Variability of Sediment Rating Equations in the Length of some Rivers of Kermanshah, Kurdistan, Zanjan and Gilan Provinces

The study of sediment transport capacity and sediment transport process has especially important in rivers hydraulic and its morphology. Given that, the changes studies of corrective coefficient in various methods of sediment estimation can be useful, therefore, the present study for the changes comparison of corrective coefficients from up-stream to down-stream Gharasu river (Kermanshah), Negel and Sarvabad rivers (Kurdistan) and Ghezelozan river (Kurdistan, Zanjan and Gilan) was conducted using LQMLE, Smearing, CF1, CF2, normal and FAO hydrology methods. The results showed that from up-stream to down-stream river, the erodibility in up-stream watershed of stations decreased with rerducing equation coefficient and the sediment transport increased with the enhancement equation power. The reducing and decresing equation power and coefficient in down-stream direct of various cross sections of rivers can be added the areas with less slope to up-stream watershed. In studied stations, the applied hydrologic methods (expect FAO method) estimated the sediment rate less than observed sediment rate. Also, the comparison of observed and estimated sediment rates showed that the down-watershed stations had the estimated sediment difference less than toward up-watershed stations.