modification measures: modify property and land use including development controls. This is generally accomplished through such means as flood proofing (house raising or sealing entrances), planning and building regulations (zoning) or voluntary purchase.

response modification measures: modify the community’s response to flood hazard by informing flood-affected property owners about the nature of flooding so that they can make informed decisions. Examples of such measures include provision of flood warning and emergency services, improved information, awareness and education of the community and provision of flood insurance.

The following sections also provide a first pass assessment of options by determining if they would be applicable / suitable to the flooding environments of Fairfield CBD.

9.1 Flood Modification Measures Flood modification measures are designed to modify or manipulate the behaviour of the flood, either by changing its passage (redirection of flowpaths) or its characteristics of flow depth and velocity. Typical flood modification measures considered where significant flood risks exist include:

modifications measures to exclude floodwaters, such as permanent levees or walls, temporary sandbags, floodgates;

modification measures to contain floodwaters, including flood mitigation dams and detention basis, and increased floodplain storage; and

modification measures to enhance conveyance or divert floodwaters, by flow diversion channels, stormwater drainage improvements, floodwater pump outs and removal of flow impediments.

The majority of the above listed measures are not appropriate considering the overland flooding mechanism being addressed in this report and the relatively low level of risk associated with this type of flooding within the CBD catchment.

In identifying potential flood modification measures for the Fairfield CBD overland catchment, focus is given to the relatively localised hotspot areas identified in Section 4.1.1 where above floor flooding may occur. These include:

business properties in immediately upstream of the Nelson Street and Ware Street intersection; and



residential and business properties on and around Barbara Street, immediately upstream of the railway;

residential properties on Orchard Road and Riverview Road, adjacent to Prospect Creek and Orphan School Creek, located at the downstream limit of the CBD catchment.

Whilst the above locations are nominated as “hot spots”, property inundation within the catchment is highly localised to these areas. Broadly, overland flooding in the catchment is relatively shallow and poses little flood hazard as demonstrated in the previous sections. Given that above floor property inundation is highly limited in the catchment during the 1% AEP event and the largely developed nature of the catchment, there is not a need for major floodplain risk management works within the Fairfield CBD catchment. The nature of overland flooding in the catchment - in that it is shallow and of short duration - means that flood modification measures are unlikely to significantly alter the existing flooding conditions within the catchment. Notwithstanding the above, potential flood modification works to address above floor flooding at the hot-spot and overland flooding affecting property land are summarised below.

9.1.1 Overview of Options Whilst above floor inundation impacts from overland flooding are relatively restricted within the Fairfield CBD catchment, shallow overland flooding along the primary and secondary flowpaths affect a number of properties below floor level. A number of options to reduce property affection from shallow overland flooding are proposed in Table 9-1 (Options 4 to Option 12, noting Option 1 to Option 3 target above floor flooding as detailed in Section 9.1.2 to Section 9.1.4).

Figure 9-1 presents a summary figure that maps the location of all proposed flood modification measures. Figure 9-4 to Figure 9-27 provide additional information on each option location and associated option details.



Table 9-1 Potential Flood Modification Options

Option # Option Name Flooding Issues Option Details

Flood Modification Options

FM01 Nelson Street Stormwater Drainage Improvement See Figure 9-1 and Figure 9-2 Additional details provided in Sections 9.1.2

A small number of business properties are prone to above floor flooding behind the intersection of Ware and Nelsons Streets. Poor drainage conditions cause local ponding behind a high point in the centre of the intersection. Above floor inundation is simulated to occur at this area under a range of design events (20% AEP to PMF).

Improve drainage conditions immediately upstream of the Ware and Nelsons Street intersection. Drainage conditions may be improved through: a) Installation of additional

pits and pipes which target the area prone to ponding; and/or

b) Re-grading the road to remove the topographic high points, to allow overland flow to drain south into Ware Street.

FM02 Barbara Street / Hamilton Road Intersection Stormwater Drainage Improvements See Figure 9-1 and Figure 9-2 Additional details provided in Sections 9.1.3

A number of properties on and adjacent Barbara Street, upstream of Hamilton Road, have been identified at risk of above floor inundation under 1% design conditions due to water ponding behind highpoints along Hamilton Road. The flowpath immediately upstream of Hamilton Road tracks down an unnamed laneway between Barbara and Williams Streets before flowing onto Barbara Street. No stormwater drainage pits are located along the 1% AEP flowpath on the unnamed laneway. The local topographic controls on and adjacent Hamilton Road become overtopped in 1% AEP conditions, or greater.

Improve drainage conditions immediately upstream of Hamilton Road to reduce local ponding under 5% AEP design conditions. Local drainage conditions may be improved through: a) Installation of additional

pits and pipes targeting the area of ponding along the unnamed laneway, between Barbara and Williams Street; and/or

b) Regrading roadway high points that cause upstream ponding, including at the south end of the unnamed laneway and along Hamilton Road from the intersection of Barbara Street to the unnamed laneway.




FM03 Barbara Street Railway Culvert Upgrade See Figure 9-1 and Figure 9-2 Additional details provided in Section 9.1.4

The primary overland flowpaths converge on Barbara Street before draining downstream of the railway line via the Barbara Street Railway Culvert. This culvert reaches capacity under a range of flood conditions resulting in backwater flood impacts. In a 1% AEP design event, widespread backwater flooding upstream of the railway culvert along Barbara Street, between Railway Parade and Kenyon Street, causes above floor inundation of a number or residential and business properties.

Increase capacity of the Barbara Street Railway Culvert to reduce backwater flooding impacts to Barbara Street and adjoining areas.

FM04 Stormwater drainage improvements along Hamilton Road, between Eustace Street and Sackville Street See Figure 9-1 and Figure 9-2 Additional details provided in Section 9.1.5

Overland flooding along Hamilton Road forms one of the primary flowpaths upstream of the railway line. Shallow ‘nuisance’ flooding impacts a number of properties commencing at the 20% AEP event as the drainage system capacity is exceeded. Flows within the road network increase with the higher flood events road hazard and increasing flows through private property. The stormwater drainage system (pits/pipes) is located along the north side (only) of this road section.

Improve the stormwater drainage networks along Hamilton Road, between Eustace and Sackville Street, to reduce overland flooding by installing pits and pipes along the southern side of the road.




FM05 Stormwater drainage improvements along Hamilton Road, between Sackville Street and Thomas Street See Figure 9-1 and Figure 9-2 Additional details provided in Section 9.1.6

Shallow overland flooding impacts a number of residential properties on the northern side of Hamilton Road, downstream of Sackville Street starting from the 20% AEP event as drainage system capacity is exceeded. The main flowpath travels along Hamilton Road (and via the open concrete channel between Hamilton Road and Harris Street). Water spills from Hamilton Road into adjoining properties via low points along the road (e.g. drive way). No stormwater drainage is located along Hamilton Road between Sackville and Lackey Streets (with the exception of one pit).

Improve stormwater drainage networks along Hamilton Road, between Sackville and Thomas Street, to reduce overland flooding of adjoin properties. Install pits and pipes along the northern side of this road section. The above proposed stormwater network could either drain to the open concrete channel via an existing pipe at Thomas Street, or connect with existing pipe on Hamilton Road downstream of Lackey Street.

FM06 Improve efficiency of the railway culvert on Railway Parade (near Austral Parade) See Figure 9-1 and Figure 9-2 Additional details provided in Section 9.1.7

Overland flooding along Railway Parade, near Austral Parade, drains (in part) via a railway culvert. Water pools immediately upstream of this culvert under 20% AEP conditions with increasing inundation and depth for increasing flood event magnitudes.). Flow efficiency into the culvert is not optimal to local topographic constraints (i.e. high point in the road verge adjacent the culvert).

Regrade the area adjacent the railway culvert to ensure the surface water drains freely and efficiently into the culvert. This may include lowering the adjoining ground surface by 0.5m or so.

FM07 Improve surface drainage connection with St Elmos Drain in the vicinity of the Fairfield Recycled Water Plant See Figure 9-1 and Figure 9-3 Additional details provided in Section 9.1.8

Overland flow draining south of the railway line, via the Austral Parade/Railway Parade railway culvert, pools in and around the Fairfield Recycled Water Plant (WWTP) and nearby electrical substation Local topographic high points downstream of the WWTP and electrical substation restrict surface water from flowing freely into St Elmos Drain during the 5% AEP event and worse.

Improve surface drainage connectivity between the Austral Parade/Railway Parade railway culvert and St Elmos Drain through re-contouring the area of grassy/open space between the WWTP and the electrical substation.




FM08 Stormwater drainage improvements at Hale and Nelsons Streets (+/- redirecting surface flow along Hale and Nelson Streets, upstream of Sackville Street) See Figure 9-1 and Figure 9-3 Additional details provided in Section 9.1.9

The main northern overland flowpath, upstream of the railway, flows from Camden Street towards Barbara Street via Hale Place and surrounding residential properties (in addition to Nelson Street, Wrentmore Street and the intervening residential areas) during the 5% AEP event and worse. Stormwater drainage pits on and near Hale Place are not positioned on the main flowpath.

This option involves stormwater network improvements through: installing a new pit (and joining section of pipe) on the main flowpath at the pathway between Hale Place and Camden Street; and installing additional pits (and pipe sections) on Nelson Street, upstream of Sackville Street, that better target the overland flowpath. In addition to the above (or as an alternative), consider regrading Hale Place to redirect some/all of the surface water flow away from the residential properties immediately downstream of Hale Place.

FM09 Construct a ~50m bund along the top of the eastern bank of the Hamilton Road open concrete channel, at its downstream limit See Figure 9-1 and Figure 9-3 Additional details provided in Section 9.1.10

Under flood conditions, the open concrete channel paralleling Hamilton Road becomes overtopped at its downstream end, near the intersection of Barbara Street and Hamilton Road. This causes shallow flooding of Barbara Street properties that border the eastern (left) bank of the channel during the 1% AEP event.

To reduce floodwaters spilling out of the open concrete channel onto some bordering properties, construct a ~50m bund along the upper left bank at the downstream end of the channel. 1% AEP flood depths at these properties may be limited by constructing the bund to a minimum height of 9.65 m AHD.

FM10 Stormwater drainage improvements along Wilga Street, near Fairlight Avenue See Figure 9-1 and Figure 9-3 Additional details provided in Section 9.1.11

A secondary overland flowpath downstream of the railway flows south along Wilga Street (between its two intersections with Fairlight Avenue), before flowing across residential areas towards St Elmos Drain during the 5% AEP event and worse. This floodwater ponds in a local topographic depression in Wilga Street.

Improve the stormwater drainage networks on Wilga Street, between the two intersections with Fairlight Avenue, to reduce degree of overland flooding of the downstream residential areas. This option includes installation of addition pits/pipes along overland flowpath on the western side of the road.




FM11 Stormwater drainage improvements at The Crescent, east of Court Road See Figure 9-1 and Figure 9-3 Additional details provided in Section 9.1.12

Under flood conditions, water ponds along The Crescent, east of Court Road during the 1% AEP event. The limited stormwater drainage network on this section of road drains under the railway line into Prospect Creek. Backwater influence from Prospect Creek causes flooding of properties.

Improve the stormwater drainage network along The Crescent, east of Court Road, to improve drainage of ponded water.

FM12 Stormwater drainage improvements on Court Road See Figure 9-1 and Figure 9-3 Additional details provided in Section 9.1.13

Water becomes ponded on and around the intersection of Spencer to Alan Street and Court Road, where a local topographic depression occurs during the 5% AEP event and worse. A network of pits and pipes occur in these areas; however, the pit locations do not always align with the overland flowpaths.

Improve stormwater drainage networks around the intersection of Spencer to Alan Street and Court Road, to improve drainage of ponded water under flood conditions. This includes installation of new pits (and joining pipe sections) that target the Court Road flowpaths.

FM13 Flood Detention Basins See Figure 9-1 and Figure 9-3 Additional details provided in Section 9.1.14

Water ponds across a number of intersections along Barbara Street including Wrentmore Street, Kenyon Street and Harris Street. The stormwater network capacity is exceeded resulting in flowpaths across residential and commercial properties are activated during the 1% AEP event.

Remove overland flow from Barbara Street using 3 detention basins located at the corner of Wrentmore Street and Barbara Street, Kenyon Street and Barbara Street, and Harris Street and Barbara Street. It is anticipated that these would be below ground basins beneath existing carpark/vacant lots.

FM14 Regrading of Council Easement between Lyndon Street and Wilga Street See Figure 9-1 and Figure 9-3 Additional details provided in Section 9.1.15

Water passing through the Railway Parade rail culvert and down the Council easement is controlled by topographical high points.

To improve the conveyance of floodwater along the Council easement topographical high points should be removed. This should improve floodwater moving downstream away from the rail culvert towards St Elmos Drain during the 5% AEP event and greater.



Figure 9-1 Summary Map of Potential Mitigation Options: Fairfield CBD Overland Catchment



Figure 9-2 Potential Mitigation Options 1 to 6: Fairfield CBD Overland Catchment



Figure 9-3 Potential Mitigation Options 7 to 14: Fairfield CBD Overland Catchment



9.1.2 FM01 – Nelson/Ware Street FM01a - Nelsons Street Stormwater Drainage Improvements

Figure 9-4 FM01a Modelling Details A small cluster of business properties located immediately upstream of the Nelson Street and Ware Street intersection in Fairfield CBD are prone to overland flooding. Above floor flooding is simulated to occur in this area under design events ranging from the 20% AEP design event to PMF conditions. A single property is noted as flooding at the 20% AEP event. The approximate floor level above ground level at this property is only~0.1m, and accordingly may be impacted in shallow overland flow events as for the 20% AEP event. .

Flooding in this area occurs due to a local drainage issue caused by a high point in the Nelson Street road and a lack of stormwater drainage infrastructure in the immediate area. This causes shallow floodwaters to pool behind the Nelson Street/Ware Street intersection.

This option proposes to reduce the flood risk by adding pit and pipes to the existing stormwater network to drain the area prone to surface water ponding upstream of the Nelson Street and Water Street intersection (see Figure 9-4).

Modelling of this option results in a less than 0.01 m reduction in peak flood levels during the 20% AEP, 5% AEP and 1% AEP events upstream of the intersection, due to the capacity of the existing receiving stormwater network and the existing control of the high points across Nelson Street - see Figure C-1 and Figure C-16. There is no change to potential building inundation for this mitigation



option. As a result, this option is not recommended due to the minor potential reductions in peak flood levels and unchanged building inundation.

