Small-Storm Hydology and BMP Modeling with SWMM 5

It is now largely recognized that stormwater management practices should include not only quantitative aspects for flooding control, but also measures that can minimize the impacts on stormwater quality and the erosion in watercourses. The BMPs (Best Management Practices) that are specifically designed to reduce these impacts generally consider small to moderate rainfall events and the hydrologic modeling of these events is in some respect different from the modeling of the larger storms that are typically used in purely quantitative control.

Small-storm hydrology features have been defined and studied for the past 20 years (Pitt, 1987; 1994) to examine the specific elements that should be taken into account for the design of BMPs used for recharge, quality and erosion control. After a review of small-storm hydrology concepts and the main findings as they are currently applied, the paper describes how SWMM5 (implemented in PCSWMM.NET) could be used to model the hydrology processes for different types of BMPs and reproduce results obtained empirically in small-storm hydrology research. Filter strip, infiltration trench, porous pavement and bioretention are discussed and analyzed with SWMM5, with specific sensitivity analyses for design storms, soil parameters and design criteria.