Design Hydrographs for Small Watersheds in Indiana

The results of a hydrograph study for small watersheds in Indiana are presented. The main purpose is to determine the shape of the hydrograph and the peak discharge for those areas where no stream gaging station is available. A mathematical expression of the hydrograph containing certain parameters that can be correlated with identifiable and readily obtainable watershed characteristics provides the theoretical basis for establishing the synthetic hydrograph. Seventeen small watersheds in Indiana were analyzed to determine the relationship between two hydrograph parameters (time to peak and storage coefficient) and three watershed characteristics (drainage area, length of main stream, and mean slope of main stream). A complete procedure for the design of the storm hydrograph for small, ungaged, watersheds is presented. The basic mathematical expression for the hydrograph is considered appropriate for general application.