FM01b - Nelsons Street Road Regrading Works

Figure 9-5 FM01b Modelling Details An alternative measure to reduce the flood risk to business properties immediately upstream of the Nelson Street/Ware Street intersection involves road regrading works to remove the high point in Nelson Road (see Figure 9-5). This could allow surface water to flow freely downstream from the flood prone shopping arcade area that is currently exposed to shallow ponding. This option would see additional flows entering Ware Street to the immediate south of the Nelson Street and Ware Street.

Modelling of this option results in a maximum reduction in peak flood levels of 0.02 m, 0.04 m and 0.06m in the vicinity of the shopping arcade during the 1%, 5% and 20% AEP events respectively. The small reduction in peak flood level for the 20% AEP provides for a removal of the above floor flooding of the single property previously noted. However, the option does not change the flooding condition for the higher order events. Improving the flow efficiency across Ware Street provides for increases in peak flood levels downstream of the regrading works of the order of 0.03 m for the modelled events. Increases are generally contained within the road alignment, however, there are commercial properties through this area with close street frontage that may be impacted. There are slight changes to building inundation levels during both events as shown in Figure C-2 and Figure C-17.



9.1.3 FM02 -Barbara Street/Hamilton Road Intersection FM02a - Barbara Street / Hamilton Road Intersection Stormwater Drainage Improvements

Figure 9-6 FM02a Modelling Details Properties on and adjacent Barbara Street upstream of Hamilton Road, including Harris Street, have been identified as been at risk of inundation from overland flooding. Above floor inundation to several properties occurs from water ponding behind highpoints along Hamilton Road during flooding up to the 1% AEP event.

For events at 5% AEP and greater, the main flowpath downstream of Harris Street tracks along Harris Lane that parallels Barbara Street to the east. A high point across the intersection of Hamilton Road and the Harris Lane restricts surface flow southward causing floodwaters to pond upstream. The ponding floodwaters ultimately drain via Barbara Street. The ponding across Hamilton Road results in inundation of properties for the 1% AEP design event.

In order to reduce flood levels up to the 1% AEP design event, additional pits along Harris Lane to drain the area prone to surface water ponding have been investigated in this option (see Figure 9-6).

The modelled results for the proposed drainage mitigation option provide for negligible changes to peak flood levels (±0.01 m) upstream of Hamilton Road and no change to building inundation as shown in Figure C-3. Review of the modelled results indicate property inundation and flooding of this area during 1% AEP event or greater conditions are influence by a high point in Hamilton Road



controlling overland flows (refer to Option FM02b) and also backwater inundation from the Barbara Street Railway Culvert reaching capacity (refer to Option FM03a, FM03b for further details). .

FM02b - Barbara Street / Hamilton Road Intersection Road Regrading Works

Figure 9-7 FM02b Modelling Details A high point in Hamilton Road at the Barbara Street intersection may control overland flows and provide for higher flood level for upstream properties. Road regrading works provides an alternative measure to additional stormwater drainage pits investigated in option FM02a. This option involves regrading the southern end of Harris Lane and the length of Hamilton Road between this Harris Lane and Barbara Street to remove the highpoints that restrict free surface flow.

Figure 9-8 shows a longsection through Hamilton Road along the general flow path alignment along Barbara Street. The existing high point in Hamilton Road is evident from the ground level profile. The regrading option (noted as FM02b modelled surface) shos the intended removal of the control. The simulated water surface profiles for the existing and modelled mitigation option condition are shown for comparison.

This option provides peak flood level reductions of up to 0.05 m upstream of Hamilton Road during the 1% AEP event as shown in Figure 9-8 and Figure C-4. During the 5% AEP event, there were no changes to peak flood levels. The small reduction in peak flood level for the 1% AEP event does not change above floor flooding conditions for affected property.



Figure 9-8 FM02b Regrading Surface from North Side of Hamilton Road

The performance of the regrading option in reducing 1% AEP flood levels is somewhat limited by the backwater influence from the downstream railway culvert. This backwater influence is evident is Figure 9-8 with the elevated 1% AEP flood levels above the existing high point in Hamilton Road.

The full extent of the backwater influence from the railway culvert is further shown in Figure 9-9 and Figure 9-10. Figure 9-9 shows the alignment of a longsection profile extending from Harris Street to downstream of the railway embankment through the main overland flow path alignment.

The corresponding longsection is shown in Figure 9-10 providing a comparison of the ground levels with simulated 20% AEP, 5% AEP and 1% AEP peak design flood level profiles. Key intersections are noted for reference including the relative high points in Harris Street and Hamilton Road as discussed in Options FM01b and FM02b respectively.

Figure 9-10 shows the railway culvert has a significant backwater influence for the 1% AEP event extending to upstream of Hamilton Road. The culvert has limited influence on upstream conditions for the lower order 20% AEP and 5% AEP flood events.

Potential options for mitigation of the impact of the railway culvert and drainage at the end of Barbara Street are investigated as option FM03 below.



Figure 9-9 Barbara Street Long Section Map



Figure 9-10 Barbara Street Long Section Profile showing Design Flood Heights and Highlighting the Design Specific Flooding Controls

9.1.4 FM03 – Barbara Street Railway Culvert FM03a - Barbara Street Railway Culvert Upgrade Increasing Culvert Capacity by 50%

An upgrade in the Barbara Street railway culvert has been identified as potential flood mitigation option to reduce flood impacts to the Fairfield CBD area in, and around, Barbara Street. During the 1% AEP event, widespread backwater flooding occurs along Barbara Street between Railway Parade and Kenyon Street. This backwater flooding is caused by the railway culvert and the associated inlet reaching capacity as shown in Figure 9-10. Backwater flooding from the 1% AEP design event is simulated to cause above floor inundation to a number of business and residential properties in the adjoining area.

To mitigate backwater flooding caused by the Barbara Street railway culvert, the culvert was modelled with 50% extra capacity (additional 3.6 x 2.4 m culvert modelled). This resulted in negligible reductions (< 0.01 m) to peak water levels on the upstream side of the culvert, demonstrating the control of the inlet capacity rather than the culvert size itself over backwater flooding along Barbara Street during the 1% AEP event. During the 5% AEP event peak level reductions were < 0.01 m with no change to building inundation as shown in Figure C-5.

The hydrographs for the existing and modelled culvert are shown in Figure 9-11. From the hydrograph, it is evident that despite adding a third culvert to the existing culvert structure, the flow capacity is not increased. Therefore the system is limited by inlet capacity at this location.



Figure 9-11 FM03a Culvert Hydrograph

Figure 9-12 FM03a Modelling Details



FM03b - Barbara Street Railway Culvert Upgrade Doubling Culvert Inlet Capacity

As noted above, the backwater flooding arising from the Barbara Street railway culvert is attributed to the limited inlet capacity of the pits upstream of the culvert. This is demonstrated by the lack of reductions in peak flood levels afforded by increasing the railway culvert’s capacity (increasing it by 50%). As such, the inlet capacity of the most immediately upstream pit was doubled to allow for additional flow into the culvert itself, without increasing the capacity of the culvert (see Figure 9-14).

This option resulted in a modelled peak flood level reduction of 0.2 m on the upstream side of the culvert, extending upstream to Harris Street during the 1% AEP event. Downstream of the railway culvert peak flood levels increased by a maximum of 0.03 m as a result of additional flow through the railway culvert from the increased inlet capacity. During the 5% AEP event peak flood level reductions were up to 0.03 m in the area immediately upstream of the culvert. The inlet modification results in reductions to building inundation as shown in Figure C-6.

Figure 9-13 demonstrates the control of the inlet capacity on flow into the culvert. With the modelled upgrade, flow is doubled through the inlet allowing more water to flow through the rail culvert.

Figure 9-13 FM03b Culvert Inlet Hydrograph



Figure 9-14 FM03b Modelling Details

9.1.5 FM04 – Hamilton Road between Eustace Street & Sackville Street Stormwater Drainage Improvements Along Hamilton Road Between Eustace Street and Sackville Street

Overland flooding along the stretch of Hamilton Road between Eustace Street and Sackville Street forms a primary flowpath upstream of the Barbara Street railway culvert. The existing drainage capacity if of the order of 20% AEP design event, however, once exceeded the road may be subject to nuisance shallow flooding impacting on a number of properties. As stormwater drainage is only present along the northern side of Hamilton Road within this stretch, this option duplicates the drainage along the southern side of the road to provide additional stormwater capacity. The additional modelled stormwater drainage connects to the existing stormwater network on Sackville Street (see Figure 9-15).

Peak flood level reductions between Eustace Street and Sackville Street are generally up to 0.05m, 0.05m and 0.04 m for the modelled 20% AEP, 5% AEP and 1% AEP event. Figure C-7 and Figure C-18 shows reductions were primarily modelled in the stretch of Hamilton Road where drainage was added.



The velocity-depth product was reduced by up to 0.1 m2/s midway along Hamilton Road during the 1% and 5% AEP events.

The change in flood hazard is shown in Figure 9-16. As demonstrated, there is a reduction in flood hazard from majority H2 in the roadway to H1, reducing the hazard for small vehicles.

Figure 9-15 FM04 Modelling Details



Figure 9-16 FM04 Flood Hazard



9.1.6 FM05 – Hamilton Road between Sackville Street & Thomas Street Stormwater Drainage Improvements Along Hamilton Road Between Sackville Street and Thomas Street

Shallow overland flooding along the stretch of Hamilton Road between Sackville Street and Thomas Street impacts on several residential properties on the northern side of the road. Hamilton Road conveys main flowpaths that spill into adjoining properties via low points in the road. Furthermore, no stormwater drainage currently exists on the northern side of Hamilton Road.

To assist with draining shallow overland flooding along Hamilton Road, stormwater pits and pipes have been modelled along the northern side of the road connecting to the existing stormwater network on Thomas Street (see Figure 9-17).

Modelled reductions in peak flood levels were up to 0.02m for the 20% AEP event in some areas but typically less than 0.01m. Similarly, peak levels were only reduce by < 0.01 m for the 5% AEP event and 1% AEP events along Hamilton Road. Figure C-8 and Figure C-19 show the magnitude and extent of the flood level changes. Reductions in velocity-depth product were modelled along Hamilton Road and were up to 0.03 m2/s during both events. Due to the negligible change in peak flood levels and velocity-depth product along Hamilton Road with the additional drainage, no further action is recommended for this option.




9.1.7 FM06 – Railway Parade Improve Efficiency of Railway Culvert on Railway Parade (Near Austral Parade)

Several properties have been identified as subject to property inundation due to flooding upstream of the railway culvert on Railway Parade. Overland flooding along Railway Parade, located near Austral Parade, partly drains via a railway culvert with excess floodwater ponding immediately upstream of the culvert during the 20% AEP and greater events.

Flooding in this area is contributed to by local topographic constraints restricting flow into the culvert, particularly in the road verge adjacent to the culvert. Floodwater ponds in the intersection upstream of the railway culvert.

Figure 9-18 FM06 Modelling Details To address the restriction of surface water into the drain, the adjoining ground surface was regraded to enable floodwater to flow freely into the culvert (see Figure 9-18). Reductions in peak water levels of up to 0.13 m, 0.20 m and 0.24 m were modelled in the road corridor on the upstream of the culvert during the 1% AEP event, 5% AEP and 20% AEP event respectively (see Figure C-9 and Figure C-20). Further reductions of 0.07m to 0.09 m were modelled along Austral Parade to the north of the culvert during both events, as shown in Figure 9-19, however no changes to building inundation were modelled. The velocity-depth product was reduced within the road reserve by 0.07 m2/s during the 1% AEP and 5% AEP events, however there were localised increases of up to 0.03 m2/s during both events upstream of the culvert.



The change in flood hazard categories is shown in Figure 9-20. From this it is evident that the modelled option has resulted in a change of flood hazard category of H3 to H2 within the roadway, attributed to the reduction of flood depth.

Figure 9-19 FM06 Modelled Surface



Figure 9-20 FM06 Flood Hazard



9.1.8 FM07 – St Elmos Drain Improve Surface Drainage Connection with St Elmos Drain in the Vicinity of the Fairfield Recycled Water Plant

Overland flow draining south from the railway line and downstream of the Austral Parade railway culvert pools around topographical low points in the Fairfield Recycled Water Plant and around the adjacent electrical substation. Surface connection to St Elmos Drain is to the east of the Recycled Water Plant via a stormwater pit. Topographical high points surrounding the Recycled Water Plant prevent surface water flow from connecting to the stormwater pit to the east, causing inundation of the site.

To improve connectivity between surface flows around the Recycled Water Plant and St Elmos Drain, the grassy/open space between the plant and electrical substation were re-contoured for modelling, particularly along the south-east border of the plant (see Figure 8-17).

Modelled peak water level reductions were between 0.08 to 0.16 m around the substation and plant during the 1% AEP event, with greater reductions occurring around the south-eastern border of the plant where the surface connection to the stormwater pit was modified. During the 5% AEP event, peak level reductions were up to 0.20 m and were modelled adjacent to the plant and substation as shown in Figure C-10. Increases downstream of the plant at the existing stormwater grate were approximately 0.03 m for the 5% and 1% AEP events as a result of the improved surface water connection.




9.1.9 FM08 – Hale Place and Nelson Street FM08a & FM08b - Stormwater Drainage Improvements at Hale Place and Nelson Street, Redirecting Surface Flow

The northernmost overland flow upstream of the railway flows from Camden Street towards Barbara Street via Hale Place through a number of surrounding residential properties. The existing stormwater drainage pits on Hale Place are not optimally positioned on the main flowpath, causing the flowpath to bypass the stormwater network.

This option included stormwater network improvements via installing pit and pipes to better target the overland flowpath reducing the inundation of properties. This option also considered the potential for regarding Hale Place to redirect some surface flow away from residential properties immediately downstream of Hale Place.

This option was not modelled as the aforementioned stormwater network improvements exist, determined from a site inspection carried out on the 15/09/2017.

9.1.10 FM09 – Hamilton Road Drainage Channel Construction of Bund along the top of the Eastern Bank of the Hamilton Road Open Creek Channel at its Downstream Limit

During the 5% AEP event and greater, the open concrete channel overtops at its downstream end (near the intersection of Barbara Street and Hamilton Street), causing shallow flooding of properties along Barbara Street that border the eastern bank of the channel.

This option included constructing a bund along the existing fence line on the eastern bank of the channel to reduce floodwater spilling eastward into adjacent properties. To limit 5% AEP flooding for the bordering properties, a bund to a height of 9.55 m AHD was modelled. To limit 1% AEP flooding, a bund to a height of 9.65 m AHD was modelled (see Figure 8 16).

