Although knowing the extent of fluvial suspended sediment load in water projects and the field of water resource engineering has crucial importance, subtle and comprehensive studies have not been conducted in this field. Hydrologic methods are commonly used to estimate the fluvial suspended load. The purpose of this study was to obtain the most appropriate equation to estimate suspended load and determine the specific rate of sedimentation in the watersheds in Mazandaran province. In this study, by use of six methods namely, model of a linear rating curve, categories of data as monthly, seasonal and annually, mean of groups and classification of data based on high water and low water flow months, different types of sediment rating equations are provided and the best model to estimate the suspended load is selected. To conduct this study, the corresponding data of water discharge and suspended sediment discharge that are measured randomly on some days of a year at hydrometric stations, were used. To estimate the long-term average of annual suspended load, the data of daily and monthly average of flow are used. Finally, the best model for each station was chosen by use of statistical parameters such as Mean of Square Error (MSE), Determination Coefficient (R2), Relative Mean Error (RME) and Modeling Efficiency of Nash Sutcliffe (EF). According to the evaluation of 26 hydrometric stations studied in this research, annual, monthly and mean of group models had the best estimate of the suspended load, respectively. The investigation of sediment traort in different seasons revealed that sediment traort of watershed in Mazandaran mostly occurs in spring. The results of the calculation of the specific rate of sedimentation in the under study basin, shows the specific rate of sedimentation in this basin is between the low and average rang. The sediment rating curves at the studied stations, perform the estimation of the suspended load with (-65) - (20) percent error relative to the actual amount and as average, this amount for all stations was estimated equal to -18 percent.
