"풍화 산지에서 토사 재해 발생에 영향을 미친 요소들에 대한 연구 - 2020년 충청북도 북부지역을 사례로 -"

Abstract

Among the reports for damaged area by landslide in Chungju, Jecheon, and Danyang-gun in the northern region of Chungcheongbuk-do, where damage occurred due to heavy rainstorms from July 28 to August 11, 2020, the coordinates of the locations has been confirmed at 438 places. Analyses were conducted for those spots using the landslide information system of the Korea Forest Service, geological information from geobig data, KAKAO map, and satellite images from Google Earth. The most common bedrock in the affected area was granite, followed by gneiss, limestone and other sedimentary rocks, slate and phyllite. As for the slope, sedimentary rocks such as granite and limestone have the steepest slope, and gneiss, granite, slate and phyllite follows it. It seems that the impact by landslide on these types of rocks depended on slope and weathering pattern. The damage type examined in 375 sites out of 438 were due to erosion and sediment runoff from the slope, and debris flow occurred in 63 places. In 31 of them, it was found that the outflow of soil from the slope was connected to the debris flow. As a result of analyzing the rock types, most of the debris flow in the granite area appeared to be ‘runoff-dominant erosion’. It seems that ‘infiltration-triggered soil slip’ was strong in the limestone area. In this study, using Dynamic World, Google’s land cover change tracking service, surface cover changes were tracked between 2018 and 2021-2022 before landslide-related damage occurred, and it was found that small-scale vegetation changes in land use near the study area. It can be seen that changes in Korea’s forestry policy have had a significant impact on this. In particular, significant landslides have occurred after the considerable amount of time followed by anthropogenic change of vegetation and building of forest roads. Therefore, it seems that continuous management is essential to prevent landslide disasters after anthropogenic changes in land cover. In addition, field studies on the condition of soil weathering in mountainous areas and the process of material movement on slopes are essential.