Assessment of the fraction of bed load concentration towards the sediment transport of a monsoon-dominated river basin of Eastern India

Given the challenges of re-creating complex bed load (BL) transport processes in rivers, models are preferred over gathering and examining field data. The highlight of the present research is to develop an approach to determine the ungauged bed load concentration (BLCu) utilizing the measured suspended sediment concentration (SSC) and hydraulic variables of the last four decades for the Mahanadi River Basin. This technique employs shear stress and SSC equations for turbulent open channel flow. Besides, the predicted BLCu is correlated with SSC using a power relation to estimate BLCu on the river and tributaries. Eventually, different BL functions (BLF) efficiency is assessed across stations. The model predicted BLCu is comparable with the published data for sandy rivers and falls within +/- 20%. Outliers in hydraulic and sedimentological statistics significantly influence estimating the BL fraction apart from higher relative ratios and catchment geology. The constants of power functions are physically linked to sediment transport configuration, mechanism, and inflow to the stream. The stream power-based BLF best predicts the BL transport, followed by shear stress and unit discharge approaches. The disparity in the estimation of BLCu results from station-specific physical factors, sampling data dispersion, and associated uncertainties.

Automated summary

Given the challenges of modeling complex bed load transport processes in rivers, this research focuses on developing a method to determine ungauged bed load concentration using measured suspended sediment concentration and hydraulic variables. The approach uses shear stress and suspended sediment concentration equations for turbulent flow and correlates the predicted bed load concentration with suspended sediment concentration. The study evaluates the efficiency of different bed load functions across stations and finds that the stream power-based function best predicts bed load transport. Disparities in estimation arise from station-specific factors and uncertainties.