Modeling Non-Directly Connected Impervious Areas in Dense Neighborhoods

摘要

A dense residential neighborhood of 16.9 ac (6.8 ha) in Portland, Oregon experiences basementrnflooding problems and flow capacity problems in its combined sewers. Low impactrndevelopment (LID) alternatives, such as disconnection of downspouts from roofs, are beingrnexplored by the City of Portland as one means of alleviating the problem. The EPA Storm WaterrnManagement Model (SWMM) model has been used to simulate runoff from the area underrncurrent conditions and under hypothetical LID for which runoff from roofs and driveways isrndirected over adjacent pervious areas. Both an aggregated model representation (elevenrnsubcatchments) and a disaggregated model representation (118 subcatchments, including 115rnsubcatchments representing each house parcel) have been studied. Predicted hydrographsrncompare well with City of Portland Bureau of Environmental Services (BES) monitored flowsrnfor the neighborhood for both model representations. The hypothetical LID simulation results inrnover a 50% reduction in hydrograph peaks and volumes.