Maintaining Ecohydrological Sustainability of

Alberta’s Urban Natural Areas Adjacent to

Proposed Residential Developments

Water Tech 2017, Banff, AB

Urban Analysis, City Planning | April 2017

Presented by Achyut Adhikari and Rudy Maji

Outline

• Wetland Policy and Planning Process

• Project Background

• Study Objectives

• Screening Level Integrated SW/GW Numerical Modelling

• Study Findings

• Summary and Recommendations.

Urban Analysis, City Planning | April 2017

Wetland Policy and Implementation

Parks + Biodiversity, City Planning | April 2016Urban Analysis, City Planning | April 2017

City’s Ecological NetworkBig Lake and Lois Hole Centennial Provincial Park is a vital part of Edmonton’s ecological network and contribute to the City’s multifunctional green network

Background

Big Lake and Lois Hole Centennial Provincial

Park

• Globally Significant Habitat for Waterfowl

Habitat support local, regional and global

biodiversity

Kinglet Garden Natural Areas

• Part of Regional Biodiversity Core Area

connected both ecologically and hydrologically

to Big Lake and LHCPP

• Habitat Features: Wetland(marsh, fen),

Natural drainage channel, Forested tree

stands

Urban Analysis, City Planning | April 2017

Background

Wetland Fen

Neighbourhood 5 Neighbourhood 4

Can we sustain the structure and function of natural features in Kinglet Garden Natural Area following proposed urban development?

Urban Analysis, City Planning | April 2017

Study Objectives

Parks + Biodiversity, City Planning | April 2016

• How would the proposed development impact the existing

hydrological interaction (surface water and ground water) of the

Kinglet Gardens NA and Lois Hole Centennial Provincial Park?

(Supplemented Information required for approval of NSP)

Urban Analysis, City Planning | April 2017

Integrated Surface Water-Groundwater Model for

• Channel Capacity and Discharge rate Assessment

• Proposed SWMF and Outfall Evaluation

• Water Quality including Isotope Analysis

• Develop Scenarios to understand the impact of post

development hydrology in natural area sustainability

Conditions that Impact Natural Area,

Wetlands and Fen Sustainability

Hydrological/Hydrogeological Aspects:

Change in surface water and groundwater catchments;

Water level changes/fluctuation;

Surface flooding depth and duration;

Water quality changes due to reduced GW recharge.

Risk tolerance of sensitive species

Social Context:

An increase in domestic pets and human using the area;

An increase in light and noise pollution;

An increase in trampling and/or plant collection; and

The introduction of invasive species from gardens.

April 5, 2017 8

(Ref: Toronto and Region Conservation Authority, 2011)

Integrated SW-GW Model: Approach

Data Synthesis;

Conceptual Modelling;

Numerical Model Development;

Numerical Model Calibration; and

Forecast Models:

Pre-Development Scenario;

Long-Term Annual Average Surplus Input;

Monthly Average Surplus Inputs; and

Extreme Event (100-year 4-Hour Storm Event).

Post-Development Scenario;

Long-Term Annual Average Surplus Input;

Monthly Average Surplus Inputs; and

Extreme Event (100-year 4-Hour Storm Event) Precipitation Input.

April 5, 2017 9

Topography and Drainage

April 5, 2017 10

Elevations

(masl)

Villeneuve

St.

Albert

Big

Lake

Local Study Area

LiDAR Topo

April 5, 2017 11

Hydrologic Cycle

April 5, 2017 12

Reference: Jyrkama (2003)

Precipitation (P) = Evapotranspiration (ET) + Runoff (R) + Groundwater Infiltration (I)

P – ET = R + I

Surplus (S) = R + I

Conceptual Hydrostratigraphic Layering

April 5, 2017 13

Upper 5 m to 7 m (approximately) is

clay mixed with silt and sand; and

Sand and silty sand unit is

approximately 5 m to 10 m thick.

Hydrostratigraphic Cross-Section

April 5, 2017 14

West East

North South Key Map

5x10-7 m/s

5x10-5 m/s

1x10-7 m/s

1x10-9 m/s.

Soil Conductivities

Integrated SW-GW Model: Finite Element

Mesh

April 5, 2017 15

Model Construction Summary

HydroGeoSphere was used

Model Domain Area: 670.5 sq. km;

Nodal spacing:

Regional: 100 m to 200 m;

Study Area: 10 m to 20 m;

Number of numerical layers: 16;

Number of nodes per layer: 55,405;

Total number of nodes: 886,480;

Hydrostratigraphy:

Clay Till;

Sand/Silty Sand;

Till; and

Bedrock.

