Merchant, M., Wilcox, B.

The study area is the city of Guelph (43°33'N 80°15'W), located in southwestern Ontario with a total land area of 86.72 square kilometers (Statistics Canada). Guelph is in close proximity to several other major southern Ontario cities and municipalities (Figure 5). It is approximately 28 kilometers from Waterloo, 43 kilometers from Hamilton, 100 kilometers from Toronto, and 50 kilometers to the nearest Great Lake, Lake Ontario. Guelph is also situated in the Grand River watershed (Figure 6). The Grand River watershed is the largest watershed in southern Ontario, measuring 6,800 square kilometers (GRCA, 2012). The Grand River flows through the watershed with a total length of 300 kilometers, beginning in the highlands of Dufferin County and flowing to Port Maitland on Lake Erie (GRCA, 2012).

Guelph was selected as the study site based on two criteria. First, the city of Guelph is experiencing population growth and urban expansion. The population of Guelph circa 2006 was 114,943, resulting in a population density per square kilometer of 1,325.5 (Statistics Canada). The city of Guelph experienced an 8.3% increase in population from the years 2001 - 2006, thus illustrating the city's expansion, which has caused urban sprawl to occur (Statistics Canada). This criterion is also important because of the impact it has on Guelph's plans for urban expansion in the city's southern end. The second criterion is that Guelph is already a region that uses structural BMP facilities within its boundaries. The City of Guelph's Stormwater Management (SWM) Master plan states that its long term plan will integrate flood control and stormwater drainage with opportunities to improve and protect groundwater and surface water quality (City of Guelph, 2012). Included in the city's SWM master plan is the use of structural BMP facilities, and the specifications that they must meet. In most cases, municipalities use stormwater management strategies that include detention ponds because they are facing the need to reduce flooding impacts from new developments or because local stream segments are not meeting water quality standards (Debo & Reese, 2003).

The South Guelph District Centre (SGDC), a currently urbanizing area that will be used as an important subset of the study area, is an example of development in the southern end of Guelph that is scheduled to be built at the intersection of two main arterial roads, Gordon Street and Clair Road (Figure 7). Gordon Street is a major gateway road to the city of Guelph from Highway 401, and thus has a high level of visibility and accessibility (City of Guelph, 2012). The city of Guelph has outlined objectives for the development center which include providing a range of mixed land uses to serve the growing south Guelph community, to incorporate a high standard of building and landscape design, and to provide an aesthetic urban parkway or gateway (City of Guelph, 2012). The combined outcome of these objectives will produce an area with low rates of infiltration, which will cause major hydrological changes that require management.

There are five subcatchments in the Grand River watershed that will experience considerable environmental impacts from the southern urban limits of Guelph and the proposed areas of development. As a result, this study has based its results on siting detention ponds within these five subcatchments that have a combined area of 151.88 km² (Figure 8). The study area is composed of several different land use types. These include 5.04 km² of residential built up land (3.3% of the study area), 9.47 km² of commercial and industrial built up land (6.2% of the study area), and 81.38 km² of agricultural land (53.6% of the study area) (Figure 9; Table 1). Agricultural land is by far the largest contributor to the study area, as it constitutes 53.58% of the study area (Table 1). Forested areas and the varying soil types are also important aspects of this study area. Forested areas occupy 51.82 km² of land in the study area (34.1% of the study area) (Figure 9; Table 1), and for soils, classifications include muck, sand, and loam (Figure 10; Table 2). For this study, organic soils such as peat were grouped together as muck because of their similar properties, highly permeable soils with high proportions of sand were grouped together as sandy soils, and loam soils were grouped together because these soils often have relatively equal proportions of sand, silt, and clay. Sandy soils are the most dominant within the study area, as they occupy 86.92 km² (57.2% of the study area) (Table 2). Open water (i.e. lakes, rivers, and ponds) occupies 3.86 km² of the study area (2.5% of the study area), while wetlands occupy a small portion of the study area with 0.31 km² of land (0.2% of the study area) (Figure 9; Table 1).

---