Document Type : Research Paper
Authors
1 Scientific Board, Soil Conservation and Watershed Management Research Institute, Iran
2 Scientific Board, Soil Conservation and Watershed Management Research Institute, Iran
Abstract
In calculation of catchments time of concentration, TC, lump equations are often used. Therefore, TC is not accessible for different parts of the catchments. In this research, using object oriented programming in the GIS environment a fully distributed model has been designed and developed. The model is able to calculate the time of concentration for any parts of the catchment to its outlet in a raster map. Model input layers are DEM, rainfall intensity, Manning’s roughness coefficient and catchment stream network. The most important outputs of the model are slope, flow direction and flow accumulation layers and isochronal surfaces. In the presented model, catchment cells are divided into two basic classes including channel cells and overland flow cells. Kirpitch and Kinematic wave equations have been used to calculate the time of concentration for the channel and overland flow cells respectively. In addition, rainfall-runoff hydrologic software, RAFTS-XP, has been used to evaluate the accuracy of TC model results. The result of TC model shows that calculated travel time had suitable synchronization to real time, which has been estimated using observed events and the calibration of RAFTS-XP. Considering the point that catchment response for all events which used by RAFTS-XP is based on different rainfall intensities with identical time of concentration, so observing different behaviors in flood hydrographs seems reasonable.
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