April 5, 2017 16

Monitoring Well Locations and Hydraulic

Head Calibration Plot

April 5, 2017 17

Simulated Steady-State Flow

April 5, 2017 18

Total Inflow = Surplus Water Applied on the Model Domain + Flow at Villeneuve = Total Outflow (i.e., Flow at St. Albert)

Model Calibration:

Simulated Surface Water Features

April 5, 2017 19

Note: Surface water features are not defined a priori, but arise as a consequence of applied water flows, topography and surface and subsurface properties.

Big Lake Horseshoe

Lake

Model Calibration:

Simulated vs. Observed Streamflow (St. Albert)

April 5, 2017 20

Area (km2)

Annual Surplus

(mm/y)

D/S 2590.9 33.33

U/S 1889.5 30.55

Model Domain 670.454 42.70

Simulation Cases and Scenarios

Forecast Models;

Pre-Development Scenario;

Long-Term Annual Average Surplus Input;

Monthly Average Surplus Input;

Extreme Event (100-year 4-Hour Storm Event) Precipitation Input;

Post-Development Scenario;

Long-Term Annual Average Input;

Monthly Average Surplus Input;

Extreme Event (100-year 4-Hour Storm Event) Precipitation Input.

April 5, 2017 21

Key Assumptions

ET processes were not simulated (i.e., Pre- and Post-Development ET

losses were assumed to be the same);

Snow-melt, Soil Freeze/Thaw processes were not simulated;

Post-Development Runoff Coefficient: 0.65;

Maximum Allowable discharge rate for each SWMF is 2.5 L/s/Ha and

has sufficient capacity to hold excess stormwater prior to discharge.

April 5, 2017 22

SWMF Outfall Locations

April 5, 2017 23

Groundwater Drawdown (Monthly Surplus

Input)

April 5, 2017 24

December July

Conceptual Flow Regime

April 5, 2017 25

Adapted from DFO (1994)

Post Development

Flows with SWMF

(Traditional)

Longer Duration of

Peak Flows

Post Development

Flows with SWMF

(Leaky)

Pre- and Post Development Hydrographs

(100-Year 4-Hour Storm Event)

April 5, 2017 26

The image to the right shows the pre-

development (solid lines) and post-

development (dashed lines) hydrographs

downstream of the SWMF outfalls.

The image below shows the outfall (blue

circles) and hydrograph (blue lines) locations,

as well as the stormbasin boundary (red line).

H9PD1

PD2

PD3

Surface Water Depth Difference (100-Year 4-

Hour Storm Event)

April 5, 2017 27

O6

Pre-and post development surface

water depth in wetland at observation

point O6 (shown below).

Stormwater pond causes early arrival

of storm pulse, smaller peak and

extended tailing of late-time

responses.

Study Findings

Three assessment metrics were evaluated in support of natural area sustainability:

Pre- to Post-Development water balance;

Pre- to Post-Development groundwater level change; and

Peak flow and surface inundation duration.

Numerical model findings in terms of the above performance metrics:

Pre- to Post-Development surface water depth change is negligible (mm scale).

However, streamflow at certain locations increases due to SWMF outfalls and

presence of clay/clay-till;

Simulation results indicate the change in groundwater table depth would be in the

range from -0.5 m to +2 m at Post-Development conditions; and

Post-Development streamflow duration was simulated to be longer compared to the

Pre-Development conditions.

April 5, 2017 28

What the Study Findings Mean in the Context

of Ecology?

Fen or Bog might disappear due to prolonged period of inundation

The vegetation pattern could change to degraded marsh;

April 5, 2017 29

Design Inputs

Numerical Model Results – a few design inputs:

Sub-surface geology is key to control the water levels, flows and

infiltration for the Pre- and Post-Development conditions;

Runoff coefficient of 0.65 might be low for designing the SWMFs,

given the surficial geology of proposed neighbourhood areas

consists of clay/clay till with traces of sand/silt that inhibits infiltration

and promotes surface runoff; and

Low-impact development involving more green spaces and ‘leaky’

stormwater ponds in conjunction with adaptive wetlands monitoring.

April 5, 2017 30

Summary and Recommendations

Provided a road map to protect the long-term interests of Albertans,

including people who live in the North Saskatchewan River watershed,

by promoting wetland conservation, protection and sustainable

management as per the existing policies (COE 2012, Alberta

Government 2013).

The work was used to aid in developing mitigation measures to reduce

impacts on the wetlands, while sustaining municipal growth.

The traditional residential development and stormwater pond design

were found to cause adverse wetland changes. Golder’s solutions

recommended low-impact development involving more green spaces

and ‘leaky’ stormwater ponds in conjunction with adaptive wetlands

monitoring.

April 5, 2017 31

Key Contributors

Achyut Adhikari (Client, City of Edmonton)

Golder Project Team

Paul Morton (Project Manager and Hydrogeologist);

Rudy Maji (Modelling Lead);

Rob McLaren (Lead HGS Modeller);

Julien Lacrampe (Surface Water Lead); and

Matt Neuner (Water Quality Lead).

April 5, 2017 32