Analysis of horizontal channel deformations based on stationary observations

The dynamics of bank erosion was estimated based on the stationary observations within the Khanty-Mansiysk Autonomous Region – Yugra, in the latitudinal section of the Ob River. The results include data on the deformations of river channels and floodplains, necessary for assessing and forecasting the negative impact of bank erosion on economic activity and taking timely measures to prevent it. Monitoring was carried out at the Ust-Vakhsky station using various methods including morphometric field mapping, cartography, photogrammetry and remote sensing. According to the study, the average long-term rate of bank retreat over the observation period is 3.9 m/year. The maximum rate of 17.5 m/year of the bank edge retreat was recorded in 2004. The results helped to estimate the amount of land erosed during four periods of erosional activity: from 1982 to 1994 – 416.2 thousand m² (annual erosion rate was 34.7 thousand m²/year); from 1994 to 2001 – 225 thousand m² (32.1 thousand m²/year); from 2001 to 2014 – 200.8 thousand m² (15.4 thousand m²/year); from 2014 to 2021 – 134 thousand m2 (19.1 thousand m2/year). The total eroded area accounts for 976 thousand m² for the observed period from 1982 to 2021 (with an average erosion rate of 26.3 thousand m²/year). The total volume of sediments that entered the river as a result of bank erosion was about 4.9 million m³. The most active period of erosion on the right bank of the Ob River was from 1982 to 1994 with an average erosion rate of 6.9 m/year, which is associated with high water levels. Result of the study were compilated into a database and were used in a probabilistic model of short-term and long-term forecasts of horizontal channel deformations of the latitudinal section of the Ob River, where free bends are formed, and the floodplain is dissected by numerous channels. According to two trend lines, the predicted rate of bank eroson for 2022 range from 2.0 to 2.8 m/year and for 2030 from 1.1 to 5.4 m/year.

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