Big river channel formation and deformation in the intermountain basin (case study of the Yana River within the Kular mountain massif)

The incised pebble-boulder channels of large mountain rivers (including the Yana in its mountainous area), their morphology and history of formation are well studied. However, local conditions within the intermountain depressions lead to the emergence of specific features of the channel development and its morphology — in this case, the formation of finger-shaped meander. The paper analyzes the historical and modern features of the formation of the Yana riverbed in the “Porogi” section located in the depression inside Kular range, and describes the negative impact of channel processes on navigation. Using this case study, we consider the characteristic features of the channel development of a large river under the influence of a complex of factors — the regional geological conditions (which caused active incision of the channel), discharge, and channel sediment composition. Characteristics of lateral migration and curvature development of meander controlled by bedrock and narrowing of the valley are presented. The discharge conditions under which the displacement of riffles is possible are calculated. The forecast of the further channel development and recommendations for sustainable navigation are given.