Geographical analysis of river floods and their causes in southern East Siberia

On the basis of analysing the genesis, recurrence and severity of flood hazards, a regional flood hazard analysis of the southern area of East Siberia has been carried out. The greatest flood hazard corresponds to the relatively densely populated area of southern East Siberia: the Upper Yenisei, Angara and Upper Lena river basins and the Lake Baikal watershed. Typically, the most hazardous floods include those caused by surges produced by damage to the dams of the Angara-Yenisei hydropower cascade; flash floods are also an extreme hazard. Maximum runoff factors were used to delineate regions within the study area, and the hazard severity was scored for the Irkutsk region. An inventory of the ice-dam and ice-jam areas, as well as of the streamflow sites with maximum runoff of different origins predominating in the Angara and Lena river basins, showed that the study area includes 78 and 19 ice-dam and ice-jam locations, respectively. A high recurrence of ice dams and ice jams is also observed on other rivers.