Interlinking erosion susceptibility, channel geometry and stream power: a case study of the Mayurakshi River, eastern India

One of the major geomorphic processes that have assumed significance and turned into a quasi-natural hazard in the Anthropocene is soil erosion. Apart from the loss of millions of hectares of cultivable land, this sub-aerial process is associated with increased sediment load of rivers, thereby causing rapid siltation. Since the process of actual measurement of erosion is quite complex, geomorphologists have been dependent on prediction-based empirical models for ascertaining the erosion susceptibility. However, in humid areas of the globe, running water contributes most to the process of erosion. This is very much dependent on the channelized flow, which, in turn depends on the channel cross-section and fluvial hydraulic parameters. It has been found that in spite of greater probability of the erosion conditioning factors, the removal of top soil by the rivers is often subdued because of unfavourable hydraulic factors. So, the process of interlinking the predicted soil loss with the fluvial hydraulic parameters becomes significant in this realm. This study has, therefore, tried to correlate the RUSLE-based empirical erosion model with the fluvial hydraulic parameters of bankfull discharge, shear stress and unit stream power. Analysis reveals that a moderate positive correlation exists between them (r = 0.48–0.502). The moderately positive correlation between these factors suggests the fact that in areas where the erosion is higher, there is more possibility of elevated values of the hydraulic attributes. In other words, it implies that the fluvial hydraulic parameters help in augmenting the impact of erosion and removal of the top soil in this area to some extent. This is especially true in the middle domain of this basin in the vicinity of the Massanjore Dam on the Mayurakshi River. This is expected to contribute in enhancing the speed of sedimentation of the dam besides reducing the soil fertility and crop productivity in the entire area. In the lower domain also, it was observed that above tolerance soil loss is prevalent in most of the areas. Efficient conservation techniques such as agro-forestry in the upper and middle domains as well as straw mulching in the lower domain are the need of the hour to prevent further deterioration.