Increased water temperature, altered flow rates, increased sedimentation: waterways are severely affected by heavy rainfall. At the same time, even the smallest urban streams provide a habitat for many fish.

Sophie Duchesne, professor of hydrology and urban infrastructure at the Eau Terre Environnement Centre of the Institut national de la recherche scientifique (INRS), saw the Visage Municipal program as an opportunity to join forces with her colleagues Geneviève Pelletier from Université Laval and André St-Hilaire, also from INRS, whose research interests include fish habitat. Combining their expertise, they decided to study the impact of urban rainwater management on fish habitat.

Two streams, Ruisseau Juste-Plourde in Rivière-du-Loup and Ruisseau Tardif-Bizier in Adstock, were chosen as study sites. In a project spanning two observation seasons – from May to November – the research team collected measurements of rainfall, stream flow, water level, turbidity, and other parameters. These data enabled the team to develop a predictive model that will be used to measure the future impact of climate change, particularly during episodes of extreme heat or heavy rainfall.

Despite the relatively modest size of the study, it highlighted the high numbers of fish in certain small streams. Climate change and, consequently, an increase in the number of days with excessively high temperatures will have a direct impact on their optimal development. In Rivière-du-Loup, for example, the project led to the development of a methodology for measuring runoff and stream water temperatures that can be used in other rivers and municipalities.

These results will help Québec municipalities manage their rainwater in new ways to better protect fish.