Simulation feasibility of sedimentgraphs, using time-area model

The proper prediction of temporal and spatial variation of sediment yield from the watershed is a need for sediment control، river engineering and soil and water conservation studies. The present study was therefore planned to simulate the sedimentgraphs for Chehelgazi watershed in Gheshlagh dam upstream in Kurdistan Province، Iran، using Time-Area Model. Towards this attempt، the study area was divided to 7 time-area segments based on the time of concentration. The soil erosion in each segment was estimated using USLE model and then routed to the main outlet using sediment delivery ratio as a result of division the slope of downstream isochrones by adjacent upstream one. The temporal variation of sediment was ultimately predicted with the help of lag time of sediment arrival to the outlet and the concept of superposition for 11 storm events occurred during winter 2006 and spring 2007. The comparison between estimated sedimentgraphs with corresponding observed ones verified the weak performance of the model in simulation of sedimentgraphs under consideration. The results also verified the calibration necessity of the model to achieve appropriate estimation for important components of the sedimentgraphs. The results of the calibration finally proved the considerable capability of the model in predicting of total volume of sediment yield with respective estimation and verification errors of 29. 05 and 38. 40%.