Zoning of Towns in the Irkutsk Region According to the of Floods Danger

Methods of flooding zones identification using as satellite space images as digital elevation model in the QGIS geographic information system are considered. It has been determined that the digital elevation model is most effective method. It allows to more accurately identify the flooding zone boundary according to the elevation marks of the highest water level at the hydrological station. For studying the floods risk the small towns in the Angara River basin in Irkutsk region were selected (Tulun, Nizhneudinsk and Biryusinsk), which located on the floodplain areas of the Iya, Uda and Biryusa Rivers. Biryusinsk is subject to less flooding and consequences due to the location of the town on elevated areas of the right-bank terraces of the Biryusa River valley. Zoning of “Tulun town”, “Nizhneudinsk town” and “Biryusinsk town” according to the flood risk degree was carried out. According to relief elevation marks the four zones have been defined for each territory, which characterized by different degrees of flooding hazard (high hazard, medium hazard, low hazard and no hazard zone). An analysis of the main causes, as well as the structure of the flood zone during the catastrophic rain flood of 2019 in the cities of Tulun and Nizhneudinsk was carried out. He showed that, along with hydroclimatic factors (intense and abundant rainfall, high previous moisture content of watersheds), a significant role in the formation of great damage from floods was played by high population, economic development and development features of flooding areas of the Iya and Uda river valleys. The floods damage in Biryusinsk is less, despite the frequent observation of water levels above the critical level due to the city location on elevated area of the right-bank terraces of the Biryusa river.