An Assessment of Suspended Load Estimation Methods by Rating Curve in the Flood Condition: A Case Study of Glinak Basin, Alborz Province

Sediment suspended load is one of the largest contaminated non-point sources and major factor in the degradation of surface water quality. In general، there are many hydraulics and statistical methods to estimate suspended load. The hydraulic models of sediment transport cannot predict suspended loads correctly، but the rating curve models (statistical methods) are common hydrological methods to estimate suspended load that are frequently used. The goal of this research is determining the efficiency of common hydrological methods for estimating flood rivers suspended load and also selecting the best method for estimating the sediment that carried out in 1971 to 2011 in Glinak station of Taleqan basin. In this regard، four rating curve methods including one-linear، two-linear، mean loads within discharge classes and FAO were compared by RMSE، MAE، R2، Standard Deviation and Nash-Sutcliffe criteria''s. The results showed that the Mean load within discharge classes'' method by MAE 6583 ton/day، correlation efficiency (R2) 71%، RMSE 6751 ton/day and NS، 0. 57 is more accurate than other methods. Also changing the used data in hydrological methods changes the best method. Furthermore، increasing the flow discharge in river leads to increase of the error in the rating curve models.