1

EFFECT OF REGI LALMA HOUSING SCHEME ON FUTUREFLOODS

Author

Mohamed Reg:08PWAGR0584

Bakhta noor Reg:08PWAGR0582

Supervisor

Dr. Muhammad Ibrahim

DEPARTMENT OF AGRICULTRUAL ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGYPESHAWAR

2011-2012

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EFFECT OF REGI LALMA HOUSING SCHEME ON FUTUREFLOODS

This Project Thesis is submitted in partial fulfillment of therequirements for award of the degree of the degree of

Bachelor of Science

In

Agricultural Engineering

DEPARTMENT OF AGRICULTURAL ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGY

PESHAWAR, PAKISTAN

3

SESSION: 2011-2012

EFFECT OF REGI LALMA HOUSING SCHEME ON FUTURE

FLOODS

A thesis submitted in partial fulfillment of the requirement for the award of degree of

B.Sc. in Agricultural Engineering.

Submitted By

Bakhta Noor Mohamed

08PWAGR0582 08PWAGR0584

Supervised by

Dr. Muhammad Ibrahim

Department of Agricultural Engineering

External Examiner’s Signature: ________________________________________

Thesis Supervisor’s Signature: ________________________________________

(Dr. Muhammad Ibrahim)

Chairman’s Signature: ________________________________________

(Prof. Dr. Taj Ali Khan)

DEPARTMENT OF AGRICULTURAL ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLOGY

PESHAWAR, PAKISTAN

SESSION: 2011-2012

4

Abstract

The aim of this project is to determine the effect of proposed development of

Regi Lalma Housing Scheme (RLHS) on future floods. During the proposed

development the permeable soil is converted into impermeable soil cover such as

roads, parking lots, pavements and roof tops. To estimate the discharges before and

after proposed development we have three methods, Anderson method, Snyder

method and Regression method.

From the study and the results obtained from the three different methods. It is

concluded the urbanization is the cause of the flood. The discharge before the

development by any of the above three method is less than the discharge after the

development. Due to this it is believed that urbanization is the cause of the flood.

Flood cause severe problems. It destroyed fertile land, crops, buildings, roads, houses,

aquatic habitat, pollute water, cause epidemic diseases, affect large number of people

and most important cause the loss of precious lives. Hence it is necessary to take such

steps during development to eliminate or reduce the impact of flood.

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ACKNOWLEDGEMENT

Firstly, all praise is due to almighty ALLAH who bestowed upon us health

and opportunity to successfully complete our B.Sc thesis. Countless salutation is upon

the holy prophet Hazrat Muhammad (peace be upon him), the most perfect and a

torch of guidance and knowledge for humanity as a whole.

We would like to express our deepest gratitude and would like to gratefully

acknowledge the enthusiastic supervision of Dr.Muhammad Ibrahim our esteemed

promoter during this work, which has supported us throughout our work with his

patience and knowledge whilst allowing us the room to work in our own way. His

steadfast encouragement, guidance, support, kind concern and consideration from the

initial to the final level enabled us to develop an understanding of the subject. He has

been our inspiration as we hurdled all the obstacles in the completion of this research

work.

We are also thankful to our chairman Prof. Dr. Taj Ali Khan, department of

agricultural engineering, for developing our mental level to an extent to tackle any

kind of hurdles.

It would be injustice if we do not endorse the continuous support of Engr.

Khurram Sheraz (lecturer Agri Deptt) and Engr, Muhammad Ajmal (lecturer Agri

Deptt) who despite the distance painstakingly guided us.

Las, but not least, we warmly thank our parents for their financial and spiritual

support in all aspects of our life, and who pray for our success, ceaselessly, without

which we would certainly have not been able to achieve our goals.

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LIST OF FIGURES

Number Page No.

Figure 1.1 Effect of urban development on flood………………………………..2

Figure 1.2 Hydrograph before and after development of Mercer Creek, western

Washington USA……………………………………………………...4

Figure 2.1 Increased runoff peaks and volumes increase stream flows………….7

Figure 2.2 Dubai in (1990) before development and (2007) after development….8

Figure 2.3 Wet pond……………………………………………………………..10

Figure 2.4 Storm water Wetland………………………………………………...11

Figure 2.5 Dry pond……………………………………………………………..12

Figure 2.6 Photograph of constructed infiltration basin at the Pony Express Car

Wash in Oak Park Heights…………………………………………...12

Figure 2.7 Vegetated filter strip photo by University of Illinois Extension……..13

Figure 2.8 Photograph of grassed swale east of CR 13, Lake Elmo Dental

Clinic…………………………………………………………………14

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LIST OF TABLES

Number Page No.

Table 3.1: Calculated data for Anderson method………………………………..22

Table 3.2: Anderson Time lag computation……………………………………..22

Table 3.3: Anderson flood frequency ratio……………………………………...24

Table 3.4: Calculated data for Snyder method…………………………………..27

Table 3.5: Ct values for Snyder method…………………………………………27

Table 3.6: Discharge estimation for Snyder method before development………29

Table 3.7: Discharge estimation for Snyder method after development………...30

Table 3.8: Proposed condition for BDF…………………………………………31

Table 3.9: Results of estimated discharges of different methods………………..32

Table 4.1: Results of estimated discharges before and after development…………..33

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TABLE OF CONTENTS

Abstract……………………………………………………………………………….. i

Acknowledgement…………………………………………………………………… ii

List of figures………………………………………………………………………... iii

List of tables………………………………… ……………………………………….iv

Chapter 1: Introduction…………………………………………………………... 1

1.1: Background………………… ………………………………...1

1.1.1: Effect of urban development on floods…… ………….2

1.1.2: Hydrologic effect of urban development… …………..2

1.2: Statement of Problem………………………………………….4

1.3: Objectives……………………………………………………. 5

1.4: Scope of the study……………………………………………. 5

Chapter 2: Literature review………………………… …………………………...6

2.1: Flood……………………………….. ………………………...6

2.2: Types of flood……………... …………………………………6

2.2.1: Urban flooding…………….......................................... 6

2.2.2: Changes to stream flow………………………………. 6

2.3: Urban storm water management……………………………... 8

2.4: Storm water management system……………………………. 8

2.4.1: Lot-level and conveyance controls………………… 9

2.4.2: Soak way pits/Infiltration trenches………………….9

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2.4.3: End-of-pipe controls………………………………... 10

