Detention Pond Sizing for Multiple Return Periods

A desk‐top method is presented to size detention ponds and the outlet facilities for multiple return periods. The method is based on the usual reservoir routing technique, which couples the hydrologic storage equation with those describing flow through the outlet structures. The equations are rearranged in terms of several dimensionless parameters. A computer model is employed to solve the governing equations using a finite difference scheme. The results obtained for carefully chosen combinations of the dimensionless parameters are generalized based on the concept of similarity. They are presented in chart form. These charts can be used directly, i.e., without a lengthy trial‐and‐error routing procedure, to size a detention pond that satisfies a set of design criteria requiring the control of runoff for at least three return periods. The use of the design charts are illustrated through a sample application.