A Rainfall-Runoff Simulation Model for Estimation of Flood Peaks for Small Drainage Basins GEOLOGICAL SURVEY PROFESSIONAL PAPER 506-B A Rainfall-Runoff Simulation Model for Estimation of Flood Peaks for Small Drainage Basins

A parametric rainfall~runoff simulation model is used with dat~ from a point rainfall gage and data on daily potential evapotranspiration to predict flood volume and peak rates of runoff for small drainage areas. The model is based on bulkparameter approximations to the physical laws governing infiltration, soil-moisture accretion and depletion, and surface streamflow. Three case studies are presented in which an objective fitting method is used for determining optimal best-fit sets of parameter values for the data available for use in predicting flood peaks. Errors of prediction result both from errors in rainfall input and from lack of model equivalence to the physical prototype. These two sources of error seem to be of the same order of magnitude for a model of the level of simplicity of that present~d. Major gains in accuracy of simulation will require improvements in both data and model. The limit of accuracy of prediction of flood peaks by simulation with a bulk-parameter model using data obtained from a single rain gage seems to be on the order of 25 percent.