2.4.3.1: Wet ponds……. ……………………10

2.4.3.2: Wetlands……………. ………………11

2.4.3.3; Dry ponds…………………………… 11

2.4.3.4: Infiltration basin… …………………..12

2.4.3.5: Filters………………… ……………..13

2.4.3.6: Vegetated filter strips……………….. 13

2.4.3.7: Grassed swales…….. ………………..13

2.5: Important of storm water management……… ……………………...14

2.6: History………………………………………………………………. 15

2.7: Discharge measurement methods………………. …………………..16

2.7.1: Anderson method………………….. ………………………..16

2.7.2: Snyder method………………………. ……………………...17

2.7.3: Regression method…………… ……………………………18

Chapter 3: Materials and methods……………… …………………………………..20

3.1: Site…………………………… ……………………………………..20

3.2: Research parameters………………………. ………………………..20

3.2.1: Catchment area……………………………………………… 20

3.2.2: Impervious surface……………… …………………………..20

3.2.3: Time lag……………………… ……………………………..20

3.2.4: Time of concentration……………………………………… 21

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3.2.5: Length of main stream……………………………………… 21

3.2.6: Slope…………. ……………………………………………..21

3.3: Methodology…………………………………………………………21

3.3.1: Anderson method…………………………………………… 21

3.3.2: Snyder method…………………. …………………………...26

3.3.3: Regression method…………………………………………..31

Chapter 4: Results and discussion………. ……………………………………...33

Chapter 5: Conclusion and recommendation…………………………………… 35

5.1: Conclusion………………… ………………………………………..35

5.2: Recommendation…………….. ……………………………………..35

5.2.1: Storage controls……………… ……………………………..35

5.2.2: Infiltration controls…………………. ……………………....35

5.2.3: End-of-pipe controls……………………… ………………...36

References…………………………… ……………………………………………...37

Appendix ………………………………….. ………………………………………..39

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Google earth picture of the Regi Lalma

Catchment area of the Takhta Beg Khawar near the Regi Lalma

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CHAPTER 1

INTRODUCTION

1.1 Back ground

Urbanization is the process by which large numbers of people become

permanently concentrated in small areas forming cities. The definition of a city or an

urban area changes from time to time and place to place. The United Nations

Organization has recommended that member countries regard all places with more

than 20,000 inhabitants living close together as urban.

Floods risk thought out the World in the past was not as high as today or will be

in future. The reasons are that Urbanization was not at the alarming rate, the people

were scattered in small’s villages and lived simple lives without so much

infrastructures like buildings, roads, pavements and concrete houses. When rainfall

occurred, some of the rainwater was infiltrated directly into the soil, some amount of

the rainwater was stored in the watershed in the natural detention ditches and some

fraction was absorbed by vegetation. The result was that the frequency and peak

volume of the flood was less.

The influence of humans on the physical and biological systems of the Earth’s

surface is not a recent manifestation of modern societies; instead, it is ubiquitous

throughout our history. As human populations have grown, so has their footprint,

such that between 30 and 50 percent of the Earth’s surface has now been transformed.

Most of this land area is not covered with pavement; indeed, less than 10 percent of

this transformed surface is truly “urban”. However, urbanization causes extensive

changes to the land surface beyond its immediate borders, particularly in ostensibly

rural regions, through alterations by agriculture and forestry that support the urban

population. Within the immediate boundaries of cities and suburbs, the changes to

natural conditions and processes brought by urbanization are among the most radical

of any human activity. [1]

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1.1.1 Effect of urban develop ment on floods

The changes in land use associated with urban development affect flooding in

many ways. Removing vegetation and soil, grading the land surface, and constructing

drainage networks increase runoff to streams from rainfall and snowmelt. As a result,

the peak discharge, volume, and frequency of floods increase in nearby streams.

Changes to stream channels during urban development can limit their capacity to

convey floodwaters. Roads and buildings constructed in flood-prone areas are

exposed to increased flood hazards, including inundation and erosion, as new

development continues. Information about stream flow and how it is affected by land

use can help communities reduce their current and future vulnerability to floods.

1.1.2 Hydrologic effects of urban development

Streams are fed by runoff from rainfall moving as overland or subsurface flow.

Floods occur when large volumes of runoff flow quickly into streams and rivers. The

peak discharge of a flood is influenced by many factors, including the intensity and

duration of storms, the topography and geology of stream basins, vegetation, and the

hydrologic conditions preceding storm events.

Fig 1.1: Effects of Urban development on Flood

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Figure 1.1 illustrates how impervious cover and urban drainage systems

increase runoff to creeks and rivers. The larger volume, velocity and duration of flow

acts like sandpaper on stream banks, intensifying the erosion and sediment transport

from the landscape and stream banks. This often causes channel erosion, clogged

stream channels and habitat damage. [2]

Land use and other human activities also influence the peak discharge of

floods by modifying how rainfall and snowmelt are stored on and run off the land

surface into streams. In undeveloped areas such as forests and grasslands, rainfall and

snowmelt collect and are stored on vegetation, in the soil column, or in surface

depressions. When this storage capacity is filled, runoff flows slowly through soil as

subsurface flow. In contrast, urban areas, where much of the land surface is covered

by roads, buildings and parking lots, have less capacity to store rainfall and snowmelt.