Peak flood level reductions of up to 0.20 m were modelled immediately east of the bund in neighbouring residential properties during the 1% AEP event. To the west of the bund, peak flood levels increased by a maximum of 0.06 m during the 1% AEP event as a result of the bund. Negligible changes occurred to peak flood levels during the 5% event as shown in Figure C-11.




9.1.11 FM10 – Wilga Street near Fairlight Avenue Stormwater Drainage Improvements Along Wilga Street, Near Fairlight Avenue

Overland flow travels along a section of Wilga Street downstream of the railway where no stormwater pits are located. This overland flow then tracks south-east across residential properties towards St Elmos Drain.

This option proposed to improve the stormwater network on Wilga Street between the two intersections with Fairlight Avenue by installing additional pits/pipes targeting the overland flowpath on the western side of the road.

Option 10 was considered unrealistic due to the existing grade along Wilga Street rendering additional stormwater drainage potentially ineffective. Furthermore, affected residential properties along Wilga Street are already elevated considerably above ground level (confirmed on site inspection). As such, no further action needs to be taken.

9.1.12 FM11 – The Crescent Stormwater Drainage Improvements at The Crescent, East of Court Road

During the 1% AEP event water ponds in The Crescent where limited pits/pipes exist. Existing stormwater drainage in The Crescent drains under the railway line into Prospect Creek. This option



proposed the installation of pits/pipes at the location of the ponding water to improve drainage along The Crescent.

No further action is recommended based on a site inspection undertaken. . The site inspection revealed that the current stormwater network is adequate and impacts arising from the modelled are likely to be an artefact of using direct rainfall.

9.1.13 FM12 – Court Road Stormwater Drainage Improvements on Court Road

Floodwater ponds along the intersection of Spencer Street, Alan Street and Court Road due to a local topographic depression in the road. It was noted that the stormwater network does not necessarily target overland flowpaths with installation of new pits/pipes recommended to target the stormwater drainage.

No further action is recommended based on a site inspection undertaken. The site inspection revealed that the current stormwater network is adequate and impacts arising from the modelled are likely to be an artefact of using direct rainfall.

9.1.14 FM13 – Barbara Street Flood Detention Basins

During flood events water ponds along the intersections of Wrentmore Street, Kenyon Street and Harris Street with Barbara Street. Flowpaths are activated outside of the road reserve across residential and commercial properties causing inundation of over 1 m at certain locations, likely due to the capacity of the existing stormwater network being exceeded.

To address this, flood detention basins have been modelled at the corners of Wrentmore Street and Barbara Street, Kenyon Street and Barbara Street, and Harris Street and Barbara Street. The three separate detention basins were linked to the existing stormwater network and to each other by a 1d drainage network to allow floodwater to move between the basins (see Figure 9-23).

During the 5% AEP event, reductions in peak flood levels of up to 0.20 m were modelled downstream of the railway culvert. During the 1% AEP event, reductions of 0.13 m were modelled downstream of the railway. Increases in peak flood levels (0.30 m) were modelled adjacent to the basins as a result of the basins overtopping. Across both of the events reductions were modelled downstream to St Elmos Drain due to the storage afforded by the basins (see Figure C-12). Despite the modelled reductions, it should be noted that the modelled configuration is idealistic and these reductions may be lessened by alternate configurations.




9.1.15 FM14 – Easement Between Lyndon Street and Wilga Street Regrading Council Easement Between Lyndon Street and Wilga Street

As noted in Section 9.1.4, an upgrade to the Barbara Street railway culvert has been identified as potential flood mitigation option to reduce flood impacts. Widespread backwater flooding occurs during the 1% AEP event, particularly along Barbara Street, which is caused by inadequate inlet capacity upstream of the culvert. In addition to the inlet capacity being exceeded, the easement downstream of the railway (between Lyndon Street and Wilga Street) also provides hydraulic control over floodwater from the culvert. Topographical high points along the easement reduce the conveyance of floodwater into St Elmos Drain downstream.

To mitigate this, the easement was modelled as being regraded (see Figure 9-24 and Figure 9-25), removing high points that provided control over flood levels. This option resulted in peak flood level reductions of up to 0.10 m during the 5% and 1% AEP events. There was no change to peak flood levels upstream of the rail culvert during both events. As such, this option in isolation is not feasible as it does not reduce flood levels upstream of the culvert during the modelled events due to backwater flooding as shown in Figure C-13.



Figure 9-24 FM14 Modelled Surface




9.1.16 Combinations of Flood Modification Options In addition to the options modelled above, two other options were modelled. These options considered a combination of selected options to determine the cumulative impact of their construction. Due to the backwater influence of the Barbara Street railway culvert and the resultant backwater flooding, a number of improvements were modelled to determine their success in combination, rather than in isolation.

FM03c - Barbara Street Railway Culvert Upgrade – Combination of Increasing Culvert Capacity & Culvert Inlet Capacity (FM03a + FM03b)

As the performance of the Barbara Street railway culvert is dependent on the inlet capacity of the pits upstream of the culvert, a combination of the above two options was modelled. This option was included as without increasing the inlet capacity of the railway culvert, additional flow would not be able to flow through the culvert itself. As such, increasing the culvert capacity in isolation of increasing the culvert’s inlet capacity produced negligible impacts on peak flood levels in the surrounding area.

Combining the two options resulted in a 0.16 m reduction in peak flood levels upstream of the railway culvert and a 0.03 m increase in peak flood levels downstream of the railway culvert during the 1% AEP event. During the 5% AEP event, peak flood level reductions were up to 0.03 m upstream of the culvert. There were no changes to existing above floor flooding during the modelled events (see Figure C-14).

Figure 9-26 FM03c Modelling Details



FM03d - Barbara Street Railway Culvert Upgrade – Combination of Increasing Culvert Capacity & Culvert Inlet Capacity + Regrading of Council Easement (FM03c + FM14)

An increase in peak flow through the railway associated with the culvert upgrade provides for increases in peak water levels downstream of the culvert through the overland flow easement between Lyndon Street and Wilga Street. To reduce the water level increases, a regrading of the easement has been considered to improve the conveyance of floodwater and offset potential impacts of the railway culvert upgrade (refer Figure 9-27).

The combination of the increases to the culvert inlet and culvert capacity with the regraded easement resulted in a 0.18 m reduction upstream of the culvert during the 1% AEP event. Downstream of the culvert, peak flood levels were reduced by 0.08 m along the northern section, with slight (0.02 m) increases modelled in the southern portion of the corridor along North Street. Reductions in property inundation (up to 0.15 m) were modelled upstream of the culvert as shown in Figure C-15 and Figure 9-28, however there were no changes to the number of buildings with above floor flooding.

During the 5% AEP event, peak flood level reductions up to 0.03 m were modelled immediately upstream of the culvert. Reductions of up to 0.13 m were modelled downstream of the culvert. No changes to building inundation were modelled during the 5% AEP event.

Figure 9-27 FM03d Modelling Details



Figure 9-28 FM03d Long Section Profile



9.2 Property Modification Measures The property modification measures considered have been summarised in Table 9-2 below and further detailed in the following sections.

Table 9-2 Potential Property Modification Options

Option # Option Name Option Description/Flood Issue Option Details

Property Modification Options

PM01 Development Controls

Planning controls will influence future development (and redevelopment) and therefore the benefits will accrue gradually over time. Planning controls to ensure development is consistent with the flood risk.

Overarching Council policies in place and previous review work undertaken for Canley Corridor FRSMP. Relevance to conditions in Fairfield CBD catchment will be reviewed. Key planning considerations may include: Flood planning levels S149 Certificate

information Building modifications to

accommodate overland flow

Basement car park entry levels

Rezoning due to flood risk (unlikely for Fairfield)

PM02 Voluntary Purchase

Voluntary purchase refers to the purchasing of homes and buildings located in areas subject to excessive hazards.

Occurs to buildings where the flood hazard is too high to be considered safe for occupancy and where mitigation measures are futile for reducing flood hazards.

PM03 Voluntary House Raising

Only limited existing properties have been identified with floor levels below the existing 1% AEP flood level. Note: no high-risk properties identified for Voluntary Purchase.

Voluntary house raising is aimed at reducing the flood damage to houses by raising the habitable floor level of individual buildings above an acceptable design standard (e.g. 1% AEP Flood Level +0.5m). The viability of a Govt subsidised scheme needs to be assessed against OEH guidelines and consider appropriate properties, damage reductions, uptake potential and landowner support.



Option # Option Name Option Description/Flood Issue Option Details

PM04 Flood Proofing

Flood proofing refers to the design and construction of buildings with appropriate water-resistant materials such that flood damage is minimised should the building be inundated. There are some existing properties impacted by floodwaters such that retrofitting may help reduce flood damage.

Property owners would be expected to undertake works at their own convenience. A public awareness campaign may help to inform the community of flood proofing measures, and could be supplemented with individual building inspections and property owner interviews. Encouragement to make a property more flood-resilient can be linked to the recommended Community Awareness Program.

PM05 Future Development Strategic planning can reduce the number of future and current properties impacted on by flooding. Restricting development in high risk areas can reduce flood damages.

Using flood mapping and exempt and complying developments strategic planning can prevent buildings being constructed in high risk flood areas such as floodways.

PM06 CBD Design Guide Best practice guidelines for mitigating flooding and to protect development from the impacts of flooding.

Using a set of guidelines for urban development can assist with preventing the construction of development in high flood risk areas and to protect new and old developments from flooding. Restricting certain developments or designs based on existing flood conditions will reduce future flood damages.

PM07 Fence Modification

Localised restriction to overland flows may exacerbate flooding conditions on individual properties.

Review locations of overland flowpaths where flow barriers are evident. Assess performance of removal of the flow restriction through fence modification measures such as raising or open construction type. Review options for landholder subsidies.

9.2.1 PM01 - Planning and Development Controls Land use planning and development controls are key mechanisms by which Council can manage flood-affected areas within the study area. Such mechanisms will influence future development (and redevelopment) and therefore the benefits will accrue gradually over time. Without



comprehensive floodplain planning, existing problems may be exacerbated and opportunities to reduce flood risks may be lost.

As discussed in Chapter 8, Council currently has a number of land use planning and development controls in place to manage flood-affected areas within the Fairfield LGA. The operation of the DCP has recently been reviewed by Molino Stewart (2015) as part of the Canley Corridor FRMS&P. Whilst the DCP review and recommendations refers specifically to the Canley Corridor and including a Canley Corridor development control matrix, the study acknowledges significant benefit could be obtained by using one development control matrix applicable to all overland flow catchments within the City, rather than creating separate matrices for individual overland flow catchments. Accordingly, some of the general overland flow recommendations can be considered for the Fairfield CBD catchment as summarised below:

Freeboard: It was recommended that the existing freeboard be reduced from 0.5 m to 0.3 m given the low overland flow depths, the fact that the 100 year ARI + 0.5 m FPL extended beyond the PMF and that modelled increases in rainfall associated with climate change did not significantly increase overland flow depths.

Delineation of very low flood risk precinct: This new flood risk precinct was defined as that part of the PMF floodplain above the 100 year ARI plus 0.3 m that was a low hazard to children and buildings. Most types of development would be permitted in this precinct without development controls, specifically controls associated with evacuation and structural stability. Sensitive uses and facilities, subdivisions and concessional development (for sensitive uses only) would however still be controlled.

FPL precedence: For areas affected by both mainstream and overland flooding, the DCP should be amended to state that the highest FPL will take precedence.

These recommendations and other minor modifications to general controls have not been formally adopted in Council DCP and are still under consideration. If generally considered appropriate for overland flow environments, these controls would be supported across the Fairfield CBD catchment. Additional details to be incorporated in the flood planning for the Fairfield CBD catchment are discussed below.

9.2.1.1 Flood Planning Levels The various flood risk mapping outputs updated for the current study are recommended to be adopted by Council and used in the development assessment process. Flood risk mapping outputs for the 1% AEP design event associated with overland flooding including design flood conditions (peak water level, depth and velocity), Flood Planning Area, hydraulic category (floodway, flood storage and flood fringe definition) and flood hazard mapping have been updated for Council use.

The Flood Planning Area (FPA) is the area of land below the Flood Planning Level (FPL) and thus subject to flood-related development controls. The FPA for the Fairfield CBD catchment is shown in Figure 9-29 including the relevant lots that may be subject to flood related development controls (flood control lots)..



In areas adjacent to Prospect Creek and Orphan School Creek which are exposed to both overland flooding and mainstream flooding, it is recommended the highest design 1% AEP flood level condition be adopted for planning purposes, regardless of the flooding mechanism.

9.2.1.2 Section 149 Planning Certificates Section 149(2) and 149(5) Certificates are an important mechanism for Council to communicate planning controls that apply to a parcel of land. Section 149(2) certificates play an important role of flagging the presence (or not) of mainstream flooding risk, while Section 149(5) certificates have the important function of detailing the type and level of flood risk (either mainstream and/or overland) and their associated flood planning levels for flood affected properties. The Section 149 (5) also provides a Flood Information Sheet identifying the type of flooding, design flood levels and existing flood risk.

To improve the acknowledgement and awareness of flood conditions on parcels of land, the Section 149 (5) may be updated to include additional flood information such as:

Site specific details such peak flood velocities/flow directions, depth mapping

Hazard and flood risk classifications

Mainstream and overland flow characterisations

The addition of these items is likely to streamline the DA process and assist with preventing changes in flow conditions across flood affected properties.

9.2.2 PM02 - Voluntary Purchase The primary objective of voluntary purchase (VP) is to reduce risks to personal safety by purchasing and removing houses located in areas subject to excessive hazard. A VP scheme is generally applicable only to areas where flood mitigation is impractical and the existing flood risk is unacceptable. VP may also be considered where purchase of a property enables other flood mitigation works (such as channel improvements or levee construction) to be implemented because the property will impede construction or may be adversely affected by the works with impacts not able to be offset. Guidelines for VP schemes has been prepared by NSW Office of Environment and Heritage (OEH, 2013a).

No properties have been identified as suitable for VP within the Fairfield CBD overland flow catchment. This reflects no property subject to excessive flood hazard considering the limited above floor flood inundation, and limited extent of floodway and high hazard flow areas as per Figure 4-4 and Figure 4-6.



