Hydrologic Modelling For Natural Area Management
When new neighbourhoods are built within the City of Edmonton, a portion of the existing natural areas are protected and maintained as part of the City’s ecological network. To ensure that these important urban spaces are properly managed, the City requires that all natural areas retained within a new municipal development receive a Site-Specific Natural Area Management Plan (SSNAMP). These comprehensive plans provide guidance on the unique features and management strategies that are applicable to the site and also ensure the long-term sustainability of the natural area.
Fiera Biological recently completed SSNAMPs on behalf of an Edmonton developer for two natural areas being retained within Marquis, a new neighbourhood in northeast Edmonton. Each of these natural areas contains a wetland; post-development changes to the wetlands’ catchment areas and land use, as well as to the location of the wetland overflow, will alter the amount of water each wetland will receive and store. It was therefore important for Fiera Biological to demonstrate to the City that the wetlands would neither dry up nor flood the surrounding area in the new urbanized landscape.
To do so, we modelled the pre- and post-development monthly water balance for each wetland. Water balance models estimate the volume of water held within a basin based on hydrologic inputs (storage, precipitation, and runoff) and outputs (evapotranspiration, groundwater outflow, and surface overflow to ditches). Climate data from normal, wet, and dry years were used to model how the basin volume in each wetland may change throughout the year under different climatic conditions. By understanding the current, pre-development water balance, we can see the impacts that the proposed development may have on water levels within the wetlands. Fiera Biological was able to work with our client to ensure that the proposed site design would supply an adequate volume of water to the wetland, and that berms and/or overflows could be put in appropriate locations and heights to ensure that stormwater would not negatively impact nearby infrastructure. As a result, Fiera Biological was able to demonstrate in the SSNAMPs that, post-development, these wetlands will neither dry up during dry years, nor threaten nearby infrastructure during high volume runoff events. Additionally, the wetlands will continue to experience seasonal drawdown, an important aspect of the marsh hydroperiod.
In addition to this hydrologic modelling, Fiera Biological also proposed opportunities for restoration, including weed removal and planting native riparian plant species in the buffer surrounding the wetlands, which are currently agricultural crops. These will enhance the habitat for wetland species. Additionally, the management plans provided construction mitigation measures for the developer to minimize impacts to the wetlands during construction, and they outlined the operational guidelines for the City of Edmonton, ensuring that the long-term health of the natural areas will be monitored. The City of Edmonton will use these plans to ensure these natural areas will be well-managed and sustainable for years to come.
Key Personnel / Role:
Erin Doxsey-Whitfield / GIS Specialist and Hydrologist
Shari Clare / Wetland Ecology, Wetland Management, Policy, Project Management
Urban Land Developer
September to December, 2016