Construction of roads and buildings often involves removing vegetation, soil, and

depressions from the land surface. The permeable soil is replaced by impermeable

surfaces such as roads, roofs, parking lots, and sidewalks that store little water, reduce

infiltration of water into the ground, and accelerate runoff to ditches and streams.

Even in suburban areas, where lawns and other permeable landscaping may be

common, rainfall and snowmelt can saturate thin soils and produce overland flow,

which runs off quickly. Dense networks of ditches and culverts in cities reduce the

distance that runoff must travel overland or through subsurface flow paths to reach

streams and rivers. Once water enters a drainage network, it flows faster than either

overland or subsurface flow.

With less storage capacity for water in urban basins and more rapid runoff, urban

streams rise more quickly during storms and have higher peak discharge rates than do

rural streams. In addition, the total volume of water discharged during a flood tends to

be larger for urban streams than for rural streams. For example, stream flow in

Mercer Creek, an urban stream in western Washington, increases earlier and more

rapidly, has a higher peak discharge and volume during the storm on February 1,

2000, and decreases more rapidly than in Newaukum Creek, a nearby rural stream. As

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with any comparison between streams, the differences in stream flow cannot be

attributed solely to land use, but may also reflect differences in geology, topography,

basin size and shape, and storm patterns. [3]

The hydrologic effects of urban development often are greatest in small stream

basins where, prior to development, much of the precipitation falling on the basin

would have become subsurface flow, recharging aquifers or discharging to the stream

network further downstream. Moreover, urban development can completely transform

the landscape in a small stream basin, unlike in larger river basins where areas with

natural vegetation and soil are likely to be retained.

Figure 1.2 illustrates that stream flow in Mercer Creek , an urban stream in

western Washington, increases more quickly, reaches a higher peak discharge, and

has a larger volume during a one-day storm on February 1, 2000, than stream flow in

Newaukum Creek, a nearby rural stream. Stream flow during the following week,

however, was greater in Newaukum Creek.

Fig 1.2: Hydrograph before and after development of Mercer Creek, Western

Washington USA.

1.2 Statement of Problem

The aim of this study is to determine the impact of urbanization of Regi

lalama Housing scheme on future flood in the Takhta Beg Khawar by estimating the

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peak discharge before and the proposed development of the Housing Scheme.

The existing site of Regi lalma Housing Scheme (RLHS) consist of bar soil

having high infiltration rate. The proposed development of RLHS will convert

approximately 60% area of permeable soil to impermeable cover such as roads,

parking lots and roof tops. It is believed that reduced infiltration after development

will generate excess runoff and may overflow the Takhta Beg Khawar in future.

Floods cause disasters such as water pollution, destruction of aquatic habitats,

erosion of fertile lands, epidemic diseases, loss of precious properties, and loss of

animals and at last the most important is the loss of human life. This shows that

flood managements are necessary to control or at least minimize these losses.

1.3 Objectives

To determine the effect of proposed development of RLHS on future flood in

Takhta Beg Khawar.

To recommend different options for managing the excess runoff thus

generated by proposed development of RLHS.

1.4 Scope of the study:

In Pakistan, the 2010 and 2011 floods were due to climatic changes

according to the UN, but in 1996, Lahore city faced severe urban storm due to 500

mm rainfall in 24 hours. [4]. the flood caused severe problems. It has destroyed

fertile land, crops, buildings, roads, houses, aquatic habitat, pollute the water, cause

epidemic diseases, affect large number of people and also cause the loss of precious

lives. It is necessary to discuss how urbanization causes the flood, so that we become

able to take the necessary steps like Best Management Practices for storm water

management to reduce the effect of urbanization on flood.

It is hoped that the results of this study will produce a better understanding of

urbanization and its effect on storm runoff. An attempt has been made to present the

results of this study in such a way that it may be used to further advance the

understanding of laymen. Hopefully planners will also be able to use the results to

make better land use and development decisions.

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CHAPTER 2

LITERATURE REVIEW

2.1 Flood

A flood is an excess of water on land that’s normally dry and is a situation

where inundation is caused by high flow, or overflow of water in as established

watercourse, such as a river, stream, or drainage ditch; or ponding of water at or near

the point where the rain fell. A flood can strike anywhere without warning, it occurs

when a large volume of rain falls within a short time.

2.2 Types of flooding

According to duration: Slow- Onset Flooding, Rapid-Onset Flooding, and

Flash Flooding.

According to Location: Coastal Flooding, Arroyos Flooding, River Flooding

and Urban Flooding.

2.2.1 Urban Flooding

The Urban area is paved with roads, buildings, rooftops, parking lots, and

pavements, and the discharge of heavy rainfall can’t absorbed into the ground due to

drainage constraints leads to flooding of streets, underpasses and low laying areas.[5]

2.2.2 Changes to Stream Flow

Urban development alters the hydrology of watersheds and streams by

disrupting the natural water cycle. This results in:

Increased Runoff Volumes – Land surface changes can

dramatically increase the total volume of runoff generated in a

developed watershed as seen in Figure 2.1

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Increased Peak Runoff Discharges – Increased peak discharges for a

developed watershed can be two to five times higher than those for an

undisturbed watershed.

Greater Runoff Velocities – Impervious surfaces and compacted soils,

as well as improvements to the drainage system such as storm drains,

pipes and ditches, increase the speed at which rainfall runs off land

surfaces within a watershed.

Timing – As runoff velocities increase, it takes less time for water to

run off the land and reach a stream or other water body.

Increased Frequency of Bank full and Near Bank full Events – Increased

runoff volumes and peak flows increase the frequency and duration of

smaller bank full and near bank full events (see Figure 2.1) which are the

primary channel forming events.