Figure 9-29 Flood Planning Area



9.2.3 PM03 - Voluntary House Raising The NSW Office of Environment and Heritage (OEH, 2013b) has prepared a guideline for councils seeking funding from the NSW Government’s Floodplain Management Program for voluntary house raising (VHR) schemes. This guideline details the objectives, eligibility criteria, funding and implementation procedure for a VHR scheme that has been included in a council’s adopted Floodplain Risk Management Plan (FRMP) as part of a set of floodplain risk management measures.

Voluntary house raising is aimed at reducing the flood damage to houses by raising the habitable floor level of individual buildings above an acceptable design standard (e.g. 1% AEP Flood Level +0.5m). Voluntary house raising generally only provides a benefit in terms of reduced economic damages but does not eliminate the risk. Larger floods than the design flood (used to establish minimum floor level) will still cause building damages and the option does not address personal safety aspects. These risks are still present as the property and surrounds are subject to inundation.

Not all houses are suitable for raising. Houses of brick construction or slab on ground construction are generally not suitable for house raising due to expense and construction difficulty. Generally, this technique is limited to structures constructed on piers. Further, house raising for properties in the study area at risk of overland flooding may not be effective given:

houses that can be raised may be approaching the end of their useful life;

rebuilding rather than renovations may be more cost-effective and potentially the preferred option of landholders;

flood proofing existing property provides a cheaper alternative.

Only 4 existing residential properties have been identified with floor levels below the existing 1% AEP flood level. All of the properties are of brick construction. It is significant to note for all of these properties that the above floor flooding depth at the 1% AEP level is less than 0.1m. As such, given no properties of suitable construction, and indeed the relatively limited above floor flooding depths at the 1% AEP level, it is considered that a formal VHR scheme is not viable for this catchment.

As an alternative to a VHR scheme, Council may give consideration to establishing a subsidy scheme for flood proofing of properties affected at the 1% AEP level. Each property identified with above floor flooding potential at the 1% AEP event magnitude may be considered further to identify overall flood risk. The individual property details (construction type, age, configuration) will need to be considered in association with the on-site risk to determine suitability for other property modification measures. Further investigation may be undertaken to establish the level of landowner support for uptake potential on assistance with flood proofing.

This type of scheme may be suitable across other overland flow catchments within the Fairfield LGA. Accordingly, a broader investigation of the number of potential properties, potential costs, funding models etc may be undertaken as an LGA wide study.



9.2.4 PM04 - Flood Proofing Flood proofing refers to the design and construction of buildings with appropriate water-resistant materials such that flood damage is minimised should the building be inundated. Flood proofing is more effectively achieved during construction with appropriate selection of materials and design. Council’s Development Control Plan already includes requirements for flood proofing of buildings for new development. However, there are a number of non-structural options that can be retrofitted to existing property to help reduce flood damage including changes to joinery and fittings, floor coverings and electrical services.

These measures would be applicable for all new developments in this area and redevelopment of existing property. These measures are seen as an effective measure for much of the existing property constructed across natural overland flowpaths. Whereas the expense of house raising provides for minimal return in terms of loss reduction compared to the capital expense, flood proofing measures on an individual property scale can be effective in reducing flood damages for a significantly lower cost.

The extent of damage, cost of repairs, inconvenience and cleaning required following a flood event will depend on many factors including depth and velocity of water, period of inundation, amount of debris and silt in floodwater, and type of materials and construction. If floodwaters cannot be excluded from a property through other measures, flood proofing may provide a direct benefit in terms of reduced economic damages and social disruption.

Property owners would be expected to undertake works at their own convenience. A public awareness campaign may help to inform the community of flood proofing measures, and could be supplemented with individual building inspections and property owner interviews. Encouragement to make a property more flood-resilient can be linked to the recommended Community Awareness Program.

Direct consultation with landholders with potential for house raising/flood proofing must be undertaken initially to establish the level of support, with explanation of:

conditions of any subsidy offer (to be determined);

susceptibility of the house to flooding (following confirmation of floor levels);

anticipated benefits of raising the floor level or flood proofing house; and

potential funding arrangements.

9.2.5 PM05 - Future Development Strategic planning within the catchment can assist in reducing flood risk and planning for floodplain risk management. This pertains mostly to future developments in the catchment whereby controls can be implemented to protect increasing numbers of people residing in floodplain areas. The following sections identify development control measure where LGA wide development controls would have a significant benefit in managing potential impact of future development in overland flooding environs such as Fairfield CBD.



Exempt & Complying Development

Exempt development under Council’s DCP are minor developments not requiring approvals from Council, but may be subject to other legislative or approval requirements, such as sheds, carports, fences and decks and other low impact developments. Under the Fairfield LEP (2013), exempt developments must still have minimal environmental impacts and not be carried out on environmentally sensitive areas including State coastal waters or coastal lakes, wetlands, areas of high cultural significance, crown lands or areas of high biological value. Exempt development is not permitted on Flood Control Lots but some complying development is allowed on Flood Control Lots.

Complying developments do not require development consent under Council’s DCP and generally comprise uncomplicated developments that can be certified by external certifiers or fast-tracked through Council. These developments are generally more substantial than exempt developments. Like exempt development, complying developments must not be constructed on critical habitats, wilderness areas, environmental heritage areas, environmentally sensitive areas as outlined in State Environmental Planning Policy (Exempt and Complying Development Codes) 2008. Unlike exempt development, complying development cannot be undertaken in high risk flood areas or may require certification to ensure no changes to flood behaviour results from the development.

Complying development is permitted on Flood Control Lots where a Council or professional engineer can certify that development is not a:

flood storage area;

floodway area;

flow path;

high hazard area;

high risk area

The flood risk mapping developed as part of the current study is sufficient for Council to define flood control lots within the Fairfield CBD catchment.

On-Site Detention (OSD)

OSD provides storage of stormwater onsite to capture additional water generated onsite from increased impervious surfaces. OSD can reduce the volume and speed of floodwater downstream of the development and reduce impacts on the local drainage network. They are mostly used in instances where the existing stormwater drainage network is limited or where the flood risk downstream could be increased by the additional runoff generated by the development. Within the Fairfield Council LGA, OSD is required for all multi-unit residential development, boarding houses, residential flats, hostels, senior housing, car parks and shop-top housing in additional to industrial/commercial developments increasing impervious area according Council’s DCP.

Currently, Council’s Stormwater Management Policy (2017) requires impervious areas on residential sites to not exceed 70%, with any sites exceeding this value requiring OSD. This is considered adequate in reducing runoff from residential developments without OSD, but should continue to be policed by Council to ensure compliance by the community.



Given the existing highly urbanised nature of the Fairfield CBD catchment, and relatively slow redevelopment rates, it is unlikely that implementation of OSD would provide any meaningful reductions in catchment-wide flood risk in the coming decades. However, the incorporation of OSD (and other runoff storage measures) can offset the impact of future catchment development. Accordingly, an OSD policy as a standalone flood mitigation measure will not significantly impact on flood planning conditions in the Fairfield CBD catchment, but in principle, the measure is sound as a general tool in minimising changes to existing conditions as a result of redevelopment.

Continued application of the OSD policy for future development within the catchment is recommended in lieu of future policy review changes.

Flood Refuge / Shelter in Place

Council’s existing DCP provides the opportunity for shelter in place in some development scenarios. Whilst it is recognised that the safest place to be in a flash flood is well away from the affected area, evacuation may not be an effective strategy given inherent safety risks in some urban flood environments. The shelter in place option may be the most practical and safest response for building occupants during a flood. This recognises that for most locations in the catchment it is safer to stay within buildings rather than evacuate through more hazardous flood waters in the street. The ‘flashy’ nature of flooding and thereby limited warning/response time suggests that it will always be difficult to ensure everyone in the floodplain evacuates prior to flooding of evacuation routes.

Further, the flood conditions prevalent in the Fairfield CBD catchment are typically short duration and relatively low hazard, which suggests that isolation is likely to be limited to about a few hours in most events. Even where buildings are at risk of above floor flooding, there are no buildings identified to experience depths of more than 0.3m in a 1% AEP flood and only 15 would experience above floor flood depths of more than 1.2m in a PMF. These conditions are reflected in the flood hazard mapping included in Appendix A with respect to the standard flood hazard classifications as shown in Figure 4-5.

Almost all of the properties with greater than 1.2m overland flood depth at the PMF event are located within the backwater extent from the railway embankment. Significantly, for each of these properties the mainstream PMF levels as a result of Prospect Creek/Georges River exceed the local overland flooding condition. Accordingly, it is potentially the mainstream flooding condition driving the development controls in this instance.

Similar to the recommendations of the Canley Corridor FRMS, the Fairfield CBD Floodplain Risk Management Plan is recommended to incorporate:

Update of Local Flood Plan to acknowledge that evacuation is not a practical option for most buildings and provision for shelter in place is appropriate for new developments

Community education material to incorporate content on sheltering in place

Review DCP to ensure development controls continue permitting a shelter in place approach for properties affected by local overland flooding subject to appropriate risk assessment.



CBD Best Practice Design Guide

The Draft Fairfield City Centre Urban Design Study (Town Planning & Urban Design [TPG], 2017) was prepared for a number of key sites (over 2,500m2 in area) encompassing the Fairfield City Centre. The study identifies key urban design, built form and place making actions to improve the vitality and vibrancy of the Fairfield City Centre. The study acknowledges general flood risk and the requirement for ensuring developments comply with legislation and are constructed in a way that does not change flow conditions, flood risk, or endanger existing developments.

The CBD area represents a significant area of future development potential. A key outcome of the current study is the design flood risk mapping that will underpin flood risk management requirements of future development and implementation of appropriate development controls. Significantly, the CBD area is subject to both overland and mainstream flooding affectation from Prospect Creek. Accordingly, the compatibility of future development with both flooding mechanisms needs to be considered.

Councils existing development controls provide for a suitable framework for establishing development requirements to manage flood risk. But little guidance is provided how best to accommodate overland floodwaters or best practice in how to protect proposed development from overland flooding. Given the nature of potential flooding in the Fairfield CBD, redevelopment and intensification of development as proposed in the CBD area may give greater consideration to the following through the use of a CBD Best Practice Design Guide that will focus on the mitigation of flooding in the locality and protect development from the impact of flooding:

Underground car parking configurations – controls for basement parking entry levels are typically provided to a relevant standard of flood protection (e.g. 1% AEP plus nominal freeboard if required). The backwater influence of the railway embankment provides for flood levels to rise quickly up to significant depths at the PMF level. These risks should be considered in underground parking for future development. Potential design options include provision for vertical egress, automatic flood gates and flood warning mechanisms. These risks may also be incorporated into site specific flood emergency response plans.

Ground storey development – consideration of the flowpath and how it can be accommodated in design.

On-Site refuge - as noted above, the current study recommends future DCP review to ensure development controls continue permitting a shelter in place approach. Given the extent and severity of flood affectation up to the PMF level under both overland and mainstream flooding conditions, to facilitate development, many of the CBD properties may require these provisions. The nature of some properties may provide opportunity to enhance or provide more extensive shelter in place facilities in common building areas (e.g. increased floor area provisions above PMF level, back-up electricity/communications)

Flood Emergency Response Plans – future developments should be required to provide flood emergency response plans. In recognising the limited potential for a coordinated response from support agencies (e.g. SES, Emergency services) given the flash flood environment in the CBD catchment, these plans would aim to maximise potential for self-sufficiency of effective emergency response and a non-reliance on formal emergency services.



9.2.6 PM06 – Fencing The sensitive nature of overland flow environments to interventions from building and construction has warranted consideration of the impact of boundary fences on flood behaviour. Fencing and walls located in overland flowpaths is regulated by Chapter 11 of Council’s DCP. The DCP notes that it is unfavourable to have fences located in floodways but when unavoidable, fences should be constructed of flood-compatible materials and be open-type to not restrict flow from blockages.

The extent of overland floodways in the Fairfield CBD catchment at the 1% AEP flood magnitude was shown in Figure 4-4. The majority of the floodway network is generally confined to existing open channel reaches of the stormwater drainage network, roadways as major overland flow paths, established council drainage easements for overland flow. There is a relatively limited extent of overland floodway at the boundaries of private property. In considering the potential for fence modification to minimise flood impact, the properties identified in Figure 9-30 represent the locations where fence/property interact with main overland flow paths within the catchment. The figure shows the velocity-depth product of the 1% AEP flow through the locality, indicating the alignment of significant flowpaths. The extent of significant flow across private property boundaries is relatively limited to the Nelson Street/Wrentmore Street areas shown in Figure 9-30. Appendix A includes full catchment mapping where it can be seen the other major flow paths are typically confined to the road network and dedicated drainage easements.

Figure 9-30 Lots for Consideration of Fence Modification Voluntary fence modification is an incentive scheme whereby Council provides a subsidy to property owners to modify their fences to allow for the free flow of floodwaters. This minimises

VxD(m2/s)



backwater flooding of upstream properties and reduces the risk of damage to or catastrophic failure of the fence, potentially leading to rapid inundation of downstream properties.

Voluntary fence modification was recently considered by Molino Stewart (2015) in the upper part of the Canley Corridor catchment where a significant proportion of the overland flow passed through private property. Several issues with voluntary fence modification were highlighted and which have been summarised below:

Uptake: Consultation with the community suggested that a significant subsidy would need to be offered for people to participate in a voluntary fence modification scheme.

Administration: The establishment, promotion and implementation of a scheme would require the allocation of Council resources to the scheme and would pose an additional administrative demand.

Maintenance and enforcement: Maintenance of the modified fencing to ensure it functions as intended is a key concern, particularly if the property changed ownership. The establishment and enforcement of a positive covenant over the property and related to the fencing could be an issue.

Contracts and funding: The level of funding required and the funding support from the NSW Government were queried. The contractual relationship between Council, the property owner and the fencing contractor would also need to be clarified.

Voluntary fence modification is considered a viable option for the Fairfield CBD catchment, however additional work will be required to resolve the issues identified above.

9.3 Response Modification Measures A summary of the response modification measures is given in Table 9-3 below, with each option further detailed in the following sections.

Table 9-3 Potential Response Modification Options


Response Modification Options

EM01 Flood Warning

Given size of catchment and responsive nature of flooding, expect limited opportunity to enhance formal flood warning opportunities.

More direct flood warning opportunity may be provided for the road crossings subject to flood inundation. The installation of automatic flood warning signs would improve the response times in notifying the public of floodwaters across the road and provide more effective flood warning messages through display of flood depth or road closure notifications.




EM02 Emergency Response

It is important that the SES Local Flood Plan incorporates all relevant technical data and specific community vulnerabilities (including addresses of areas at highest risk) that have been determined through the Floodplain Risk Management process.

