An Evaluation of Low Impact Development and Residential Basement Flood Risk in the Greater Toronto Area

Low impact development (LID) is a modern engineering design strategy that functions to mitigate the negative impacts of increased stormwater runoff and pollution by managing stormwater quality and quantity. It was hypothesized that the incorporation of LID may exacerbate hydrologic conditions and contribute to residential basement flood risk. The hydrologic model PCSWMM was used to assess the influence of LID on net infiltration depth and groundwater elevations using continuous simulation for a one-year period for three case-study sites located in the Greater Toronto Area. The inclusion of LID did influence site hydrologic parameters, though these results are inconclusive. However, it can be inferred that the increased risk of basement flooding due to exacerbation of hydrologic parameters would depend on the extensiveness of LID implementation. A novel methodology for the assessment of LID influence on residential basement flood risk was established using hydrologic modeling and probabilistic assessment techniques.