Increased Flooding – Increased runoff volumes and peaks also

increase the frequency, duration and severity of out-of-bank flooding

as shown in Figure 2.1

Lower Dry Weather Flows (Base flow) – Reduced infiltration of stormwater runoff

causes streams to have less base flow during dry weather periods and reduces the

amount of rainfall recharging groundwater aquifers.(GSMVol1– August 2001).

Fig 2.1 Increased Runoff Peaks and Volumes Increase Stream Flows. [6]

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2.3 Urban Storm water Management

Storm water management involves the control of surface runoff. The volume

and rate of runoff both substantially increase as land development occurs.

Construction of impervious surfaces, such as roofs, parking lots and roadways and the

installation of storm sewer pipes which efficiently collect and discharge runoff,

prevent the infiltration of rainfall into the soil. Management of storm water runoff is

necessary to compensate for possible impacts of impervious surfaces such as

decreased groundwater recharge, increased frequency of flooding, stream channel

instability, concentration of flow on adjacent properties, and damage to transportation

and utility infrastructure. [7]

Fig 2.2: Dubai in (1990) before development and (2007) after development. [8]

A storm water management control, measure or practice, such as a grassed

swale or wet pond, is an individual element of a system. It may be a lot-level,

conveyance, or end-of-pipe control. A practice may perform one or more functions,

such as pretreatment or treatment, infiltration or storage for flood and erosion control.

2.4 Storm water management system

A storm water management system or treatment train is a series of practices

that meets storm water management objectives for an area. For example, rear yard

soak away pits (a lot-level control), grassed swales (a conveyance control) and a wet

pond (an end-of-pipe control) may comprise a treatment train.

Unfortunately, the effects of urbanization cannot be mitigated through

prevention alone. A storm water management “treatment train” is a series of practices

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that meets storm water management objectives for a given area. The “treatment train”

approach combining lot-level, conveyance and end-of-pipe controls is required to

meet the multiple objectives. Lot-level controls are those that are applied on

individual lots (e.g. on residential properties) or for areas less than two hectares. The

storm water runs off the lot into a ditch or a sewer which is part of the conveyance

system. The conveyance system drains or conveys the runoff from the lots to an end-

of pipe facility. End-of-pipe control facilities are those that receive storm water runoff

from a conveyance system and discharge the treated water to receiving waters

(usually a lake or stream).

2.4.1 Lot-level and Conveyance controls

Most lot-level and conveyance controls may be classified either as storage

controls or infiltration controls. Storage controls are designed to temporarily store

storm water runoff and release it at a controlled rate. Although the volume of runoff

does not decrease, the risk of flooding is reduced because all the storm water runoff

does not arrive at the stream at the same time.

The primary function of infiltration controls is to promote infiltration into the

ground in order to maintain the natural hydrologic cycle. This can be best

accomplished by lot-level infiltration controls because these can best recreate the pre-

development conditions.

Infiltration techniques can achieve water quality enhancement. However,

these measures are ideally suited for the infiltration of relatively clean storm water

including rooftop and foundation drainage. Storm water containing lots of sediment

can plug infiltration controls unless the sediment is first removed.

2.4.2 Soak away Pits/ Infiltration Trenches

Soak away pits and infiltration trenches are stone-filled (golf ball size)

excavations where storm water runoff collects and then infiltrates into the ground.

Infiltration trenches receive storm water from several lots in contrast to soak away

pits which are used for individual lots. A filter layer at the base of the trench provides

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water quality enhancement of the storm water as it moves into the surrounding soils.

There practices can only be used where soils allow the trench to empty within a

reasonably short time.

2.4.3 End-of-Pipe Controls

End-of-pipe facilities are usually required for flood and erosion control and

water quality improvement, although lot-level and conveyance controls can reduce

the size of the end-of-pipe facilities required. End-of pipe controls

Wet ponds

Wetlands

Dry ponds

Filters

Infiltration basins

2.4.3.1 Wet pond

A wet pond is a detention basin designed to temporarily store collected

stormwater runoff and release it at a controlled rate. It is different from a dry pond in

that it maintains a permanent pool of water between storm events. Wet ponds are the

most common end-of-pipe stormwater facility used in Ontarion. A single wet pond

can provide water quality, erosion, and flooding control.

Fig 2.3: Wet Pond ( Arika, Caleb and etall, Feb.2006)

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2.4.3.2Wetlands

In contrast to wet ponds, constructed wetlands are dominated by shallow

zones (less than 0.5). More vegetation can be incorporated into wetlands with the

associated potential for water quality enhancement. However, because of their

shallow depth, constructed wetlands are more land intensive than wet ponds and their

application to flood control is limited.

Fig 2.4: Stormwater Wetland [9]

2.4.3.3 Dry Ponds

A dry pond is a detention basin designed to temporarily store collected

stormwater runoff and release it at a controlled rate through an outlet. Dry ponds may

have a deep pool of water in the sediment forebay to reduce scour and resuspension

of sediment, but do not have a permanent pool of water in the main basin. This means

that there is no opportunity for settling of contaminants between storm events and

dilution of stormwater contaminants during storms. Therefore, although dry ponds

can be effective for erosion and flood control, they do not perform as well as wet

ponds for water quality control.

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Fig 2.5: Dry pond [10]

2.4.3.4 Infiltration Basins

Infiltration basins may be needed in some situations to provide adequate

groundwater recharge. However, water collected from a large area must infiltrate in a

relatively small area. This does not replicate natural conditions as well as lot-level

and conveyance infiltration controls. Infiltration basins can only be used where there

are soils through which water can rapidly flow. They are ineffective for flood control

because with larger water depths soil tends to be more compacted, allowing less

infiltration. Pretreatment of stormwater is required to prevent groundwater

contamination and clogging of soils.

