Probabilistic Models for Urban Stormwater Management

Urban stormwater management is implemented through the adoption of non-structural practices and the use of structural infiltration, conveyance, and storage facilities designed to control the quantity and improve the quality of runoff from urban areas. This chapter introduces two statistical approaches recently developed and applied to urban stormwater systems. It presents Analytical Probabilistic Stormwater Models (APSWM), which allow for the estimation of the frequency of several variables of relevance for hydrologic analysis and design using closed-form analytical equations. This chapter introduces uncertainty analysis applied to urban catchments, particularly to the performance of Best Management Practices (BMPs), which are widely used to control the quantity and quality of urban runoff. Several methods, differing in their assumptions and level of complexity, are described and used to demonstrate that designs based only on median conditions cannot provide reliable pollutant removal rates.