Vertical riverbed deformations due to in-stream mining

Abstract

Comparison of the longitudinal profile of a number of lowland rivers in Russia, revealed their deformation due to a half-century of sediment flux and channel morphology adjustment. This problem remains relevant both in theoretical and practical aspects, especially for rivers where long-term mining of sediments from the stream beds extends from kilometers to tens of kilometers. The removal of a large amount of alluvial material from the sediments transport and changes of the riverbed morphometric characteristics triggered the process of leveling the sediment transport capacity along the river by the scour and resulted in a lowering of the bottom and water surface. The intensity of the incision reached 3–8 centimeters, and its progradation along the river 400–700 meters per year. Retrogressive erosion is pronounced, while progressive one is less pronounced, because partially replaced by mechanical removal of alluvial material. Over the past decades the shape of the longitudinal profiles changed from convex or straight to concave with no signs of recovery, despite the mining has been quite moderate for last 30 years or completed on the explored rivers.