CONTINUOUS HYDROLOGIC MODELING OF MAJOR FLOOD HYDROGRAPHS USING SEMI-DISTRIBUTED MODEL

Hydrological modeling is a commonly used tool to estimate the basin's hydrological response due to precipitation. Continuous hydrologic modeling synthesizes hydrologic processes and phenomena i.e., synthetic responses of the basin to a number of rain events and their cumulative effects over a longer time period that includes both wet and dry conditions. Continuous hydrologic modeling with the Hydrologic Engineering Center's Hydrologic Modeling System (HEC- HMS) is discussed in this study and an application to the Simly watershed is presented. Specifically, four flood periods were selected for calibrating and validation the continuous hydrologic model on daily time scale. The simulations provided hydrologic details about quantity and variability of runoff in the watershed. The model shows statistical value of R 2 >0.75 and NSE >0.71 with a reasonably good value of PBIAS for the whole calibration and validation period. These obtained square functions indicate satisfactory performance of HEC-HMS model in simulation runoff hydrograph. Sensitivity analysis indicated that most sensitive parameter in the Simly watershed was the CN and impervious area. The model produced reasonable results, but illustrated the need for more refined application of specific parameters.