Fig 2.6: Photograph of Constructed Infiltration Basin at the Pony Express Car

Wash in Oak Park Heights (Arika, Caleb and etall, Feb.2006)

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2.4.3.5 Filters

Filters are stormwater management practice use for water quality control by

filtering runoff through a bed of sand or other media. There are many types of filters.

They may be at the surface or underground, and the filter media may be sand and/or

organic material such as peat. Tilters can be incorporated into most parking lot areas

and commercial sites.

2.4.3.6 Vegetated Filter Strips

Vegetated filter strips (grass or forested) usually consist of a small dam and

planted vegetation. The dam is constructed perpendicular to the direction of flow and

ensures that the flow is spread evenly over the vegetation which filters out pollutants

and promotes stormwater infiltration. Vegetated filter strips can be used as infiltration

control, or a pretreatment control, and are best used adjacent to a buffer strip,

watercourse, or drainage swale.

Fig 2.7 Vegetated filter strip Photo by University of Illinois Extension. (Green,

C.H, USDA-ARS)

2.4.3.7 Grassed Swales

Grassed swales are typically shallow depressions several meters wide that

convey stormwater. The vegetation slows and filters stormwater. Dams can be

incorporated at intervals along swales to promote infiltration and settling of

25

contaminants. Ditches and culverts (swales separated by culverts at driveways) may

be used in residential areas as an effective alternative to curbs and gutters. (SMPD

Manual, 2003)

Fig 2.8: Photograph of grassed swale east of CR 13, Lake Elmo Dental clinic [11]

2.5 Important of Storm water Management.

Storm water management prevents physical damage to persons and property

from flooding, and also prevents polluted run-off from negatively impacting local

waterways. The installation of impervious surfaces interrupts the natural hydrologic

cycle, and causes less infiltration, interception, and evapotranspiration than was

present before any development occurred. Therefore, the volume and rate of flow of

storm water produced by the land surface have been greatly increased. The result of

this larger amount of storm water runoff significantly contributes to flooding,

sediment deposition, erosion, non-point source pollution and stream channel

instability.

Storm water should be considered a resource that provides benefits such as

groundwater recharge, which maintains flows in streams.

Storm water should be considered a resource that provides benefits such as

groundwater recharge, which maintains flows in streams.

Storm water management also reduces the frequency and severity of flooding.

Traditional storm water management takes surface runoff and diverts it to a

detention pond, which holds the water and releases it at a constant rate over time.

26

This approach allows the water to be returned to the watercourse at a high volume

over a longer period of time, which does not necessarily rectify the problem and may

actually create another. If storm water is recharged into the groundwater, it can

protect against erosion, flooding and water quality degradation. [12]

2.6 History

Historically, stormwater management focused on the prevention of flooding

and erosion in rivers and streams which receive stormwater. This reflected a societal

view of river channels as conduits for the convenient passage of stormwater. In order

to prevent flooding and erosion, agencies in urbanizing areas have taken drastic

actions over long periods of time. These have included channelizing rivers and

streams, building extensive flood protection works such as dams and energy

dissipaters, creating large detention ponds, and construction ever-large storm drain

systems to carry stormwater away from human- built impervious landscapes and into

rivers. Unfortunately, such approaches to stormwater management have had a

number of unintended side effects including the destruction of aquatic habitats, the

diminishment of aquatic communities, the degradation of surface and groundwater

quality, channel instability and the depletion of groundwater.

Today, when designing stormwater management facilities, specialists

recognize the importance of maintaining and enhancing surface and groundwater

systems in a manner that as closely as possible resembles ‘natural’ form and function.

Instead of conveying all stormwater into storm drains, designers consider facilities

that allow infiltration of stormwater to recharge groundwater and maintain base flows

of rivers. Instead of turning rivers into concrete channels to carry stormwater,

designers are re-naturalizing channels to increase riparian cover and to create stable,

self-maintaining forms. Instead of considering rivers as conduits of stormwater,

designers are considering them as complex, self-regulating systems and important

habitats for invertebrates, fish, birds, reptiles and amphibians. In short modern water

resource management try to maintain healthy river systems. In such systems, a river’s

energy is naturally dissipated through balanced rates of erosion and sediment

27

transport. When erosion and sediment transport occur at natural rates, a variety of

aquatic habitats are supported and channel morphology is preserved. [13]

2.7 Discharge measurement methods:

2.7.1 Anderson Method

The Anderson Method was developed by the United States Geological Service

(USGS) in 1968 to evaluate the effects of urban development on floods in Northern

Virginia. Further discussion can be found in the publication “Effects of Urban

Development on floods in Northern Virginia” by Daniel G. Anderson, U.S.G.S.

Water Resources Division 1968.

One of the advantages of the Anderson Method is that the lag time (T) can be

easily calculated for drainage basins that fit the description for one of the three

scenarios given:

1) Natural rural basin

2) Developed basin partly channeled or

3) Completely developed and sewered basin.

For basins that are partly developed, there is no direct method provided to

calculate lag time. The following explanation of lag time is reproduced from the

original report to provide the user with information to properly assess lag time for use

in the Anderson Method based upon the parameters used in the study.

This method was developed from analysis of drainage basins in Northern

Virginia with drainage area sizes up to 570 square miles.

The equation for Anderson method is given asQ = R (230) × K × A . T .Where

28

= Maximum rate of runoff (cfs)

= Flood frequency ration

K = Coefficient of imperviousness (obtained from equation 3.3)

A = Catchment area (sq. mile)

T = Time lag (hrs.) table 3.2

2.7.2 Snyder Method

The Snyder Method was developed as the “Synthetic Flood Frequency

Method” by Franklin F. Snyder. This was originally presented in the ASCE

Processdings, Vol.84No.HYS in October 1958. The Snyder Method has been found

to produce acceptable results when properly applied to drainage areas between 200

acres and 20 square miles. This method provides the user with an adjustment factor

for partly developed basins by the use of percentage factors for the length of channel

storm sewered and/ or improved.

