Results of Long-Term Observations Erosion of River Banks in Udmurtia

Aim. Quantitative analysis of long-term dynamics of bank erosion on small and medium-sized rivers of Udmurtia, which are important for modeling and forecasting the development of meanders necessary to prevent dangerous geoecological situations. Methodology. For the first time, the results of a study of channel displacement for 2003–2024 in 8 key areas located on small and medium-sized rivers of Udmurtia are presented. Geodetic survey was carried out on actively eroded areas of river bends using a laser tacheometer, which allows calculating not only linear erosion parameters, but also area and volume indicators. Since 2019, a satellite receiver has been used in instrumental surveys together with unmanned aerial vehicles. Results. It was found that for medium-sized rivers, the maximum erosion rates reach 6.15 m/year. The length of the eroded areas varied within the range of 115–533 m. The height of the studied coastal cliffs varies from 3.5 to 5.6 m. For small rivers, the greatest erosion values vary within the range of 2.3 to 8.14 m. The length of the eroded areas varies from 48–330 m. The average height of the eroded cliff on these rivers varies from 2.5 to 8.8 m. In the long-term dynamics of erosion on the Cheptsa (2 areas), Siva and Kyrykmas rivers, a positive trend is clearly visible with erosion maxima in 2011–2014, 2015–2016, 2019 and 2021. A close correlation has been established between the maximum width, area, and volume of erosion on the rivers Cheptsa (left tributary of the Vyatka), Siva (right tributary of the Kama), Kyrykmas (left tributary of the Izh) and their maximum annual discharges. The leading role of the bend curvature, the composition of the eroded rocks, and the order of the water flow, which we obtained earlier from benchmarker observations, is also confirmed. The location of intensively eroded areas within different types of bends is characterized by local features, but is more often confined to areas with the greatest steepness or shifted slightly downstream. Research implications. The results of the study are very relevant, since they can be used both for similar rivers of Udmurtia and for rivers of flat territories of the European part of the Russian Federation. The need for long-term field studies of erosion of river bank benches using modern instrumental methods is determined by the importance of identifying patterns of channel processes for making reliable forecasts of their development in specific landscape-geomorphological conditions in order to prevent dangerous geoecological situations.