In urban stormwater management, ''soft'' solutions are being widely applied, including stormwater source control. However, no specific resource-effective model is available to assess their effects at the city-scale. As a consequence, source control regulations are often based on simplistic hydrologic assumptions. In this paper, we apply a top-down modeling approach to this problem, and we develop a simple model of flow-rate attenuation in the sewer system, using a numerical empirical approach. Then, we apply the model to source control regulations, assessing which type of regulation is more effective depending on relative positions in a catchment. We show that a model requiring only two types of information about a catchment (concentration time and pluviometry) can provide relevant information on source control effectiveness. This information could be helpful, for example, to define a stormwater zoning.