For some overland flooding situations, the SES’s role in flooding may be limited to assisting with recovery after the event. Occupants of premises within the flood prone areas should be encouraged to have private flood emergency response plans. Consideration to be also given to specific flood management plans for areas such as the shopping centres.

EM03 Community Awareness

Raising and maintaining flood awareness provides residents with an appreciation of the flood problem and what measures can be taken to reduce potential flood damage and to minimise personal risk during future floods

The community survey highlighted education and awareness as a key measure. The basic objectives of the community awareness program are to: • Make people aware they are living / working in a flood zone; • Provide information on receiving, understanding and reacting to flood warnings; and • Educate with regards to appropriate flood response actions - e.g. protecting property, vehicular and pedestrian access during flood time.

9.3.1 EM01 - Flood Warning There is no formal flood warning service for the Fairfield CBD overland catchment. However, there are a number of general warning services provided by the Bureau of Meteorology (BoM) including:

Severe Thunderstorm Warnings – typically provide 0.5 to 2 hours notice. These short-range forecasts are issued by the Bureau’s severe weather team and are based upon radar, data from field stations, reports from storm spotters as well as synoptic forecasts.

Severe Weather Warnings – for synoptic scale events that cause a range of hazards, including flooding. Examples of synoptic scale events are the deep low-pressure systems off the NSW coast that often result in significant flooding in eastern catchments.



Flood Watches – typically provide 24 to 48 hours notice. These are issued by the NSW Flood Warning Centre providing initial warnings of potential flooding based upon current catchment conditions and future rainfall predictions.

The CBD overland catchment is a highly urbanised and small catchment. For this reason, its response to flooding is rapid (often within an hour of heavy rainfall). This provides little opportunity to provide a warning of flooding based on rainfall that has already occurred; to disseminate that warning to the public; and for the public to take appropriate action to reduce their exposure to the flood threat.

Given the limited opportunity to provide any effective flood warning time, development of formal flood warning scheme for overland flooding is considered to be of little value.

There are currently no water level or rainfall gauges in the Fairfield CBD catchment. There are however a number of rainfall gauges within the local areas (i.e. <10km from the catchment boundary). A number of these nearby rainfall gauges feed into the publicly accessible BoM system which enables to community to access to flooding information specific to the Fairfield overland catchment3. However, considering the nature of overland flooding in the catchments, it is unlikely that the availability of the rainfall information will translate it into appropriate flood warning, dissemination and action by residents given time constraints.

More direct flood warning opportunity may be provided for the road crossings subject to flood inundation and hazardous conditions for vehicles, such as Barbara Street, Hamilton Road, Harris Street, Sackville Street and Nelson Street. The installation of automatic flood warning signs would improve the response times in notifying the public of floodwaters across the road and provide more effective flood warning messages through display of flood depth or road closure notifications. Automated warning signs can provide additional benefit through:

warning sign activation based on water level sensor;

depth of flooding indicator based on water level sensor;

communication options such as SMS alert of activation / change of state.

Figure 9-31 shows a sample warning sign which could be installed. As noted, a configuration that included a water level sensor can provide for activation of the sign based on a floodwater depth and corresponding flood depth warning messages.

3 Nearby rainfall gauges accessible via BoM include: Merryland West, Woodville Golf Club Guildford, Bankstown, Liverpool (Scrivener Street), Fairfield City Farm.



Figure 9-31 Example of Automatic Flood Warning Signs The challenge for the Fairfield CBD catchment is that major road affectation only becomes a significant issue for events of 1% AEP and above. Accordingly, there is considered little merit in these type of warning devices. Flood depth markers may be considered an alternative at locations where road inundation depths are significant. These locations include Sackville Street (between Joyce Street and Hamilton Road), Barbara Street (in area influence by railway culvert backwater), North Street (at main channel alignment).

9.3.2 EM02 - Emergency Response The State Emergency Service (SES) has formal responsibility for emergency management operations in response to flooding. Other organisations normally provide assistance, including the Bureau of Meteorology, Council, police, fire brigade, ambulance and community groups. Emergency management operations are usually outlined in a Local Flood Plan (LFP).

Information contained in the LFP is largely derived via local knowledge, historical record and completed flood studies. The SES follows the LFP, using information from Flood Intelligence and BoM’s predictions, to respond in actual flood events.

It is important that the SES Plan incorporates all relevant technical data and specific community vulnerabilities (including addresses of areas at highest risk) that have been determined through the Floodplain Risk Management process. Provision of this data is particularly important with regard to those areas with properties susceptible to above floor flooding or where key transport routes are subject to closure. The key improvements to emergency response considered in the current study is update local flood intelligence data with the revised understanding of catchment flooding conditions as per the design flood modelling assessment.

For rapid onset of flooding such as may be experienced in the Fairfield CBD catchment, it would not be realistic to expect the SES to be able to undertake much in the way of emergency response for several reasons:



the SES is principally a volunteer organisation and the time required to mobilise personnel could exceed the warning time available;

a major flood event is likely to coincide with major flooding in other catchments within the greater Georges River catchment and Sydney Region, further stretching already limited emergency response resources; and

there is generally insufficient time to undertake tasks such as sandbagging or evacuation to reduce impacts on property or people.

For some overland flooding situations, the SES’s role in flooding may be limited to assisting with recovery after the event. That is not to say that the SES Flood Emergency Plan will not in some measure mitigate the impacts of flooding. What it does mean is that they cannot be relied upon alone to provide an appropriate level of protection, particularly the protection of lives. In the rapid onset of a flood, individuals and groups of people must essentially take appropriate actions to protect themselves.

A summary of the emergency response issues to be incorporated in the study include:

Update of local flood intelligence – in consultation with SES utilising updated flood model information and cross linkage to monitoring sites and local property databases:

○ design flood mapping

○ property database and inundation statistics

○ key levels at monitoring locations (event references - design and historical)

○ evacuation arrangements

○ recovery Plans

Road closures

○ clear roles of responsibility during flood

○ warning issue and dissemination

○ activation of road closures and corresponding operational safety measures

Personal Flood Action Plans – in recognition of the potential for limited external support and requirement for self-help.

9.3.3 EM03 - Community Awareness Raising and maintaining flood awareness provides residents with an appreciation of the flood problem and what measures can be taken to reduce potential flood damage and to minimise personal risk during future floods.

The basic objectives of the community awareness program are to:

make people aware they are living / working in a flood zone;

provide information on receiving, understanding and reacting to flood warnings; and



educate in regard to appropriate flood response actions - e.g. protecting property, vehicular and pedestrian access during flood time.

Community awareness is an on-going process to overcome the inherent complacency between events. There are numerous mechanisms to inform the community, such as:

flood mapping availability (Council website) - Consolidation of the recent flood risk mapping, flood data and flood damages database prepared during the floodplain risk management study into Council’s computer based GIS system. This will provide Council with valuable flood information that can be easily retrieved, and which will form the basis of information that can be supplied to the public when requests are made, or on a periodic basis.

Section 149 certificates or flood certificates or on-line flood information advice- Consideration could be given to providing information on the flood risk and the flood levels that apply to a particular property on a special flood certificate. These certificates could be appended to the Section 149(5) certificates; provided whenever flood information is requested for a property; or provided on a regular basis to all residents in the study area.

flood information page on community websites (e.g. – this can include links to BoM rainfall and flood warning pages, a how to guide in understanding and reacting to flood warnings. This may be extended to other media including community newsletters/publications with Council providing regular input regarding flood awareness/preparedness, commemoration of historic events etc.

installation of flood depth markers at road crossings affected by flooding.

undertake a formal flood education, awareness and resilience program. Education is required to build a flood-resilient community who is prepared for flooding and able to respond to and recover from actual flooding. There are few planning or administrative barriers that would delay the development and implementation of a community education plan. Education and flood awareness should be a key role for combat agencies such as the SES, with Council having a key supporting role to play in assisting SES with the technical elements of flood characteristics of overland flooding in the catchments. Flood education should be prepared for the entire community with more specific content for residents and businesses at risk of flooding. Assistance in the preparation of flood planning documents should be available, particularly to non-English speaking background populations. Programs should be available online and face-to-face and be rolled out in multiple languages.

Given the relatively low incidence of flood affectation to existing property with on the Fairfield CBD catchment, an extensive community education and awareness program may be of little value. A more targeted approach could be employed focusing on the identified flooding hot-spot areas, e.g. residential and business properties in and around Barbara Street.

9.4 Mainstream Flood Management Measures The above description of potential flood management options target overland flooding risks to the Fairfield CBD overland catchment. Mainstream flooding risks to the downstream section of the overland flooding catchment are also present and particularly adjacent Prospect Creek and Orphan School Creek (including sections of Orchard Road and Riverview Road) Specific management



actions to address mainstream flood risks to this area are detailed in the Prospect Creek Floodplain Management Study and Plan by Bewsher (2010). These options include:

voluntary house raising program

voluntary house purchase scheme

road raising (Orchard Road – 120m)

stream clearing measures (Prospect Creek from Fairfield Street to Burns Creek)

basin safety review (with respect to mainstream flooding events more extreme than 1%AEP)

flood warning measures for Lower Prospect Creek

flood risk management DCP provisions for Prospect Creek

These mainstream options are supported but not expanded on further in the current study. The reader is directed to the Prospect Creek floodplain management study and plan by Bewsher (2010) for additional details on the above listed mainstream flooding options.

9.5 Analysis of Potential Management Options A simple matrix has been developed to assess the positive and negative benefits and costs of the recommended actions. The criteria are based on a “traffic light” colour system to clearly display if an aspect of an option should be cause to “stop” and reconsider, “slow” to proceed with caution or “go” with few trade-offs expected.

The aim of the rapid analysis is to provide a straightforward overview of the various actions applicable for the Fairfield CBD catchment, presenting quickly and clearly to community the benefits and trade-offs of a particular action, to assist in the prioritising and ordering of works within the immediate, medium and longer terms.

The criteria used for the rapid analysis is described below and summarised in Table 9-4.

Performance

The performance criterion considers how well the action would actually address the risks it is specifically targeting. The performance criterion also factors whether the action provides a long-term solution, or is just a short-term fix.

The criterion for Performance is based on a scale from high to low, where high performance represents effectiveness of the action in addressing flood risks, and low performance represents low performance or uncertainty in the outcomes.

Practicality / Technical Feasibility

The practicality criterion considers how easy and practical the action will be to implement. If the action can be considered standard process for Council or other agencies with minimal delays and hurdles, then the practicality would be high. If there are some barriers or delays to the option being implemented, then the practicality would be lower. With reducing practicality, it is expected that the effort (and costs) required to implement the action would increase.



Community Acceptance

The community acceptance criterion aims to reflect the general support for the action by the community as a whole. It is recognised that some actions may have a small section of the community that is most affected, however, it is the expected opinions of community at large that have been captured by this criterion.

Environmental Impacts

The environmental criterion aims to reflect the scale of potential impacts on the environment. Measures with major impacts are likely to trigger a requirement for formal environmental assessments (REF or EIS). Some measures may have a positive environmental effect (e.g. pollution prevention, habitat creation)

Costs / Resource Needs

Floodplain Risk Management actions can be inherently costly, especially when dealing with engineered works or property modifications. Planning controls are the exception to this, although these can still require significant effort from Council and others.

The Costs / Resource Needs criterion represents a rating wherein a High Rating reflects the lowest costs, while a Low Rating reflects the highest costs. This has been adopted for consistency with the other criteria.

The results of the Rapid Analysis are presented in Table 9-5. This table also gives a Total Score for each action. The score is calculated based on the following points system:

all HIGH (go) criteria have a score of +1

all MEDIUM (slow) criteria have a score of 0

all LOW (stop and reassess) criteria have a score of -1.

The performance criteria for the structural options (i.e. FM01 to FM14) has been given a double weighting (i.e. -2 for low and +2 for high). This is to reinforce the effectiveness of the measure in tangible flood risk reduction in the score weightings. This helps to avoid a relatively high overall score for an option that has little or no benefit in flood risk reduction with no other major constraints in implementation.

Table 9-4 Rapid Analysis Assessment Criteria

LOW (STOP

& reassess)

MEDIUM (SLOW)

HIGH (GO)

Performance Action is not particularly effective over the short

or longer terms

Action provides only a short-term fix, or is only partly effective over the

long term

Action provides an effective long-term solution to the risks

identified



Practicality

Acton would be difficult to implement through existing constraints,

approvals required etc. Would be very demanding to

successfully implement

Action would have some hurdles for

implementation, which may take longer and

demand more effort to overcome.

Action is straightforward to implement with few

barriers or uncertainties

Community Acceptability

Unlikely to be acceptable to the

majority of the community and

politically unpalatable. Significant championing required by Council and

State.

Would be palatable to some, not to others.

Briefing by Councillors, GM and community education required.

Is very politically palatable, acceptable to

community. Minimal education required

Environmental Impacts

Likely to have significant adverse environmental impacts unable to be effectively managed

Likely to manageable environmental impacts

through appropriate assessment and

planning

No significant environmental impact

identified. Environmental /

ecological benefit through measure implementation

Costs / Resources

Very Expensive (more than $1,000,000) and/or

very high (unmanageable)

resource demands on authorities

Moderately expensive (e.g. $100,000 -

$1,000,000) and/or high resource demands on

authorities

Manageable costs (< $100,000) and

manageable resource demands on authorities

The scoring in the rapid analysis provides some indication on the recommended prioritisation of the recommended measures. The higher scoring options typically have few barriers to implementation whilst providing effective floodplain risk management benefit.

