Comparison of Different Methods for Estimating Bed Load using developed software of STE (case study: Babolroud River)

The estimation of sediment load is vital for designing the crossing structure and rehabilitation of rivers. Bed load transport in alluvial channels has been studied extensively and different equations are presented based on laboratory or field data. Estimating of bed load transport rates using different equations gives different results. Due to the complexity of the interaction between sediment transport and flow behavior, there is still a high level of discrepancy ratio between the estimated and the measured values. Therefore, in each river, according to its hydraulic and geometrical conditions, it is necessary to choose the best equation that has a higher accuracy to estimate bed load in that river. In order to achieve a better estimate of an equation, we must carefully compare the conditions of the study area with the conditions and assumptions in which each equation is formed, so that a more appropriate and logical answer can be found which is closer to reality. Therefore, it is very important to achieve new and innovative methods that can improve accuracy in calculating different estimation methods for sediment loads in rivers. According to different methods of estimating sediment load in the rivers and their high computing volume the need for a comprehensive computational software to increase accuracy, as well as to compare the different results obtained from these methods in this field, is vital.

Considering that there is still no software that can use most of the existing equations to calculate sediment load in the rivers and provide the best equation among them, in this research by developing a user-friendly software named “Sediment Transport Estimator (STE)”, which is designed in the VB.NET programming language in the Windows environment, the ability of available equations of estimating bed load in Babolrood River of Mazandaran province in 3 reaches with the names of Anarestan, Daronkola and Kelarikola, in which bed load is measured, has been evaluated.

The results showed that by using the developed software the best method for estimating bed load in the studied river is Toffaleti method with an abundance of discrepancy ratio between 0.5 to 2, 69.2%. In this case, the abundance of discrepancy ratio between 0.5 to 2 for the reach of Anarestan, Daronkola and Kelarikola is 66.7, 100 and 50 percent, respectively.

The equations Toffaleti, Yang, Yalin, Einstein-Brown and Ackers-White, respectively, offer better results than other equations, and the equation Toffaleti, in which 69.2% of the data are calculating in discrepancy ratio range of 0.5 to 2, is giving the best results in the studied river.