The equation for Snyder method is given as

= 500AIR

Where

= Peak discharge (cfs)

A = Catchment area (sq. Mile)

IR = (in/hr.)

= Time of concentration (hrs.)

29

2.7.3 Regression Method

Regional regression equations are a commonly accepted method for

estimating peak flows at ungagged sites or sites with insufficient data. Also, they

have been shown to be accurate, reliable, and easy to use as well as providing

consistent findings when applied by different hydraulic engineers (Newton and

Herrin, 1982). Regression studies are statistical practices used to develop runoff

equations. These equations are used to relate such things are the peak flowor some

other flood characteristics at a specified recurrence interval to the watershed’s

physiographic, hydrologic and meteorologic characteristics.

Rural regression method procedure is presented in the urban regression

method procedure and the procedure of urban regression method is not intended to

require measurement. A certain amount of subjectivity is involved, and field checking

should be performed to obtain the best estimate. Then BDF is the sum of the four

assigned codes, and the maximum value for a fully developed drainage system would

be 12. Conversely, a totally undeveloped drainage system would receive a BDF of

zero (0). In fact basin could be partially urbanized, have some impervious area, and

have some improvement of secondary tributaries, and still have an assigned BFD of

zero (0).

The regression equation should be used routinely in design for drainage areas

greater than one square mile.

The equation of both the method are given bellow

Rural regression method

R = C

Where

R = Peak discharge for the rural watershed for recurrence interval T ( cfs)

C = Regression contestant (dimension less)

30

A = Contributing drainage area (sq. mille )

B = Regression exponent

Urban regression method

U = C (13 − ) R

Where

U = Peak discharge for the urban watershed for recurrence interval T (cfs)

C = Regression constant (dimension less)

A = Contributing drainage area (sq. mille)

BDF = Basin Development Factor (dimension less)

R = Peak discharge for an equivalent rural drainage basin in the same hydrologic

area as the urban basin and for recurrence interval T, ( cfs)

B1,b2,b3 = Regression exponents

(Drainage Manual, April 2002). [14]

31

CHAPTER 3

MATERIALS AND METHODS

3.1 Site

The proposed RLHS is located on Nasir Bagh Road approximately 5 Km from

Jamrud Road. The proposed Hosing Scheme spreads on 4054.2 ac and consists of 5

zones. After complete development approximately 60% pervious area will be

converted to impervious area. The goal of this study is evaluate the effect of RLHS on

future flood in Takhta Beg Khawar.

3.2 Research Parameters

3.2.1 Catchment area

An area characterized by all direct runoff being conveyed to the same outlet is

called catchment area. Similar terms include basin, sub watershed, drainage basin,

watershed and catch basin. The catchment area of Takhta Beg Khawar at RLHS is

4104.4 ac provided by Peshawar Development Authority.

3.2.2 Impervious surface

Impervious surfaces consist of roads, sidewalks, driveways, parking lots and

roof tops. The estimated impervious area of proposed RLHS is 2524.20 ac which

consist of roads, roof tops and sidewalks etc.

3.2.3 Time lag

The time from the center of mass of excess rainfall to the hydrograph peak.

Lag time is also referred to as basin lag. The estimated Time lag is calculated by

formulas from table (3.2)

32

3.2.4 Time of concentration

The travel time from the hydraulically furthermost point in a watershed to the

outlet. This is also defined as time from the end of rainfall excess to the recession

curve inflection. The estimated Time of concentration is given by equation (3.9)

3.2.5 Length of main stream

The length of longest stream from the start to the end of an outlet of

catchment area is the Length of main stream. We calculated this with the help of

ArcGIS. It is 5.0747 mile.

3.2.6 Slope

It is the ratio of difference in Elevations at 85% and 10% (1341.86 −1138.45)of the length of main stream to the difference in lengths at 85% and 10%

(4.3135 − 0.50747) of length of main stream. We calculated these with the help of

ArcGIS. The value is 53.44 ft/mile.

3.3 Methodology

3.3.1 Anderson method

The equation for Anderson method is given asQ = R (230) K A0.82T−0.48 (3.1)

WhereQ = Maximum rate of runoff (cfs)R = Flood frequency ration

K = Coefficient of imperviousness (obtained from equation 3.3)

A = Catchment area (sq. mile)

33

T = Time lag (hrs.) table 3.2

Table: 3.1 calculated data

Catchment Area 6.413 sq. mile

Total Area of Regi. 4054.2059 acres

Length of the main stream 5.075 mile

Elev. At 10% of length 1138.45 ft.

Elev. At 85% of length 1341.86 ft.

10% of length 0.50747 mile

85% of length 4.3135 mile

Impervious Area of Regi. 2524.2059 acres

Slope =( . . )( ) (3.2)

=( . . )( . .

= 53.44 ft. /mile

Table: 3.2 Anderson Time Lag computations

Time Lag, T Watershed Description4.64 L√S . For Natural Rural Watershed

0.90 L√S . For Developed watershed partially channelized

0.56 L√S . For Completely Developed and Sewered Watershed

34

Estimation of discharge before development

T = 464 .(3.3)

Where

T = Time lag (hour)

L = Length of the main stream (mile)

S = Slope (ft./mile)

T = 4.64 .√ . .= 3.98 hrs.