Table 9-5 Assessment of Management Options

Performance

Perf

orm

ance

Prac

tical

ity

Com

mun

ity

Acc

epta

bilit

y

Envi

ronm

enta

l

Cos

ts/

Res

ourc

es

Tota

l Sco

re

Structural Measures

FM01a Nelsons Street stormwater drainage LOW MEDIUM HIGH HIGH HIGH 1

FM01b Nelsons Street road regrading works LOW MEDIUM HIGH HIGH HIGH 1



Performance

Perf

orm

ance

Prac

tical

ity

Com

mun

ity

Acc

epta

bilit

y

Envi

ronm

enta

l

Cos

ts/

Res

ourc

es

Tota

l Sco

re

FM02a Hamilton Road stormwater drainage LOW MEDIUM HIGH HIGH HIGH 1

FM02b Hamilton Road - road regrading works LOW MEDIUM HIGH HIGH HIGH 1

FM03a Barbara Street culvert upgrade LOW LOW HIGH HIGH MEDIUM -1

FM03b Barbara Street culvert inlet upgrade MEDIUM MEDIUM HIGH HIGH HIGH 3

FM03c Barbara Street culvert and culvert inlet upgrade

MEDIUM LOW HIGH HIGH MEDIUM 1

FM03d Barbara Street culvert and culvert inlet upgrade & regrading

MEDIUM LOW HIGH HIGH MEDIUM 1

FM04 Hamilton Road stormwater drainage LOW MEDIUM HIGH HIGH HIGH 1

FM05 Hamilton Road stormwater drainage LOW MEDIUM HIGH HIGH HIGH 1

FM06 Railway Parade culvert regrading LOW HIGH HIGH HIGH HIGH 2

FM07 Surface connection to St Elmos Drain LOW MEDIUM HIGH HIGH HIGH 1

FM09 Bund at Hamilton Road channel MEDIUM MEDIUM MEDIUM HIGH HIGH 2

FM13 Flood detention basins MEDIUM LOW MEDIUM HIGH MEDIUM 0

FM14 Regrading Council easement LOW MEDIUM HIGH HIGH HIGH 1

Property Modification



Performance

Perf

orm

ance

Prac

tical

ity

Com

mun

ity

Acc

epta

bilit

y

Envi

ronm

enta

l

Cos

ts/

Res

ourc

es

Tota

l Sco

re

Investigate House Raising Program MEDIUM HIGH MEDIUM HIGH HIGH 3

Flood proofing of individual properties MEDIUM HIGH MEDIUM HIGH HIGH 3

Planning and Development Controls

Update Hydraulic Category Mapping HIGH HIGH HIGH HIGH HIGH 5

Adopt Flood Planning Area Mapping HIGH HIGH MEDIUM HIGH HIGH 4

Flood Warning and Emergency Response

Install Automated Flood Warning Signs LOW MED HIGH HIGH HIGH 2

Update to Local Flood Plan and Emergency Response HIGH HIGH HIGH HIGH HIGH 5

Ongoing Community Education and Awareness MED HIGH HIGH HIGH HIGH 5

Of note in the table are the lowest scoring options being most of the structural options. This is reflective of the limited flood risk reduction afforded by the options, providing for a “low” performance score. Many of these options also have been scored “medium” for practicality given that works in most locations are expected to provide significant disruption to the community. Further detail justifying the above analysis is given in Table 9-6 below.



Table 9-6 Structural Flood Modification Option Validation

Performance Practicality Community Acceptance Environmental Costs/Resources

FM01a – Nelson Street Stormwater Drainage

< 0.01 m reduction in peak flood levels (20%, 5% and 1% AEP event)

Nelson Street is a main thoroughfare with works likely to cause significant disruption to CBD traffic and businesses

Uncontentious works unlikely to adversely impact the community

Highly unlikely to adversely impact on the surrounding environment

Likely to incur low cost due to limited pit/pipe installation

FM01b – Nelson Street Regrading Works

Up to 0.06, 0.04m 0.02 m reduction in peak flood levels during the 20% AEP, 5% and 1% AEP event respectively.

Nelson Street is a main thoroughfare with works likely to cause significant disruption to CBD traffic and businesses



Likely to incur low cost due to extent of regrading works

FM02a – Hamilton Road Stormwater Drainage

< 0.01 m reduction in peak flood levels (5% and 1% AEP event)

Hamilton Road is a main thoroughfare with works likely to cause significant disruption to CBD traffic and businesses




FM02b – Hamilton Road Regrading Works

Up to 0.05 m reduction in peak flood levels (1% AEP event) with no change during the 5% AEP event.

Hamilton Road is a main thoroughfare with works likely to cause significant disruption to CBD traffic and businesses



Likely to incur low cost due to extent of regrading works

FM03a – Barbara Street Culvert Upgrade

< 0.01 m reduction in peak flood levels (5% and 1% AEP event)

The Cabramatta-Granville Railway is a main passenger line with works likely to cause significant disruption to the railway and Barbara Street



Likely to incur significant cost due to excavation and replacement of railway




FM03b – Barbara Street Culvert Inlet Upgrade

Up to 0.03 m and 0.20 m reduction in peak flood levels for the 5% and 1% AEP events respectively

The Barbara Street inlets are located at the edge of the roadway and their replacement is unlikely to cause significant disruption



Likely to incur medium cost due to the nature of the inlet upgrade and location outside of the roadway

FM03c – Barbara Street Culvert and Culvert Inlet Upgrade

Up to 0.03 m and 0.16 m reduction in peak flood levels for the 5% and 1% AEP events respectively

The Cabramatta-Granville Railway is a main passenger line with works likely to cause significant disruption to transportation



Likely to incur medium cost due to the location of the inlet outside of the roadway combined with the excavation and replacement of the railway

FM03d – Barbara Street Culvert and Culvert Inlet Upgrade & Regrading

Up to 0.03 m and 0.18 m reduction in peak flood levels for the 5% and 1% AEP events respectively upstream of the culvert

The Cabramatta-Granville Railway is a main passenger line with works likely to cause significant disruption to transportation



Likely to incur medium cost due to the location of the inlet outside of the roadway combined with the excavation and replacement of the railway and regrading of Council’s easement

FM04 – Hamilton Road Stormwater Drainage

Up to 0.04 - 0.05m reduction in peak flood for 20% AEP, 5% AEP and 1% AEP events. Velocity-depth product was reduced during the 1% & 5% AEP events with a decrease in flood hazard for small cars

Hamilton Road is a main road with works likely to cause significant disruption to traffic and residents




FM05 – Hamilton Road Stormwater Drainage

< 0.01 m reduction in peak flood levels and up to 0.03 m2/s reduction in velocity-depth product during the 20% AEP, 5% AEP and 1% AEP events

Hamilton Road is a main road with works likely to cause significant disruption to traffic and residents







FM06 – Railway Parade Culvert Regrading

Up to 0.13 m and 0.20 m reduction in peak flood levels during the 1% AEP and 5% AEP events with a reduction in flood hazard within the roadway

Low level of disruption likely to occur as regrading is isolated to the road verge



Likely to incur low cost due to limited extent of regrading works

FM07 – Surface Connection to St Elmos Drain

Up to 0.20 m and 0.16 m reduction in peak flood levels during the 5% AEP and 1% AEP events

Medium level of practicality associated with disruptions to the Plant and complexity of regrading



Likely to incur low cost due to limited extent of regrading works

FM09 – Bund at Hamilton Road Channel

Up to 0.20 m reduction in peak flood levels during the 1% AEP event with associated potential increases to adjacent properties

Medium practicality due to ease of installation of bund, however may cause disruptions to adjacent properties

Unlikely to be accepted by all the adjacent properties that may experience adverse impacts


Likely to incur low cost due to limited extent of bund

FM13 – Flood Detention Basins

Up to 0.20 m and 0.13 m reduction in peak flood levels during the 5% AEP and 1% AEP events

Major disruptions to existing carparking areas during installation

Unlikely to be accepted by entire community due to disruptions and changes to parking conditions. Potential increases to adjacent properties


Medium cost of installation associated with excavation and installation of underground basins as areas currently used as carparks

FM14 – Regrading Council Easement

Up to 0.10 m reduction in peak flood levels during the 1% & 5% AEP events

Regrading of easement likely to cause little disruption, however large extent of regrading to occur adjacent to properties



Likely to incur low cost due to simplicity of regrading works to occur



9.5.1 Summary of Short Listed Options Community feedback on the options assessment will be an intrinsic component of formulating the recommended Floodplain Risk Management Plan. The public exhibition of the Draft Floodplain Risk Management Study provides the opportunity for community feedback on the options assessed.

On the basis of the options assessment above, a preferred floodplain risk management strategy, that is both practical and effective, would include the following options:

Structural Options

FM03d - Barbara Street culvert capacity/inlet upgrade coupled with regrading of the Council easement downstream of the railway – noted for feasibility investigation

Property Modification

PM03 – Investigate Flood proofing subsidy as alternative to House Raising Program

PM04 - Flood proofing of individual properties

PM05 - CBD Best Practice Design Guide

PM06 - Investigation of fence modification

Planning and Development Controls

PM01 - Update of Flood Risk Mapping

PM05 - Consideration of DCP changes from Canley Corridor study, with particular reference to:

o Overland flow freeboard of 300mm

o Provisions for shelter in place

Flood Warning and Emergency Response

EM02 - Update relevant local flood plan and emergency response plan

EM03 - Ongoing Community Education and Awareness

Fairfield CBD Floodplain Risk Management Study and Plan 132 Floodplain Risk Management Plan


10 Floodplain Risk Management Plan The Fairfield CBD Flood Risk Management Plan (the FRM Plan) has been developed to direct and co-ordinate the future management of flood prone lands within the Fairfield CBD Catchment. The FRM Plan sets out actions and initiatives that are to be pursued by Council, agencies and the community in order to adequately address the risks posed by flooding. Development of the FRM Plan has been guided by the NSW Government’s Floodplain Development Manual (2005).

The FRM Plan only considers overland flooding within the catchment. Part of the catchment is affected by mainstream flooding conditions of Prospect Creek. The management of mainstream flooding issues are addressed in the Prospect Creek Floodplain Risk Management Study & Plan.

The outcomes of the Study provide the basis for this FRM Plan, containing an appropriate mix of management measures and strategies, to help direct and coordinate the responsibilities of Government and the community in undertaking immediate and future flood management works and initiatives. The floodplain management measures and strategies that are recommended for inclusion in the FRM Plan are summarised below.

10.1 Recommended Measures Section 9 of the Floodplain Risk Management Study identified a number of potential flood management options for the Fairfield CBD catchment, including potential structural options, planning measures, and flood warning and responses measures. The options were assessed against a number of criteria (refer Table 9-5) to identify an appropriate mix of recommended measures to assist in prioritising and ordering of works within the immediate, medium and longer terms.

10.1.1 Flood Modification Measures

10.1.1.1 FM03d - Barbara Street Culvert Inlet Upgrades and Fairlight Ave Easement Regrading Inlet and culvert upgrades have been considered for the trunk drainage line along Barbara Street that discharges under the railway line. Backwater flooding occurs along Barbara Street between Railway Parade and Kenyon Street caused by the railway culvert and the associated inlet reaching capacity.

Preliminary assessment of inlet capacity duplication provides for some reductions in peak flood levels. These reductions do not reduce the incidence of above floor flooding for existing properties; however, there are associated benefits in reduced public risk, improved flood access and reduction in traffic disruption. A greater amplification of the existing infrastructure may realise increased flood level reductions and greater net benefits. However, being associated with the crossing of a major rail infrastructure there is likely to be considerable design and construction constraints. Accordingly, it is proposed that a more detailed feasibility assessment be undertaken on the potential for upgrades to the culvert system. The regrading of the Fairlight Avenue easement is required in order to reduce the potential flood impact of higher discharges downstream of the rail embankment due to the culvert system upgrades.



The feasibility study should also incorporate potential embankment modifications to reduce the PMF flood risk. Much of the CBD area upstream of the railway embankment is directly affected by the backwater influence of the railway embankment prior to overtopping. In actual events, parts of the embankment may fail thereby reducing peak flood levels. The option feasibility study may consider higher level culvert/flow provisions for PMF flows.

Given the complexity and variability of construction works associated with this option (major rail infrastructure impact), preliminary cost estimates may be subject to significant variation. An initial preliminary cost estimate of $1.4M is provided. Similarly, flood reduction benefits would be highly dependent on the ultimate solutions, noting however, most of the reductions in above floor flooding would only be realised for events in excess of the 1% AEP event. The feasibility study would incorporate the full cost-benefit analysis subject to confirmation of option potential.

Estimated Cost – $50K (Feasibility) / $1.4M (design and construction) Responsibility – Council / Transport for NSW Priority – Medium

10.1.2 Property Modification Measures

10.1.2.1 Planning and Development Controls Land use planning and development controls are key mechanisms by which Council can manage flood-affected areas within the study area. Such mechanisms will influence future development (and redevelopment) and therefore the benefits will accrue gradually over time. Key recommendations for changes in planning controls, specifically to address overland flooding mechanisms, have been incorporated in the Canley Corridor Floodplain Risk Management Plan. These recommendations are also considered appropriate for the Fairfield CBD catchment. Accordingly, the Fairfield CBD FRM Plan endorses these recommendations and include a recommendation for further Council review/consideration.

Various flood risk mapping outputs updated for the current study are recommended to be adopted by Council and used in the development assessment process.

Council adoption of 1% AEP flood condition and application of FPLs on the basis of flood modelling results developed in the current flood study.

Council adoption of the flood risk mapping associated with the current flood study 1% AEP flood event incorporating design flood conditions, Flood Planning Area, hydraulic category (floodway, flood storage and flood fringe definition) and flood hazard. These maps are to effectively form a referenced component of the LEP and DCP.

Estimated Cost – low (staff costs) Responsibility – Council Priority – High

10.1.2.2 Investigation of Flood Proofing Subsidy Alternative to Voluntary House Raising Only limited existing properties have been identified as being subject to above floor inundation at the 1% AEP flood level. Additionally, house raising in the study area may not be effective given:

House type construction (e.g. slab on ground) not suitable for raising;

Houses that can be raised may be approaching the end of their useful life;



Rebuilding rather than renovations may be more cost-effective and potentially the preferred option of landholders;

Flood proofing existing property provides a cheaper alternative development.

As an alternative to a VHR scheme, Council may give consideration to establishing a subsidy scheme for flood proofing of properties affected by above floor flooding at the 1% AEP level. The individual property details (construction type, age, configuration) will need to be considered in association with the on-site risk to determine suitability for other property modification measures.

This type of scheme may be suitable across other overland flow catchments within the Fairfield LGA. Accordingly, a broader investigation of the number of potential properties, potential costs, funding models etc may be undertaken as an LGA wide study. The viability of a scheme is dependent on establishing a suitable funding model and the uptake of the scheme given that it is on a voluntary basis. Further investigation may be undertaken to establish the level of landowner support and therefore uptake potential, to assess the merit of including a flood proofing subsidy scheme in future revisions of the Floodplain Risk Management Plan.

Estimated Cost – low (~$30,000) Responsibility – Council Priority – Medium

10.1.2.3 Flood Proofing Flood proofing refers to the design and construction of buildings with appropriate materials (i.e. material able to withstand inundation, debris and buoyancy forces) so that damage to both the building and its contents is minimised should the building be inundated during a flood. Flood proofing can be undertaken for new buildings or be retrofitted to existing buildings. Generally these works would be undertaken on a property by property basis at no cost to Council.

