Abstract

In June and July 2019, on the left tributaries of the Angara river there occurred catastrophic rainfall floods inflicting enormous damage and human victims. The greatest damage was experienced by the city of Tulun on the Iya river. A comprehensive characteristic is given to the 2019 floods in comparison with similar events of the historical past and from the period of instrumental observations. An analysis is made of the characteristics of the flood hazard at gauging stations: their frequency and impact. The homogeneity of the series of the peak flood runoff is estimated against the background of climate change. The objects for study were the basins of the left tributaries of Angara river: the Irkut, Kitoi, Belaya, Oka, Uda and Biryusa, with a more detailed characteristic for the Iya river basin. The floods of 2019 were formed by extreme precipitation on the previously moistened surface of the catchments. In 2019, an exceptional hydrological situation developed in terms of both flood hazard characteristics and the devastating consequences for the city of Tulun. Nevertheless, catastrophic floods of a similar magnitude also reoccurred in the historical past and during the period of instrumental observations. The situation with two extreme floods during the summer season is also not unique. The event under study cannot yet be associated with climate change. Changes in the peak rainfall runoff series are mostly insignificant, even when the approximate runoff maxima of 2019 are taken into account. The decreased flood frequency over a later period may be associated with a low-water period that ended in 2019. Therefore, similar events can be expected to recur on the rivers of Irkutsk oblast, both within the Angara basin and within the Lena and South Baikal basins.

中文翻译：

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安加拉左支流盆地内的洪灾危险

摘要

2019年6月和2019年7月，在安加拉河的左支流发生了灾难性的降雨洪灾，造成了巨大的破坏和人员伤亡。破坏最大的是伊亚河上的图伦市。与历史过去和工具观测时期的类似事件相比，2019年洪水具有全面的特征。对测量站的洪水灾害特征进行了分析：其发生频率和影响。在气候变化的背景下，估计了洪峰径流序列的均一性。研究的对象是安加拉河左支流盆地：伊尔库特河，基托伊河，贝拉亚河，奥卡河，乌达河和比留萨河，并具有伊亚河流域的更详细特征。2019年的洪水是由先前潮湿的流域表面上的极端降水形成的。2019年，就洪水灾害特征和对图伦市的破坏性后果而言，出现了异常的水文状况。然而，在历史的过去和仪器观测期间，也再次发生了类似规模的灾难性洪水。在夏季发生两次极端洪灾的情况也不是唯一的。研究中的事件尚未与气候变化相关。即使考虑了2019年的最大径流量，峰值降雨径流序列的变化也几乎没有意义。以后一段时间内洪水频率的降低可能与到2019年结束的低水期有关。因此，