Half a Century of Vertical Riverbed Deformations due to In-Stream Mining.

The rate of deformation of the longitudinal profile for a period of half a century in the sediment flow and riverbed morphology has been assessed by comparison of the leveling survey data on the longitudinal profile of a number of lowland rivers in Russia. This problem remains relevant in both the theoretical and practical aspects, especially for rivers in which a range of in-stream mines occupies kilometers and tens of kilometers and they have operated for decades. The removal of a large amount of alluvial material from the sediment transport and changes in the riverbed morphometric characteristics have given impetus to the leveling process of the sediment transport capacity along the river due to scouring. The result is lowering of the bottom and water surface. The scouring reaches 3–8 cm in rate and spreads 400–700 m/yr along the river. Retrogressive erosion (headcutting) is well-defined, whereas progressive erosion is less pronounced, because it is partially replaced by the mechanical removal of alluvial material. Under these deformations, the longitudinal profile has changed from convex or straight to concave, and there are no signs of recovery over the past decades, despite the fact that the mining has been relatively moderate for the past 30 years or has been completed in the rivers under consideration. [ABSTRACT FROM AUTHOR]