Emphasis is not only on peak flow reduction but also storm Water Quality Control (WQC). Urban stormwater management practices, therefore, include the designing of retention ponds, infiltration systems, wetlands, etc. Sizing these WQC basins are very important. Contrary to popular belief that the bigger the pond the higher the WQC, evidence shows that after a certain threshold, sediment removal becomes negligible. A WQC basin is designed to capture a target percentage of a rainfall time series described by the capture curve. Capture curves are the graphical representation of basin volume and its corresponding runoff capture percentage generated from long term observations of rainfall events.
The incorporation of Capture Curves is a unique feature of VO-SWMM. It provides the option to analyze the impacts of large storm rainfall events on catchbasin capture rates (improved dual-drainage concept), surface, and basement flooding. This program contains a library from which established slopes can be interpolated to create new Capture Curves for analysis.
