Monitoring of local coastal geosystems of the Bratsk reservoir

Abstract

According to the comparative analysis of digital elevation models (DEM) based on large scale topographic surveying at the Bykovo site, a 746 m² maximal extension of landslide movement area was revealed in 2006, which was caused by maximum rainfall and the reservoir water level highest in the observation period. The areas prone to erosional form development on the landslide slope increased on 100 m². It was established that the Rassvet site on 2000 m extent in alluvial and deluvial loams and sandy loams with interlayers of medium sands is exposed to abrasive wash-out. The width of the shore slope edge retreat ranged from 0 to 8 m during the last three years. According to GPS survey data, the maximum volume of washed-out soil material reached 13860.0 м 3 over the 2006–2007 period. The total volume of the gullies in the edge of abrasive bench amounted to 1360.1 м 3 (2007). The volume of soil, lost at the Zakoryukovo site in the loess-like sediments as a result of a small shore edge retreat and erosional processes constituted 2590 м 3 in the same period. The highest volume increase (on 4486.34 m³ from 2004 to 2008) was revealed at karst-erosional mechanism on the Khadahan site. Based on interpretation of images (1971—1980), the mid-term dynamics of linear growth of shore gullies on the abrasive Uley site ranged from 0 to 44 m, average growth rate accounted for 1-2 m, with maximum of 4 m per year. At the present stage the shore zone of the Bratsk reservoir is marked by lack of stabilization of abrasion processes. The response reaction of local geosystems (dynamics of the processes, their interaction, and environment change) is characterized by a certain cyclicity corresponding to water level fluctuations.