Council’s Development Control Plan already includes requirements for the use of flood compatible building components for new development in the floodplain. However, there are a number of non-structural options that can be retrofit to existing property to help reduce flood damage including changes to joinery and fittings, floor coverings and electrical services.

A public awareness campaign may help to inform the community of flood proofing measures, and could be supplemented with individual building inspections and property owner interviews. Encouragement to make a property more flood-resilient can be linked to the recommended Community Awareness Program.

Estimated Cost – low ($20,000 per property) Responsibility – Council/Landowner Priority – Medium

10.1.2.4 Fairfield CBD Best Practice Design Guide Councils existing development controls provide for a suitable framework for establishing development requirements to manage flood risk. But little guidance is provided how best to accommodate overland floodwaters or best practice in how to protect proposed development from overland flooding. Given the nature of potential flooding in the Fairfield CBD, redevelopment and intensification of development as proposed in the CBD area may give greater consideration to the following through the use of a CBD Best Practice Design Guide that will focus on the mitigation of flooding in the locality and protect development from the impact of flooding.



Underground car parking requirements

Ground storey development and accommodation of flowpaths in design.

On-Site refuge provisions

Flood Emergency Response Plans

Estimated Cost – low ($20,000) Responsibility – Council Priority – Medium

10.1.3 Response Modification Measures

10.1.3.1 Update Relevant Local Flood Plan The key improvement to emergency response considered in the current study is to incorporate the flood intelligence data borne out of the revised understanding of catchment flooding conditions. This data includes the updated flood modelling, property inundation and flood damages analysis.

It is important that the SES Plan incorporates all relevant technical data and specific community vulnerabilities (including addresses of areas at highest risk) that have been determined through the Floodplain Risk Management process. Updates to local flood emergency response would be expected to build upon the following flood intelligence data:

Update of linkage to flood warning/gauge sites and local property database

Key levels at gauge locations with references to design and historical events

Updated flood mapping showing flood depth and inundation extents and flood hazard categories for a range of events.

Property database and inundation statistics

Potential evacuation requirements

Post flood recovery services

Recommendation is to review flood emergency planning and update of Local Flood Plan utilising updated flood intelligence.

Estimated Cost – staff costs Responsibility –SES/Council Priority – High

10.1.3.2 Community Education and Awareness Program Raising and maintaining flood awareness will provide the community with an appreciation of the flood problem and what can be expected during flood events. An ongoing flood awareness program should be pursued through collaboration of the SES and Council (e.g. FloodSafe program specific for the study area). The focus of this program should encourage landowners to develop their own Flood Plan for appropriate emergency response in lieu of reliance on Emergency Services as noted above.

The Canley Corridor Floodplain Risk Management Plan included a recommendation for the development and implementation of a City-wide community education program. The Fairfield CBD catchment area would be one part of this broader LGA initiative.



Flood education programs for the Fairfield community need to recognise the cultural and linguistic diversity of the local population and cater for these needs. The Fairfield CBD catchment in particular has one of largest cultural diversities in the LGA such that appropriate flood education outcomes are required for residents of Non English Speaking Background

Estimated Cost – (incorporated in Canley Corridor Plan) Responsibility –SES/Council Priority - High

10.2 Funding and Implementation The timing of the implementation of recommended measures will depend on the available resources, overall budgetary commitments of Council and the availability of funds and support from other sources. It is envisaged that the FRM Plan would be implemented progressively over a 5 year time frame. Implementation of measures may be achieved sooner given that most measures do not require significant expenditure, however, structural upgrades will need to be incorporated in Council’s capital works program.

There are a variety of sources of potential funding that could be considered to implement the Plan. These include:

(1) Council funds;

(2) Section 94 contributions;

(3) State funding for flood risk management measures through the Office of Environment and Heritage; and

(4) State Emergency Service, either through volunteered time or funding assistance for emergency management measures.

State funds are available to implement measures that contribute to reducing existing flood problems. Funding assistance is likely to be available on a 2:1 (State:Council) basis. Although much of the FRM Plan may be eligible for Government assistance, funding cannot be guaranteed. Government funds are allocated on an annual basis to competing projects throughout the State. Measures that receive Government funding must be of significant benefit to the community. Funding is usually available for the investigation, design and construction of flood mitigation works included in the floodplain management plan.

10.3 Plan Review The FRM Plan should be regarded as a dynamic instrument requiring review and modification over time. The catalyst for change could include new flood events and experiences, legislative change, alterations in the availability of funding, or changes to the area’s planning strategies.

A thorough review every 5 years is warranted to ensure the ongoing relevance of the FRM Plan.

A summary of the recommended measures in the Plan is provided in Table 10-1.



Table 10-1 Summary of Recommended Plan Measures



FM03d - Barbara Street Culvert Inlet Upgrades and Fairlight Ave Easement Regrading

Feasibility / Concept design study of options to increase culvert system capacity discharging through railway embankment

Council, Transport for NSW

$50K (feasibility) $1.4M (design and construction)

Medium

Planning Controls Adoption of updated flood study results. Update and implement changes to LEP/DCP incorporating:

- Apply FPLs on the basis of updated flood mapping developed in the current study

- Adoption of flood planning area based on the 1% AEP + freeboard requirement

- Adoption of hydraulic category and flood risk mapping

Review of planning recommendations from Canley Corridor study


Preparation of Fairfield CBD Best Practice Design Guide.

Council $20K Medium

Improved Public Awareness Consolidation of the updated flood study flood risk mapping, flood data and flood damages database into Council’s GIS system.


Review flood affectation notations and provide flood certificates


Undertake targeted community flood education, awareness and resilience program with specific outcomes for Non English speaking community

Council, SES Staff Costs Low

Emergency Management Update and implement as required the SES Local Flood Plan to include flood intelligence data from current study

SES Staff Costs High

Property Modification Works Investigate flood proofing subsidy alternative to VHR Council $30K Low Investigate fence modification Council $10K Low

Flood proofing of individual properties Council,Landowner $20K Medium

The following recommendations are part of the adopted Canley Corridor Floodplain Risk Management Plan, are directly applicable for the Fairfield CBD catchment, and therefore endorsed as part of this Plan also:

Develop and implement City-wide community education program

Update Urban Area On-Site Detention Policy

Review DCP to ensure development controls are compatible with flood risk and other planning instruments



Costs for these recommended measures are not included in the Fairfield CBD Plan to avoid duplication.

Fairfield CBD Floodplain Risk Management Study and Plan 139 References


11 References Attorney-General’s Department (2009). Flood Preparedness Manual 20, Australian Emergency Manuals Series.

Bewsher Consulting (2006). Prospect Creek Floodplain Management Plan – Flood Study Review, prepared for Fairfield City Council

Bewsher Consulting (2010). Prospect Creek Floodplain Management Plan Review, prepared for Fairfield City Council

BMT WBM (2014). Canley Corridor Flood Study Review and Update, prepared for Fairfield City Council

BMT WBM (2016). Fairfield CBD Flood Model Review and Update, prepared for Fairfield City Council

Cardno Willing (2004). Review of Prospect Creek Flood Levels, prepared for Fairfield City Council

CSIRO (2016). State of the Climate 2016, prepared in conjunction to Bureau of Meteorology.

Dowdy A. et al. (2015). East Coast Cluster Report, Climate Change in Australia Projections for Australia’s Natural Resource Management Regions: Cluster Reports, eds. Ekström, M. et al., CSIRO and Bureau of Meteorology, Australia.

Fairfield City Council (2017). Stormwater Management Policy

Fairfield City Council (2013). Fairfield City Centre Development Control Policy

Fairfield City Council (2013). The Fairfield Local Environmental Plan

Floodmit (2011). Georges River and Prospect Creek Climate Change Sensitivity Assessment.

McLuckie D. et. al (2014). Updating National Guidance on Best Practice Flood Risk Management

McLuckie D, Babister M, Smith G, & Thomson R (2014). Updating National Guidance on Best Practice Flood Risk Management, prepared for the National Flood Risk Advisory Group and presented at the Floodplain Management Association Conference 2015.

Molino Stewart (2015). Three Tributaries Floodplain Risk Management Study and Plan, prepared for Fairfield City Council

Molino Stewart (2015). Canley Corridor Floodplain Risk Management Study and Plan, prepared for Fairfield City Council

NSW Department of Infrastructure, Planning and Natural Resources (DIPNR) (2005) Floodplain Development Manual.

NSW Department of Environment, Climate Change and Water (DECCW) (2009) NSW Sea Level Rise Policy Statement.

NSW Department of Environment, Climate Change and Water (DECCW) (2009) Draft Coastal Risk Management Guide: Incorporating sea level rise benchmarks in coastal risk assessments.

Fairfield CBD Floodplain Risk Management Study and Plan 140 References


NSW Government (2008). State Environmental Planning Policy (Exempt and Complying Development Codes.

SES (2016). The Fairfield City Local Flood Plan, prepared for Fairfield City Council

SKM (2004). Fairfield City Overland Flood Study, prepared for Fairfield City Council

SKM & FCS (2008). Flood Study for Orphan School Creek, Clear Paddock Creek and Green Valley Creek

SKM in association with Fairfield Consulting Services (FCS) (2009). Canley Corridor Flood Study, prepared for Fairfield City Council

SKM (2010). Fairfield Overland Flood Study, prepared for Fairfield City Council

Walsh C J, Roy A H, Feminella J W, Cottingham P D, Groffman P M & Morgan R P (2005). The urban stream syndrome: current knowledge and the search for a cure, Journal of the North American Benthological Society, 24(3): 706-723.

Willing and Partners (1986). St Elmos Drain Study, prepared for Fairfield City Council

Fairfield CBD Floodplain Risk Management Study and Plan A-1 Flood Mapping


Appendix A Flood Mapping



Figure A-1 20% AEP Design Event Flood Conditions









Figure A-4 PMF Event Flood Conditions



Figure A-5 20% AEP Design Event Velocity-Depth Product









Figure A-8 PMF Design Event Velocity-Depth Product



Figure A-9 20% AEP Design Event Flood Hazard









Figure A-12 PMF Design Event Flood Hazard



Figure A-13 1% AEP Design Event + 10% Increase Rainfall









Figure A-16 Flood Risk Precincts

Fairfield CBD Floodplain Risk Management Study and Plan B-1 Stakeholder and Community Consultation Material


Appendix B Stakeholder and Community Consultation Material



FAIRFIELD CBD CATCHMENT COMMUNITY FLOOD SURVEY

Council is looking at how to reduce the impact of flooding in your community. Your responses are valuable

and will help the preparation of the Fairfield CBD Floodplain Risk Management Study and Plan.

Once completed, please return this survey in the reusable envelope supplied by 21 July

2017.

About you

Address of property:-

1. Is this a residential or business address (please circle)? Residential Business

2. Do you own, rent or lease this property (please circle)? Own Rent Lease

About flooding and you

3. Have you ever experienced a flood at this property? YES NO

4. Do you have any records of flooding (photos, videos) or flood markings on your property? YES NO

5. Have you ever seen/heard any information for your local area about flooding? YES NO

6. If a flood did occur, would you know what to do to protect yourself and your property? YES NO

7. Have you prepared a written plan (i.e. flood plan) for your household / business to follow

during a flood? YES NO

8. Do you know who to contact if there is a flood (please tick)?

Fairfield City Council Emergency 000 NSW State Emergency Service (SES) Not sure

9. If a flood did occur would you prefer to stay in your house or evacuate (please tick)?

Stay in house Evacuate Not sure

About Flooding and Council

9. What assistance would you like Council to provide to help you be prepared for flooding (please tick)?

Workshop Online information Flood Preparedness Pack

Other__________ Not sure



11. Who in the community should be responsible for reducing flood risks? (more than one answer allowed)

Fairfield City Council NSW State Emergency Service (SES) Landowner/Resident

NSW Government Someone else (please tell us who)

12. Do you think Council should spend more on flooding controls and flood awareness in your area? YES NO

Options to reduce flooding

13. Below is a list of flood mitigation measures which could help reduce flooding in your community. The

enclosed brochure provides further information about some of these measures.

Please circle your preference on a scale from 1 to 10 (1 = less preferred, 10=most preferred).

Flood education to show you how to prepare for and deal with floods 1 2 3 4 5 6 7 8 9 10

Preparation of a Local Flood Plan which will be used by the local SES 1 2 3 4 5 6 7 8 9 10

Development controls/constraints, especially floor-level controls,

fencing controls and building material controls for new developments 1 2 3 4 5 6 7 8 9 10

Construction of new detention basins in open space/park areas 1 2 3 4 5 6 7 8 9 10

Increasing the capacity of existing detention basins 1 2 3 4 5 6 7 8 9 10

On-site detention (i.e. holding water on your property) 1 2 3 4 5 6 7 8 9 10

Channel enhancement by removing flow restrictions in our creeks 1 2 3 4 5 6 7 8 9 10

Creek restoration by removing concrete channels and replace them with

wider, natural creek lines 1 2 3 4 5 6 7 8 9 10

Flood levees or flow diversions to redirect water flow 1 2 3 4 5 6 7 8 9 10

Flow diversions in streets to redirect water flow along roads 1 2 3 4 5 6 7 8 9 10

Floodgates at the creek to stop flood water backing up in the drain

when the creek floods 1 2 3 4 5 6 7 8 9 10

Large scale redevelopment, planning developments with flooding and

other water sensitive design elements 1 2 3 4 5 6 7 8 9 10

Voluntary purchase where Council can buy your property 1 2 3 4 5 6 7 8 9 10

Voluntary house raising where Council can provide financial assistance to raise your house above a certain flood level 1 2 3 4 5 6 7 8 9 10



Flood proofing of your home with water resistant materials 1 2 3 4 5 6 7 8 9 10

Non-voluntary fencing controls , restricting the type of fence you can use 1 2 3 4 5 6 7 8 9 10

Voluntary fence modification, having open-style fences on your property 1 2 3 4 5 6 7 8 9 10

14. If Council offered financial assistance to change the type of fence on your property to a more flood-friendly

fence, would you consider the voluntary fence modification option more favourably? YES NO

15. Would you be willing to change your fence to an open-style fence if Council could NOT provide you with

any financial assistance? YES NO

Information in this survey will remain confidential, and will only be used to assist Council in its planning for how to best

minimise the effects of flooding in the Fairfield CBD catchment.

