This report provides a planning methodology and a design tool to help determine the appropriate location and volume of detention basins required to control critical storm events. The technique involves using watershed characteristics including the SCS curve number, time of concentration, peak outflow rate, watershed area and the storage recurrence interval to help predict these detention volumes.
Historical rainfall records are used in a revised continuous simulation program (SYNOP, Hydroscience, Inc,) to determine the rainfall excess from which runoff hydrographs are produced. Various combinations of the watershed characteristics were input and computer analyses done to obtain the required data base. A statistical analysis is performed in each computer analysis to obtain the statistics on the required volume. Graphs were drawn from these statistical results as functions of the watershed characteristics and the release rate. Entering the graphs with the governing watershed characteristics, the designer can obtain.a good estimate of the detention basin volume required
