Impact of large water level fluctuations on geomorphological processes and their interactions in the shore zone of a dam reservoir

Bratsk Reservoir is the second largest reservoir in the world in terms of volume (170 km3) and one of the largest in terms of area (about 5500 km2). It was created in 1967 and is characterized by a long-term exploitation regime, with water level fluctuations of 1.1 to 6.6 m per year and up to 10 m per decade. We summarize a series of detailed field investigations and monitoring conducted in 2001-2013, concerning various geomorphological processes in the shore zone of Bratsk Reservoir. The processes were initiated (bluff recession, accumulation processes, aeolian processes, linear erosion) or intensified (karst processes and landslides) as a result of creation of the reservoir. The course of geomorphological processes is conditioned by water level fluctuations in the reservoir. In periods of high water level, coastal slope erosion with bluff recession and activation of landslides are observed, whereas during low water level, aeolian processes are activated, while karst processes and linear erosion are intensified. Geomorphological processes occurring near the shore of Bratsk Reservoir often interact. Although the reservoir has been exploited for nearly 50 years, the rate of geomorphological processes taking place in its shore zone is not declining, and the area where these processes take place is increasing.