Maintaining Ecohydrological Sustainability of Alberta s Urban Natural Areas Adjacent to Proposed Residential Developments

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1 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

2 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

3 Wetland Policy and Implementation Parks + Biodiversity, City Planning April 2016 Urban Analysis, City Planning April 2017

4 City s Ecological Network Big 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

5 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

6 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

7 Study Objectives 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) 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 Parks + Biodiversity, City Planning April 2016 Urban Analysis, City Planning April 2017

8 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. (Ref: Toronto and Region Conservation Authority, 2011) April 5,

9 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,

10 Topography and Drainage Elevations (masl) Villeneuve St. Albert Big Lake Local Study Area April 5,

11 LiDAR Topo April 5,

12 Hydrologic Cycle Precipitation (P) = Evapotranspiration (ET) + Runoff (R) + Groundwater Infiltration (I) P ET = R + I Surplus (S) = R + I Reference: Jyrkama (2003) April 5,

13 Conceptual Hydrostratigraphic Layering 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. April 5,

14 Hydrostratigraphic Cross-Section North South Key Map West East Soil Conductivities 5x10-7 m/s 5x10-5 m/s 1x10-7 m/s 1x10-9 m/s. April 5,

15 Integrated SW-GW Model: Finite Element Mesh April 5,

16 Model Construction Summary HydroGeoSphere was used Model Domain Area: 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,

17 Monitoring Well Locations and Hydraulic Head Calibration Plot April 5,

18 Simulated Steady-State Flow Total Inflow = Surplus Water Applied on the Model Domain + Flow at Villeneuve = Total Outflow (i.e., Flow at St. Albert) April 5,

19 Model Calibration: Simulated Surface Water Features Big Lake Horseshoe Lake Note: Surface water features are not defined a priori, but arise as a consequence of applied water flows, topography and surface and subsurface properties. April 5,

20 Model Calibration: Simulated vs. Observed Streamflow (St. Albert) Area (km2) Annual Surplus (mm/y) D/S U/S Model Domain April 5,

21 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,

22 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,

23 SWMF Outfall Locations April 5,

24 Groundwater Drawdown (Monthly Surplus Input) December July April 5,

25 Conceptual Flow Regime Longer Duration of Peak Flows Post Development Flows with SWMF (Leaky) Post Development Flows with SWMF (Traditional) Adapted from DFO (1994) April 5,

26 Pre- and Post Development Hydrographs (100-Year 4-Hour Storm Event) The image to the right shows the predevelopment (solid lines) and postdevelopment (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). H9 PD1 PD2 PD3 April 5,

27 Surface Water Depth Difference (100-Year 4- Hour Storm Event) 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. O6 April 5,

28 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,

29 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,

30 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,

31 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,

32 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,