Existing Impervious area = l = 4%

K = 1+0.015×l (3.4)

Where

K = Coefficient of imperviousness

l = percentage of imperviousness

K = 1+ 0.015×4

K = 1.06

35

Table: 3.3 Anderson Flood Frequency Ratios

F 2.33 5 10 25 50 100

Rn 1.00 1.65 2.20 3.30 4.40 5.50

R100 1.00 1.24 1.45 1.80 2.00 2.20

=. × ( . × )

(3.5)

Where

Rf = Flood frequency ratio for flood frequency “f” based on percentages of

imperviousness from 0 to 100%

=. . × ( . × . . ).

= 2.129

= 2.129× (230) ×1.06× (6.413) . (3.98) .= 1228 cfs.

=. . × ( . × . . ).

= 5.18868

= 5.18868× (230) × 1.06 × (6.413) . (3.98) .= 2991.83 cfs.

36

Estimation of discharge after development

Other parameters will remain unchanged only impervious area and Time lag will

change after development.

l = × 100 (3.6)

=. . × 100

= 62.26 %

T = 0.56 √ .(3.7)

= 0.56.√ . .

= 0.463 hrs.

K = 1 + 0.015 ×l

= 1.934

=. × ( . × – )

=. × . ( . × ).

= 1

= R2 × (230) ×K×( ) . ( ) .= 1× (230) ×1.934×(6.413) . (0.463) .

37

= 2954 cfs

=. . × . ( . × . . ).

= 1.596

= 1.596× (230) ×1.934×(6.413) . (0.463) .= 4716 cfs

=. . × . ×( . × . . ).

= 2.844

= 2.844 × (230) ×1.934 ×(6.413) . (0.463) .= 8403 cfs

3.3.2 Snyder Method

The equation for Snyder method is given as

= 500AIR (3.8)

Where

= Peak discharge (cfs)

A = Catchment area (sq. Mile)

IR = (in/hr.)

Tc = Time of concentration (hrs.)

38

Table 3.4: Calculated data

Catchment Area 6.413 sq. mile

Length of Main Stream 5.0747 mile

Elev. At the Upper End 1391.076 ft.

Elev. At the Down End 1122.047 ft.

Ct = Adjustment factor defined by the development condition of the drainage area

Table 3.5: Ct Values for the Snyder Method

Type of Areas Ct, Hours/mile

Natural Basins 1.7

Overland Flow 0.85

Sewered Areas 0.42

= × L (3.9)

L = Equivalent length of channel with slope of 1% and friction factor equal to 0.1

and defined by the following equation

L =× ×√ (3.10)

Where

L = Length of main stream

n = Roughness coefficient

S = Weighted slope of the channel

39

S = 39 (3.11)

Mean height of elevation =. .

(3.12)

=. .

= 134.51

S = 26.51 = 1% According to L description

L =× . × .√

= 2.03

Discharge estimation before development

Tc = Ct L

Where

Tc = Time of concentration

Ct = Adjusted factor

L = Equivalent length.

Tc = 1.7 × 2.03

= 3.451 hrs.

Ct value is taken from the table which before development is Ct = 1.7 hr./mile

From the rainfall data we use the 3.5 inches rainfall for 10-year discharge and 8

inches for the 100- year discharge. For runoff calculations for 10 and 100 –years

discharge we use the graphs given in Appendix.

Rainfall for 10-year return period = 88 mm = 3.5 inch

40

Rainfall for 100-year return period = 204 mm = 8 inch

From the graphs we have the following data

The impervious area before the Regi lalma housing scheme is 4%

Natural runoff for 10-year = 38%

Natural runoff for 100-year = 64%

Adjusted runoff for 10-year = 40%

Adjusted runoff for 100-year = 64%

Table 3.6: Discharges before development

Frequency (years) 10-year 100-year

Rainfall (inch) 3.5 inch 8 inch

Percentage of Natural runoff

(%)

38% 64%

Percentage runoff adjusted

(%)

0.4 0.64

Runoff (runoff adjusted ×

rainfall)

1.4 in/hr 5.12 in/hr

Ir = runoff/Tc 0.406 1.484

Q = 500×A×(Ir) 1301 cfs 4758 cfs

Discharge estimation after development

Ct = it is selected from the table 3.6

Ct = 0.42

41

Percentage of impervious area =

= . ×100

= 62.26 %

Tc = Ct × L

= 0.42 × 2.03

= 0.853 hrs.

Natural runoff for 10-year = 38 %

Natural runoff for 100-year = 64 %

Adjusted runoff for 10-year =75%

Adjusted runoff for 100-year = 86%

Table 3.7: Discharges after development

Frequency (year) 10-year 100-year

Rainfall (inch) 3.5 in 8 in

Percentage of Natural runoff

(%)

38% 64%

Percentage runoff adjusted (%) 0.75 0.86

Runoff (runoff adjusted ×

rainfall)

2.625 6.88

Ir = (runoff/Tc) 3.079 in/hr 8.07 in/hr

Q = 500× A × (Ir) 9873 cfs 25876 cfs

42

3.3.3 Regression Method

According to Rural Regression Method the discharge for the 10-year and 100-

year is given below

For 10 –year

Q10 = 372 × .= 372× 6.413 .= 1287.241(cfs)

For 100-year

Q100 = 1254 × .= 1254 × 6.413 .

= 3583.333 (cfs)

Urban regression method

After development

Table 3.8: Proposed Condition of BDF

Section A B C

Storm drain 1 1 1

Channel improvement 0 0 1

Impervious channel

lignin

0 1 1

Crub and gutter 0 1 1

Total of all 1 3 4

Total BDF 8

43

For 10-year frequency

Q10 = 9.51 × (1) . (13 − 8) . (1287.241) .= 2052.64 (cfs)

For 100-year frequency

Q100 = 7.7 × (1) . (13 − 8) . (3583.333) .= 4993.38 (cfs)

Table 3.9 Result of different methods before and after development

Methods Before development After development

10-years 100-years 10-years 100-years

Anderson 1228 (cfs) 2991.83 (cfs) 4716 (cfs) 8403 (cfs)

Snyder 1301 (cfs) 4758 (cfs) 9873 (cfs) 25876 (cfs)

Regression 1287.241 (cfs) 3583.333 (cfs) 2052.64 (cfs) 4993.38 (cfs)

44

CHAPTER 4

RESULTS AND DISCUSSION

For our calculation we considering two conditions of Regi lalma, one is before

the development as rural area and other after the development when complete

development of Regi lalma housing scheme will occur as urban area.

