Application of the self-calibrating watershed model, opset, to a Gulf Coast watershed

The self-calibrating watershed model, OPSET, was applied to Cypress Creek, a 285 square mile. Gulf Coast watershed in Harris County, Texas. The model, originally developed at the University of Kentucky as a refinement of the Stanford Watershed Model, computes annual hydrographs, compares the values with stream gage records, and adjusts the watershed parameters until the best objective match is obtained. Modifications were made of the input options and optimizing procedures. The six years of data used (from the period 1951 to 1975) show good correlations of annual and monthly flows and consistent values of land phase parameters. Large floodplain storages and localized rainstorms prevented good optimization of channel parameters. It is suggested that the unit hydrograph method of channel routing be replaced by the kinematic wave technique. Results were extrapolated to future land use conditions, showing increases in peak flows with urbanization.