A GIS Based Approach to Siting Stormwater Detention Ponds in the City of Guelph

Stormwater detention ponds have become an increasingly important part of best management practices in stormwater management. Demands on stormwater management are currently greater than ever, as expanding urbanized areas and their impervious surfaces are resulting in higher volumes of runoff. Stormwater runoff is a major concern because it carries pollutants, debris, and other environmentally degrading by-products of urban areas. The city of Guelph is currently experiencing an expansion in its southern urban limits. As a result, this hydrology based study has used this region as the area of interest due to the need for stormwater management. Southern Guelph and its surrounding subcatchments of concern were subject to analysis by using a multi-criteria evaluation model in order to find the most suitable sites for stormwater detention ponds. This model was developed and applied in a geographic information systems tool, ArcMap 10. The multi-criteria evaluation model developed for this study incorporated both anthropogenic and natural factors. These factors included the distance to commercial and industrial built-up land, distance to residential built-up land, distance to agricultural land, slope, soil class, depth to water table, distance to wetlands, and flow accumulation. These factor layers were then applied to four different scenarios, which included a basic scenario, environmental scenario, economic scenario, and control scenario. Each factor layer was allocated an input weight for each scenario based on a pairwise ranking scale of importance. Each scenario was run in the multi-criteria evaluation model and produced an output raster dataset that indicated potential detention pond sites within a range of suitability scores. The basic and environmental scenarios indicated the same 0.0027 km² site as most suitable, with a percent suitability of 80.61 in the environmental scenario, and 80.12 in the basic scenario. The economic scenario indicated a 0.0009 km² site with a suitability score of 81 percent. The economic scenario and environmental scenario were then most critically analyzed in this study, as their siting results were compared and contrasted. The findings of this study have indicated that the combination of various data sets in a GIS tool can be combined and processed in order to display and analyze the spatial variability of potential sites for stormwater detention ponds.