Abstract—

This article presents an analysis of the current forest conditions and their water-regulating effect on the development of flash flood events using the Iya river basin as an example, where a catastrophic flash flood occurred in June and July 2019, which resulted in great damage and fatalities in the Tulunskii district of Irkutsk oblast. The methods include spatial-temporal analogies, mathematical-statistical analysis, aerospace monitoring and field geobotanical interpretation, and cartographic modeling. The main indicators that reflect the water-regulating functions of the forest, such as forest cover, bonitet, degree of crowding, and the species and age composition of woody stands are considered in terms of their dynamics for 2008–2018. We examine the main factors that lead to impairment of the water-regulating functions of the forest, including fires, clear-cutting, and damage caused by pest insects and diseases. Results of the Landsat 7 and Landsat 8 image analysis and from field work were used to compile a map showing areas with primary and disturbed vegetation communities, as well as other artificially transformed territories (agricultural land, spoil tips, and other accumulated spoil, settlements, etc.). It was determined that the most disturbed communities are located in the plain and most developed subtaiga forest vegetation provinces are represented by secondary small-leaved stands with a significant inclusion of large-contour agricultural land (primarily, arable). The main conclusion of the study suggests that the considered forests are in satisfactory condition in terms of their quality characteristics and adequately fulfill their water-regulating functions. The existing degree of disturbance of the forests did not contribute to an increase in the flash flood, since the latter was determined by the abnormally heavy and long-lasting precipitation and orographic features of the watershed. The part of the area located in the subtaiga province, however, requires reforestation on unused agricultural land due to its lower forest cover and large-scale human activity.

中文翻译：

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森林条件对伊尔库茨克州2019年夏季山洪形成的影响——以伊亚河流域为例

摘要-

本文以伊雅河流域为例，分析了当前森林状况及其调水作用对山洪暴发的影响，该流域在 2019 年 6 月和 7 月发生了灾难性山洪，造成了巨大的破坏和损失。伊尔库茨克州图伦斯基区的死亡人数。这些方法包括时空类比、数理统计分析、航空航天监测和野外地质植物学解释以及制图建模。2008-2018年，反映森林调水功能的主要指标，如森林覆盖度、毛冠、密集度、木本林分树种和年龄组成等，是根据其动态变化考虑的。我们研究了导致森林调水功能受损的主要因素，包括火灾、伐木和病虫害造成的损害。Landsat 7 和 Landsat 8 图像分析和实地工作的结果用于编制地图，显示原始和受干扰植被群落的区域，以及其他人工改造的领土（农业用地、弃土点和其他堆积的弃土、定居点、等等。）。确定最受干扰的社区位于平原，最发达的针叶林植被省以次生小叶林为代表，其中大量包含大轮廓农业用地（主要是耕地）。研究的主要结论表明，所考虑的森林在质量特征方面处于令人满意的状态，并充分发挥了其调水功能。森林现有的干扰程度并没有导致山洪暴发的增加，因为山洪暴发是由异常强且持续时间长的降水和流域的地形特征决定的。然而，位于 subtaiga 省的部分地区由于森林覆盖率较低和大规模人类活动，需要在未使用的农田上重新造林。