Against the background of recent climatic fluctuations, the number of catastrophic hydro meteorological processes is increasing. In this work, the problem of updating the methods for assessing the risks of hazardous hydro meteorological phenomena (OHP) for the rivers of the drainage basin of Lake Baikal by the method of selection of theoretical distribution laws based on the available empirical data of the maximum annual water levels. The maximum water levels are calculated for catastrophic levels of 0.1% and 1%. For the assessment, a risk scale was used, where the increments in the height of the maximum water levels are categorized according to the degree of risk of occurrence. It was revealed that a very high risk of floods is typical for the basin of the Barguzin and Selenga rivers; the rivers Goloustnaya, Vydrina and Verkhnyaya Angara are characterized by an average risk. Geoinformation methods were applied to solve the problems of forecasting the possible areas of flooded zones using the example of the river. Upper Angara - with. Upper Zaimka.