The short-term changes of gully erosion forms in the context of the water level fluctuations in the Bratsk reservoir (Russia)

The results of investigations ascertain the influence of the water level regime on the erosion dynamics that was estimated according gullies volume change within the space-time between two measurements. The development of gullies in the shore zone is to a large extent influenced by the abrasion of shore slopes, which is intense at high water level in the reservoir. The minimum rate of gully development (4.5-54.7m3 yr-1) was due to the action of shore abrasion and eolian processes within the period of 2004-2007. A large positive dynamics can be attributed to the increasing number of erosion cuts. The maximum material loss from gullies (in total 627.66 m3 ) and the average volumetric retreat rate for all gullies (16.5 m3 yr-1) were recorded at the permanent lowering of the reservoir water level during the 2007-2008 period. Water level fluctuations cause cyclic changes in the dynamics of processes and initiate the new mechanism of erosion that is not typical of regular conditions