Table 4.1: Results of different methods before and after development

Methods Before development After development

10-years 100-years 10-years 100-years

Anderson 1228 (cfs) 2991.83 (cfs) 4716 (cfs) 8403 (cfs)

Snyder 1301 (cfs) 4758 (cfs) 9873 (cfs) 25876 (cfs)

Regression 1287.241 (cfs) 3583.333 (cfs) 2052.64 (cfs) 4993.38 (cfs)

In every method either it is Anderson, Snyder or Regression the discharge

after the development is grater then the discharge before the development. The reason

is that Regi lalma was a rural area and mostly consist of bare soil, natural detention

ditches, tress and grasses, so when there was rainfall most of the rainwater directly

infiltrated into the soil, part of that rainfall water stored in the natural detention basin

and some friction of rainwater absorbed by trees and grasses. The soil surface was

rough and there was less chance for rainwater to accumulate quickly and cause peak

discharge in nearby creek named Takhta Beg Khwar.

The discharge after the development is greater because after completion of

Regi lalma housing scheme the permeable soil will be replaced by the impermeable

soil cover such as construction of roads, buildings, parking lots and pavements and

due to which the infiltration rate of rainwater into the soil will be reduce, less water

will be store on the soil surface due to elimination of natural detention ditches and no

water will be absorb by the trees and grass due to deforestation. The water will

accumulated on the soil surface causing larger volume of runoff water which will

45

quickly join the nearby Takhta Beg Khwar. The drainage drains will reduce the time

for the runoff water to reach the stream.

46

CHAPTER 5

CONCLUSION AND RECOMMENDATION

5.1 Conclusion

It concluded from this study that as the urbanization is increasing the risk of

flood is also increasing, because with urbanization more and more permeable soil is

converted into the impervious cover which infiltrate less water into the soil as a result

the groundwater recharge is less and more water is accumulated on the surface which

started runoff, the impervious surfaces and compacted soils, as well as improvements

to the drainage system such as storm drains, pipes and ditches increase the velocity of

runoff and reduce the Time of concentration causing peak discharge in the nearby

stream and floods in the downside.

5.2 Recommendation

Based on the results of this study. It is believed that urbanization of RLHS will

increase peak discharge in Takhta Beg Khawar. Therefore the following control

(mitigation) measures are recommended for RLHS.

5.2.3 Storage Controls

Rooftop storage

Parking lot storage

Super pipe (oversized storm sewer) storage

Rear yard storage

5.2.2 Infiltration controls

Reduced lot grading

Rear yard soakaway pits

Infiltration trenches

47

Pervious pipe systems

Grassed swales

Vegetated filter strips

5.2.3 End-of-pipe Controls

Dry ponds

Wet ponds

Wetlands

Filters

Infiltration basins

48

References:

[1] Pollution, committee on reducing Storm water Discharge contributions to water.

Urban Storm water Management in the United States. Washington, DC: The National

Accedemic Press, 2008.

-.Urban Storm water Management in the United States—2008,

http://www.nap.edu.openbook.php?record_id=12465&=IR(Accessed June 22, 2012).

[2] Ruby, Emily. “How Urbanization Affects the Water Cycle”. ---, California: --

RUPY EMILY,-- www.coastal.ca.gov/nps/watercyclefacts.pdf (accessed JUNE 22,

2012).

[3] P. Konrad. Christopher.(USGS) “Effects of Urban Development on Floods”.

pubs.usgs.gov/fs/fs07603/.

[4] http://www.huffingtonpost.com/asif-iqbal/sustainable-cities-in-pak_b_1400446.html

Accessed time 10:13 pm and date 6/26/2012

[5] http://www.unescap.org/idd/events/2009_EGM-DRR/SAARC-India-Shankar-

Mahto-Urban-Flood-Mgt-Final.pdf . (9:35 pm) (22/6/2012)

[6] Georgia storm water management manual volume 1: Stormwater Policy

Guidebook First Edition – August 2001

[7] Stormwater Management Handbook by Pocono Northeast resource conservation

and development Council.

http://wren.palwv.org/products/documents/RCDStormwaterHandbook_000.pdf

Accessed time (7:30 pm) and date (22/6/2012)

[8] Farhad Abdolian in general middle east posted Feb. 18th 2008

49

[9] www.dcr.virginia.gov/stormwater_management/documents/Chapter_3-09.pdf.

Accessed time 5:56pm and 6/26/2012

[10] http://cfpub.epa.gov/npdes/images/menuofbmps/drypondpic.png Accessed

time2:15 pm. And date 6/26/2012.

[11] The storm management planning and design manual, 2003 is available on the

ministry on environments (MOE) website at: http://www.enc.gov.on.ca.

[12] Arika, caleb, Dario canelon, John Nieber, Feb. 2006, Impact of Alternative

Storm water management Approaches on Highway Infrastructure: project Task

Reports- volume 2. Published by Minnesota Department of Transportation Research

Services section. http://www.lrrb.org/PDF/200549B.pdf

[13] Storm water management guidelines, Our member municipalities may

1996.Credit Valley Conservation. http://mississauga.com/conservation.html

[14] Drainage Manual prepared by location and design division hydraulics section

April 2002 Virginia department of transportation.

50