Fairfield CBD Floodplain Risk Management Study and Plan C-1 Flood Modification Options – Afflux Mapping


Appendix C Flood Modification Options – Afflux Mapping

Note: Figure C-1 to Figure C-15 present results for the 5% AEP and 1% AEP design events for all modelled options

Figure C-16 to Figure C-20 present results for the 20% AEP design event for selected options targeting this event



Figure C-1 FM01a Nelson St/Ware St Drainage –Change in Peak Flood Level



Figure C-2 FM01b Nelson St/Ware St Regrading – Change in Peak Flood Level



Figure C-3 FM02a Barbara St/Hamilton Rd Drainage –Change in Peak Flood Level



Figure C-4 FM02b Barbara St/Hamilton Rd Regrading –Change in Peak Flood Level



Figure C-5 FM03a Barbara St Railway Culvert Upgrade –Change in Peak Flood Level



Figure C-6 FM03b Barbara St Inlet Capacity Upgrade –Change in Peak Flood Level



Figure C-7 FM04 Hamilton Rd Drainage (Eustace/Sackville) – Change in Peak Flood Level



Figure C-8 FM05 Hamilton Rd Drainage (Sackville/Thomas) – Change in Peak Flood Level



Figure C-9 FM06 Railway Parade Culvert Inlet – Change in Peak Flood Level



Figure C-10 FM07 St Elmos Drain Surface Drainage – Change in Peak Flood Level



Figure C-11 FM09 Channel Bunding Hamilton Rd – Change in Peak Flood Level



Figure C-12 FM13 Detention Basins – Change in Peak Flood Level



Figure C-13 FM14 Easement Regrading (Lyndon St/Wilga St) – Change in Peak Flood Level



Figure C-14 FM03c Barbara St Railway Culvert and Inlet Upgrade –Change in Peak Flood Level



Figure C-15 FM03d Barbara St Railway Culvert /Inlet /Easement –Change in Peak Flood Level



Figure C-16 FM01a Nelson St/Ware St Drainage –Change in Peak Flood Level



Figure C-17 FM01b Nelson St/Ware St Regrading – Change in Peak Flood Level



Figure C-18 FM04 Hamilton Rd Drainage (Eustace/Sackville) – Change in Peak Flood Level



Figure C-19 FM05 Hamilton Rd Drainage (Sackville/Thomas) – Change in Peak Flood Level



Figure C-20 FM06 Railway Parade Culvert Inlet – Change in Peak Flood Level

Fairfield CBD Floodplain Risk Management Study and Plan D-1 Flood Damages Inputs


Appendix D Flood Damages Inputs



Table D1 – Residential Damage Curve Inputs

Version 1.00PROJECT DATE

BUILDINGSRegional Cost Variation Factor 1.00 From RawlinsonsPost late 2001 adjustments 1.75 Changes in Avge Weekly Earnings - www.abs.gov.auPost Flood Inflation Factor 1.00 1.0 to 1.5

Multiply overall structural costs by this factor Judgement to be used. Some suggestions belowRegional City Regional Town

Houses Affected Factor Houses Affected FactorSmall scale impact < 50 1.00 < 10 1.00

Medium scale impacts in Regional City 100 1.20 30 1.30Large scale impacts in Regional City > 150 1.40 > 50 1.50

Typical Duration of Immersion 2 hoursBuilding Damage Repair Limitation Factor 0.75 due to no insurance short duration flood long duration flood

Suggested range 0.75 to 0.85Average House Size 190 m 2̂ 240 m^2 is BaseBuilding Size Adjustment 0.8Total Building Adjustment Factor 1.04CONTENTSAverage Contents Relevant to Site 47,500$ Base for 240 m^2 house 60,000$ Post late 2001 adjustments 1.75 From aboveContents Damage Repair Limitation Factor 0.75 due to no insurance short duration flood long duration floodSub-Total Adjustment Factor 0.85 Suggested range 0.75 to 0.85Level of Flood Awareness low low or high only. Low default unless otherwise justifiable.Effective Warning Time 1 hourInterpolated DRF adjustment (Awareness/Time) 0.98Typical Table/Bench Height (TTBH) 0.90 0.9m is typical height. If typical is 2 storey house use 2.6m.Total Contents Adjustment Factor AFD <= TTBH 0.83Total Contents Adjustment Factor AFD > TTBH 0.85Most recent advice from Victorian Rapid Assessment MethodLow level of awareness is expected norm (long term average) any deviation needs to be justified.Basic contents damages are based upon a DRF of 0.9Effective Warning time (hours) 0 3 6 12 24RAM AIDF Inexperienced (Low awareness) 0.90 0.80 0.80 0.80 0.70DRF (ARF/0.9) 1.00 0.89 0.89 0.89 0.78RAM AIDF Experienced (High awareness) 0.80 0.80 0.60 0.40 0.40DRF (ARF/0.9) 0.89 0.89 0.67 0.44 0.44Site Specific DRF (SRF/0.9) for Awareness level for iteration 1.00 0.89 0.89 0.89 0.78Effective Warning time (hours) 0 3 1Site Specific iterations 1.00 0.89 0.98ADDITIONAL FACTORSPost late 2001 adjustments 1.75 From aboveExternal Damage 6,700$ $6,700 recommended without justificationClean Up Costs 4,000$ $4,000 recommended without justificationLikely Time in Alternate Accommodation 2 weeksAdditional accommodation costs /Loss of Rent 220$ $220 per week recommended without justificationTWO STOREY HOUSE BUILDING & CONTENTS FACTORSUp to Second Floor Level, less than 2.6 m 70% Single Storey Slab on GroundFrom Second Storey up, greater than 2.6 m 110% Single Storey Slab on GroundBase Curves AFD = Above Floor DepthsSingle Storey Slab on Ground/Low Set 13164 + 4871 x AFD in metresStructure w ith GST AFD greater than 0.0 mValidity Limits AFD less than or equal to 6 mSingle Storey High Set 16586 + 7454 x AFDStructure w ith GST AFD greater than -1.50 mValidity Limits AFD less than or equal to 6 mContents 20000 + 20000 x AFDContents w ith GST AFD greater than 0Validity Limits AFD less than or equal to 2

DETAILS

SITE SPECIFIC INFORMATION FOR RESIDENTIAL DAMAGE CURVE DEVELOPMENT

JOB No.Queries to [email protected]



Table D2 – Residential Depth-Damage Relationship

Floodplain Specific Damage/Aftermath CurvesAllowance for Waves 0 mSteps in Curve 0.1 m

Single Storey Slab on Ground/Low Set Single Storey High Set 2 Storey Houses

Static AFD AFD + Wave Action

Damage Static AFD AFD + Wave Action

Damage Static AFD AFD + Wave Action

Damage

-0.50 -0.50 11,725$ -1.50 -1.50 11,725$ -0.50 -0.50 11,725$ -0.40 -0.40 11,725$ -1.40 -1.40 18,116$ -0.40 -0.40 11,725$ -0.30 -0.30 11,725$ -1.30 -1.30 18,890$ -0.30 -0.30 11,725$ -0.20 -0.20 11,725$ -1.20 -1.20 19,665$ -0.20 -0.20 11,725$ -0.10 -0.10 11,725$ -1.10 -1.10 20,439$ -0.10 -0.10 11,725$ 0.00 0.00 25,403$ -1.00 -1.00 21,214$ 0.00 0.00 21,300$ 0.10 0.10 48,209$ -0.90 -0.90 21,988$ 0.10 0.10 37,264$ 0.20 0.20 50,036$ -0.80 -0.80 22,763$ 0.20 0.20 38,543$ 0.30 0.30 51,863$ -0.70 -0.70 23,537$ 0.30 0.30 39,822$ 0.40 0.40 53,690$ -0.60 -0.60 24,312$ 0.40 0.40 41,101$ 0.50 0.50 55,517$ -0.50 -0.50 25,086$ 0.50 0.50 42,379$ 0.60 0.60 57,344$ -0.40 -0.40 25,861$ 0.60 0.60 43,658$ 0.70 0.70 59,171$ -0.30 -0.30 26,635$ 0.70 0.70 44,937$ 0.80 0.80 60,998$ -0.20 -0.20 27,410$ 0.80 0.80 46,216$ 0.90 0.90 62,825$ -0.10 -0.10 28,184$ 0.90 0.90 47,495$ 1.00 1.00 65,151$ 0.00 0.00 50,187$ 1.00 1.00 49,123$ 1.10 1.10 67,003$ 0.10 0.10 52,307$ 1.10 1.10 50,419$ 1.20 1.20 68,855$ 0.20 0.20 54,428$ 1.20 1.20 51,716$ 1.30 1.30 70,706$ 0.30 0.30 56,548$ 1.30 1.30 53,012$ 1.40 1.40 72,558$ 0.40 0.40 58,668$ 1.40 1.40 54,308$ 1.50 1.50 74,410$ 0.50 0.50 60,789$ 1.50 1.50 55,605$ 1.60 1.60 76,262$ 0.60 0.60 62,909$ 1.60 1.60 56,901$ 1.70 1.70 78,114$ 0.70 0.70 65,029$ 1.70 1.70 58,197$ 1.80 1.80 79,966$ 0.80 0.80 67,149$ 1.80 1.80 59,494$ 1.90 1.90 81,818$ 0.90 0.90 69,270$ 1.90 1.90 60,790$ 2.00 2.00 83,670$ 1.00 1.00 71,390$ 2.00 2.00 62,087$ 2.10 2.10 84,176$ 1.10 1.10 73,510$ 2.10 2.10 62,441$ 2.20 2.20 84,682$ 1.20 1.20 75,631$ 2.20 2.20 62,795$ 2.30 2.30 85,188$ 1.30 1.30 77,751$ 2.30 2.30 63,149$ 2.40 2.40 85,694$ 1.40 1.40 79,871$ 2.40 2.40 63,504$

2.50 2.50 86,201$ 1.50 1.50 81,992$ 2.50 2.50 63,858$

2.60 2.60 86,707$ 1.60 1.60 84,112$ 2.60 2.60 64,212$

2.70 2.70 87,213$ 1.70 1.70 86,232$ 2.70 2.70 94,762$

2.80 2.80 87,719$ 1.80 1.80 88,353$ 2.80 2.80 95,318$

2.90 2.90 88,225$ 1.90 1.90 90,473$ 2.90 2.90 95,875$

3.00 3.00 88,731$ 2.00 2.00 92,593$ 3.00 3.00 96,432$

3.10 3.10 89,237$ 2.10 2.10 93,368$ 3.10 3.10 96,988$

3.20 3.20 89,743$ 2.20 2.20 94,142$ 3.20 3.20 97,545$

3.30 3.30 90,249$ 2.30 2.30 94,917$ 3.30 3.30 98,102$

$0

$20,000

$40,000

$60,000

$80,000

$100,000

$120,000

-2.00 -1.00 0.00 1.00 2.00 3.00 4.00

Floo

d D

amag

e

Flood Depth

Floodplain Specific Flood Damage Curves

Single Storey Slab on Ground/Low SetSingle Storey High Set2 Storey Houses



Table D3 – Commercial/Industrial Depth-Damage Relationship

Depth Shops and small retailers Industrial propertiesabove up to approx. 200m square Between approx. 200m and 600m square Large Commercial & Industrialwork CODE CODE CODE CODE CODE CODE CODE CODEarea CL CM CH IL IM IH L1 L2(m) offset = offset = offset = offset = offset = offset = offset = offset =

1 2 3 4 5 6 7 8-999999 $0 $0 $0 $0 $0 $0 $0 $0

0 $0 $0 $0 $0 $0 $0 $0 $00.01 $612 $3,672 $7,038 $5,202 $10,710 $21,420 $30,600 $428,4000.05 $3,672 $9,180 $15,912 $14,076 $26,622 $53,244 $214,200 $642,6000.1 $7,038 $15,912 $31,824 $26,622 $53,244 $106,488 $214,200 $642,6000.2 $15,300 $30,600 $64,260 $52,020 $107,100 $214,200 $642,600 $642,600

0.25 $21,420 $39,780 $79,560 $64,260 $125,460 $247,860 $703,800 $642,6000.3 $24,480 $45,900 $88,740 $70,380 $140,760 $284,580 $826,200 $642,6000.4 $30,600 $58,140 $115,362 $88,740 $177,480 $354,960 $887,400 $673,2000.5 $33,660 $70,380 $140,760 $107,100 $214,200 $425,340 $918,000 $703,8000.6 $39,780 $82,620 $159,120 $125,460 $247,860 $495,720 $1,071,000 $703,8000.7 $44,370 $93,942 $184,518 $149,022 $283,968 $567,936 $1,193,400 $765,000

0.75 $52,020 $107,100 $195,840 $159,120 $302,940 $602,820 $1,254,600 $795,6000.8 $53,550 $110,160 $205,938 $166,770 $319,464 $638,928 $1,438,200 $795,6000.9 $55,080 $113,220 $229,500 $177,480 $354,960 $709,920 $1,774,800 $887,400

1 $61,200 $125,460 $247,860 $195,840 $391,680 $761,940 $2,142,000 $1,071,0001.1 $65,790 $133,110 $266,220 $205,938 $418,914 $827,118 $4,284,000 $887,4001.2 $70,380 $140,760 $284,580 $214,200 $443,700 $887,400 $6,242,400 $1,071,000

1.25 $73,440 $149,940 $302,940 $229,500 $462,060 $924,120 $7,129,800 $1,621,8001.3 $74,358 $153,000 $305,388 $234,396 $468,486 $933,300 $7,497,000 $1,713,6001.4 $75,276 $156,060 $312,120 $241,434 $482,868 $954,720 $8,568,000 $1,927,8001.5 $76,500 $159,120 $318,240 $247,860 $495,720 $976,140 $8,935,200 $2,142,000

1.75 $82,620 $168,300 $336,600 $266,220 $514,080 $1,028,160 $8,935,200 $6,242,4002 $88,740 $177,480 $354,960 $284,580 $532,440 $1,064,880 $8,935,200 $8,935,2003 $91,800 $183,600 $367,200 $290,700 $535,500 $1,071,000 $8,935,200 $8,935,200

9999999 $91,800 $183,600 $367,200 $290,700 $535,500 $1,071,000 $8,935,200 $8,935,200

BMT WBM Bangalow 6/20 Byron Street, Bangalow 2479

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Documents

Fairfield CBD Floodplain Risk Management Study …...Fairfield CBD Floodplain Risk Management Study and Plan iv Executive Summary K:\S20152_Fairfield_CBD_FRMSP\Docs\R.S20152.001.03