Home – Home – Jornals – Geography and Natural Resources 2020 number 4

The synoptic situation that developed in the summer of 2019 in the southwestern areas of Irkutsk oblast region, in the mountains and foothills of Eastern Sayan, was responsible for heavy rainfall that caused extreme flooding on the Iya river. A landscape-hydrological analysis of the territory was made. It was found that topography, morphology and structure of soil and vegetation cover have a considerable influence on the hydrological regime of the river and on the formation of the flood runoff. An important role for the operation of the hydrological functions of landscapes in the formation of this flood is played by the intensity, duration and spatial differentiation of precipitation, coupled with the state of the underlying surface within the Iya basin. During the period of extremely high precipitation, the landscapes of most of the catchment were characterized by a sig nificant humidification moisture resulting from preceding precipitation, which reduced their regulation and accumulation capac ity. Goletz, subgoletz and mountain-taiga larch landscapes on frozen tundra soils of the northeastern macroslope of Eastern Sayan which are characterized by large slope angles, sparse vegetation and a shallow soil layer, are distinguished by large water yield in conditions of heavy precipitation. A significant flow-regulation potential of mountain-taiga dark coniferous land scapes of gentle slopes and low mountains, and also the accumulating properties of meadow-marsh complexes of foothill depres sions and valleys were realized during the previous precipitation events and did not have a significant regulatory effect during the formation of the flood at the end of June. Hilly-ouval topography and a high groundwater level in the middle part of the basin are the factors promoting flooding thus impeding infiltration and outflow of water.