ASSESSMENT OF VERTICAL DEFORMATIONS OF RIVER CHANNELS BASED ON HYDROMETRIC DATA
V.V. KRAVCHENKO
V.B. Sochava Institute of Geography, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia
Keywords: river channels, vertical deformations, hydrometric data, calculation methods, relationships between water flow rates and levels, lowest elevations of channels
Abstract
Methods for calculating vertical channel deformations based on hydrometric observations at the network of Roshydromet posts are considered. A method based on the relationship between water flow rates and levels is evaluated. It is concluded that the use of this method causes a number of serious difficulties and contradictions which do not allow its use in mass calculations. A method for assessing deformations based on using the lowest elevations of the channel is proposed. These marks are calculated from measurements of the channel simultaneously with the regular determination of water flow rates. The method was tested at 41 stations with a catchment area from 116 to 186 000 km2 in the basins of the Angara, Upper Lena, Vitim, and Lake Baikal. The data were used for the entire observation period, with a duration of 35 to 80 years from 1943 to 2017. Vertical deformations are noted at all posts without exception. Their characteristic amplitude for the observation period is 50-150 cm. At one quarter of the posts, this value reaches 150-300 cm. The trend of deformations is multidirectional. In 41 and 39 % of cases, scouring and alluvium were observed, respectively. At the other posts, the trend is not pronounced. The calculations and the examples of their interpretation show the ability of the approach described to reveal various features of the process of vertical deformation of river beds. In particular, on its basis, it is concluded that there is a relationship between deformations and water flow rates when the same water flow rate on small rivers can produce tens of times more work of deformation of the channel bed than on large rivers.
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