My Sponge Property: Private-Sector Adaptation Measures to Enhance the Resilience of the Built Environment to Stormwater Flooding

Canada is experiencing an increase in the intensity and frequency of extreme rainfall events as a direct consequence of climate change. Since 2022, the Greater Montreal region has been affected by extreme rainfall events every year, exceeding the capacity of drainage systems and causing major flooding, notably in urban topographic depressions where runoff accumulates. On August 9, 2024, Hurricane Debby generated more than 70,000 home insurance claims in Quebec, making it the costliest natural disaster in the province’s history. These impacts are largely attributed to the absence of adequately designed major drainage systems in most of the built environment, resulting in significant economic and social consequences.

This project aims to evaluate the potential of low-impact development (LID) strategies implemented on private properties to reduce flooding in vulnerable urban areas. A case study is conducted in a major city in Quebec where recurrent overland flooding has been observed over recent years. Various LID measures, including rain gardens, blue roofs, rain barrels, and infiltration trenches, are implemented on residential properties, where site conditions allow. Hydrologic and hydraulic simulations are performed using a coupled 1D–2D approach with a calibrated PCSWMM model, enabling quantitative comparisons and spatial visualization of flooding depths and extents under multiple scenarios.

Results indicate that substantial runoff volumes can be retained on private properties, often at a lower unit cost than conventional public-domain interventions, such as retention ponds and underground detention basins. These findings highlight the potential of distributed, source-control strategies to complement traditional drainage infrastructure. The next phase of the project will focus on identifying key barriers and opportunities related to implementation, coordination and stakeholder engagement, particularly involving municipalities, property owners, and insurers, to support broader adoption of private-domain LID strategies and enhance urban resilience to extreme rainfall events

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