Applicability of Instantaneous Unit Sediment Graph Model in an Iranian Large Watershed

Abstract

Development of the sediment graph which is the temporal distribution of sediment load during flood incidents is essentially required for accurate estimation of sediment yield of the watershed. Unfortunately, sufficient information and data with which to estimate the sediment graph are rarely available and often can only be obtained through a costly field survey or equipping. Development of the sediment graph models based on the easily accessible physical characteristics of a watershed and precipitation data is therefore a viable and convenient tool for the efficient control of soil erosion and sediment yield. The instantaneous unit sediment graph (IUSG) described herein produced as the product of the instantaneous unit hydrograph (IUH) and the sediment concentration distribution is supposed as one of the convenient procedure leading to develop sediment graphs. In the present study, an attempt has been made to develop a conceptual model of an IUSG for suspended sediment prediction in the Khanmirza watershed in Iran comprising an area of 395 km2. The procedure involved the translation of the rainfall and the attenuation by routing of the sediment through a cascade of identical linear reservoirs to the watershed outlet applying the Clark and Muskingum approaches. Simulated sediment graphs generated by convolution of IUSG compared acceptably with the respective observed data. The results also showed that the model has the considerable potential in watersheds where no comprehensive data exists.