NATURAL AND ANTHROPOGENIC IRREVERSIBLE VERTICAL RIVERBED DEFORMATIONS

Abstract

Irreversible vertical deformation implies the systematic incision or sediment deposition within a considerable length of the river, in the course of which rise or lowering of river long profile and change of its general shape occur. Contemporary deformations occur in time intervals documented by historical materials and direct observations, that span several centuries, develop under the human influence or have a purely anthropogenic origin, although natural deformations due to tectonics and climate change play some role as well. To analyze the dynamics of the riverbed vertical deformations process, published sources for several rivers over the World were used as well as authors’ own studies in a number of rivers: Ob river upstream and downstream of Novosibirsk reservoir, Kama river downstream of the Votkinsk dam, Selected reaches in rivers Tom’, Oka, Belaya Rivers with a large scale in-stream mines. Dam construction and creation of reservoirs as well as in-stream extraction of building materials most notably contribute to the development of vertical deformations. Results show that both the process of incision downstream of dam and in sections with in-stream mines and the process of regressive accumulation upstream of the reservoirs are described by an exponential relationship reflecting the asymptotic nature of the lowering or rise of the riverbed. The relationship coefficients depend on the mobility of the channel. In the course of incision, riverbed becomes less movable, and its recovery may occur in other hydrological and geomorphological setting.