Do stormwater source control policies deliver the right hydrologic outcomes?

The number of stormwater source control (SC) regulations adopted by local authorities is rapidly growing in many countries. We can expect that, in the near future, the hydrologic behavior of many urban and periurban catchments will reflect this diffusion. This paper discusses SC regulations through two complementary approaches: starting on three French case-studies, it analyzes how regulations are developed today and identifies a set of shortcuts in policy-making practices. Then, the hydrologic model of a periurban catchment in the Paris region is used to test the impacts that these regulations can produce if widely applied. The main finding is that inertia in policy-making, driving a singular focus on flow-rate based regulations, can produce negative impacts in the long-term. Further efforts on volume-based regulations are advocated, both in terms of research and policy-making.