Storm Hydrographs from Small Urban Catchments

The Rational method was reviewed, and found to be a special case of the kinematic wave solution under a uniform rainfall excess. In this study, a moving average procedure is introduced to the kinematic wave model. The kinematic wave solution is modified from an instantaneous rainfall to an average rainfall over a period of time of concentration. The revised kinematic wave solution provides the complete storm hydrograph with a peak flow consistent with the Rational method. This new method has been tested using 25 observed rainfall-runoff events from four urban catchments, and yielded a new formula for estimating the time of concentration. The moving average procedure was also examined by continuous non-uniform rainfall events. In general, the kinematic wave solution with the moving average procedure provides close agreements with more sophisticated watershed models for drainage areas up to 150 acres.