Evaluation of Performance of Empirical Models of Storm Events Sediment Yield of Drainage Basin and Introducing Calibration Coefficients

Variable and dynamic nature of sediment transport by rivers and spatial and temporal variation of drainage basin sediment yield in general, especially during flood events, can lead to unreal and inaccurate judgments and faulty planning about erosion and sediment yield behavior of the drainage basin. Generally empirical models used to estimate the amount of sediment yield during flood events; however, there is little information on the accuracy and precision of such models. In this research, in order to evaluate the performance of the empirical models used to estimate the flood event sediment yield, at first the concurrent sediment and water discharge of some of the flood events (five events) were recorded on an hourly in the Poledouab hydrometric station located in Gharachay river of Markazi Province in a way that rising and falling limb of hydrographs included. Considering observed data of flood events sediment yield, the accuracy and precision of empirical model's estimations was investigated. The results show that there are two different kinds of estimation in the selected models. Some of them that overestimate the sediment yield include MUSLE model and its modifications, and those underestimating floods event sediment yield include sediment routing model and linear and mean class rating curves with bias correction factor of MVUE. Finally by considering observed value as a basis, the power of empirical equations calibrated for more accurate and precise estimation.