An Evaluation of Stormwater Management Practices to Provide Flood Protection for Watershed-Based Targets

The Credit River Watershed, within the province of Ontario, measures some 1000 km(2), and includes eleven member municipalities. The Watershed has been the subject of many studies and analyses focused on flood management since the early 1980s. Many of these initiatives have served to provide Credit Valley Conservation (CVC) with direction regarding the protection of historically flood prone areas along the main branch of the Credit River (know as Flood Damage Centres), for present and future land use conditions. The most recent initiative undertaken by CVC, termed the Credit River Flow Management Study (FMS), has adopted a watershed-wide assessment approach to flood protection for the main branch Flood Damage Centres. The study process for the FMS has involved using and updating the most current hydrologic and hydraulic models, which have been developed for the Credit River Watershed, in order to evaluate the effectiveness of various stormwater management strategies to provide the requisite flood protection for the Damage Centres, for the anticipated future land use conditions within the Watershed. This has included an evaluation of more traditional and conventional stormwater management practices, a sensitivity analysis of the rainfall distribution, as well as the development of a methodology for the assessment of lot-level Best Management Practices (BMPs) and Low Impact Development (LID) systems on a Watershed basis. The FMS has determined that, due to the intrinsic effects of runoff timing, distributed precipitation patterns and runoff volume increases, conventional practices are not suitable for flood control.