Morphodynamics of the Channel of the Northern Dvina River, Its Natural and Technogenic Transformations in the XX–Early XXI Century

The article presents the main directions and conditions of the transformation of the Northern Dvina river channel (from the confluence with the Vychegda River), occurring under the influence of almost a century of anthropogenic impacts, fluvial deformations and hydroclimatic changes; the contribution of each of these factors and their interrelations are determined. The study is based on analysis of field measurements (branching water discharges, flow velocity fields, turbidity and sediment composition) taken during the 2024 flood period, river maps showing channel conditions at various times since the 1960s, satellite imagery and riffle and riffle area maps. It has been shown that the reformation of the northern Dvina channel takes place in the wide floodplain and adapted channels, and in those sections of the incised channel where it is formed in moraine or Permo-Triassic sediments. The main factor of transformation is anthropogenic, namely dredging and straightening to ensure the required dimensions (mainly channel depth) of the waterway. Due to the amount of work carried out, their influence is much greater than the role of changes in water flow, which for the Northern Dvina is manifested in an increase in annual flow with a decrease in water availability during floods and an increase during low flow periods. Dredging and straightening has resulted in more complex branching in most sections of the channel in a wide floodplain and adapted channel. However, the construction of dams, including those that overtopped arms, has resulted in simplified channel branching in some sections of both incised and wide floodplain channels.