INFLUENCE OF FOREST CONDITIONS ON THE FORMATION OF THE SUMMER FLOODS IN IRKUTSK OBLAST IN 2019 (A CASE STUDY OF THE IYA RIVER BASIN)
E.L. MAKARENKO1, A.P. SOFRONOV1,2
1V.B. Sochava Institute of Geography, Siberian Branch, Russian Academy of Sciences, 664033, Irkutsk, ul. Ulan-Batorskaya, 1, Russia
2Pedagogical Institute, 664011, Irkutsk, ul. Nizhnyaya Naberezhnaya, 6, Russia
Keywords: forest cover, flooding, water-regulating function of forests, precipitation, disturbance of forests, mapping
Abstract
An analysis is made of the current forest conditions and their water-regulating effect on the development of flood situations using, as an example, the Iya river basin where a catastrophic rainfall flood occurred in June and July 2019, leading to great damage and human casualties in the Tulunskii district of Irkutsk oblast. The methods of spatial-temporal analogies, mathematical-statistical analysis, aerospace monitoring and field geobotanical interpretation, and cartographic modeling are used. The main indicators reflecting the water-regulating functions of the forest (forest cover, bonitet, degree of closeness and the species and age composition of tree stands) are considered in terms of their dynamics for 2008-2018. We examine the main factors leading to an attenuation of the water-regulating functions of the forest: fires, felling and damage caused by pest insects and diseases. Results from analyzing Landsat 7 and Landsat 8 images and expedition-based investigations were used to compile the map displaying the territories with primary and disturbed vegetation communities as well as other anthropogenically modified territories (agricultural land, spoil heaps and refuse dumps, settlement territories, etc.). It was determined that the most disturbed communities are located in the flat and most developed, subtaiga forest provinces and are represented by secondary small-leaved stands with a significant inclusion of large-contour agricultural land (primarily arable land). The main conclusion of the study indicates that the forests of the territory, in terms of their quality characteristics, are in satisfactory conditions and adequately fulfill their water-regulating functions. The existing degree of disturbance of the forests did not contribute to an increase in the flood, because the abnormally abundant and long-lasting precipitation and the orographic features of the catchment basin served as its determining factors. However, a part of the territory located in the subtaiga province, due to its lower forest cover and active anthropogenic activity, needs reforestation on unused agricultural land.
|
