Modeling of flood events using spatially distributed unit hydrograph

Abstract

In this study surface runoff resulting from isolated rainfall events has been estimated using spatially distributed unit hydrograph. The digital elevation model (DEM) was prepared from the contour map of watershed and used to extract the cell to cell flow path, flow direction, flow length, and slope. Soil Conservation Service-Curve Number (SCS-CN) method was used to compute the excess rainfall generated from each cells. The surface runoff generated from each cell was routed to the watershed outlet through the stream network. Kinematic wave equation was used to calculate the overland flow travel time of each cell in the watershed. The watershed Time Area isochrone was developed by summing up the time of concentration in each cell. S-hydrograph technique has been used to derive spatially distributed unit hydrographs. The distributed unit hydrograph has been convoluted with one hour rainfall excess hyetograph to get the direct runoff hydrograph for the storm event. The developed model was applied to five storm events and observed that the derived flood hydrograph of this model was closely matching with the flow records of the watershed. Indicating suitability of present modeling approach for predicting the direct runoff for given storm event of rainfall.