Preparing hydrologic DEM and its application to produce a accumulated flow map (A Case study at Upstream of Karkheh dam)

Digital elevation model (DEM) reconditioning methods are being used to improve its quality to be used in simulation and cellular hydrological modeling. In this paper , methods of improving DEM and creating “Hydrologic DEM” with using the ArcHydro1302 extention were studied and also evaluated in 40 subbasins of Karkheh river basin(KRB) and one of its applications in “accumulation runoff map” was implemented .Streamflow information is available at hydrometric stations as points but for determining the amount of river discharge continually at any point along the river and branches, it is needed to accumulate the runoff map. The 9 direction method (D9) is the basic model for river network delineation from DEM accumulated cells. In this algorithm, the flow of each cell pours to one of the eight adjacent cells in the "hydrologic DEM ". In hydrologic DEM the accumulated cells in the river line forward to the downstream increase continuously. With "Agree algorithm" and with trial and error the DEM improved and the upstream area of accumulation cells, have been compared with a vector area in each subbasin which correlation coefficient was 308894. After preparing runoff map of the basin, accumulation flow(accumulated runoff map) using a weighted cumulative flow function was created with 233m cell size then the continuous flow map was presented. The results indicate that the error between estimated discharge from accumulated flow map with observed discharge in 40 subbasins varies between 3029 to 001 percent.