Unit‐hydrograph lag and peak flow related to basin characteristics

Abstract

Unit‐hydrograph lag and peak‐flow values have been empirically related to basin characteristics and to the duration of rainfall excess. Characteristic data for 20 basins ranging from 20 to 1600 sq mi of drainage area and located in the North and Middle Atlantic States were used in the study. Unit‐hydrograph values were obtained from 65 rainfall excess periods.The study indicates that the most significant basin characteristics were drainage area, length of longest watercourse, length to center of area, and equivalent mainstream slope. Graphs of the correlation studies are given and a method for determining equivalent main‐stream slope is presented. A nomograph for the computation of synthetic unit hydrographs is included and is based on equations developed in the study. The data presented will aid in the determination of unit hydrographs for ungaged watersheds in similar areas.