SPATIO-TEMPORAL DISTRIBUTION PATTERN AND SUSCEPTIBILITY OF RESERVOIR-INDUCED LANDSLIDES IN XILUODU HYDROPOWER STATION

The reservoir-induced landslide is an important form of the impact of major engineering on geological environment and one of the frontier hot spots of research in engineering geology disciplines. Jinsha River Basin is located in the alpine gorge region at the eastern margin of the Tibetan Plateau, and has fragile geological environment and abundant hydro energy resources. It is one of the most densely built areas for hydropower plants and has 25 levels of cascade hydropower stations planned. However, the spatio-temporal effect of reservoir storage on reservoir bank reconstruction is still unclear. We took Xiluodu hydropower station as an example and study the distribution pattern of reservoir-induced landslides in the Jinsha River Basin. We use the multi-period remote sensing images from 2013 to 2020 to interpret the reservoir-induced landslides within the Xiluodu reservoir area. We finally acquire a total of 433 landslides. On this basis, we analyse the trend of the number and area of reservoir-induced landslides with impounding time. Subsequently, we statistically analyse the distribution of reservoir-induced landslides in relation to using the frequency ratio method. The six factors are elevation, slope, slope direction, engineering geological rock group, fracture and distance from dead water level. The assessment on susceptibility of each single factor was also carried out, and the reliability of the assessment results was verified by using the AUC method. And based on the evaluation results, four factors were selected to evaluate the susceptibility of reservoir-induced landslides. The four factors are elevation, distance from the fracture, slope and distance from the dead water level. The study concludes that:(1)Reservoir-induced landslides mainly occur during the initial 3-4 years of impounding, after which the number and area of landslides gradually decrease and the bank slope exogenetic reconstruction gradually stabilizes. (2)The range of slope and aspect that are liable to induce landslides are 30°~60°and SE, W, NW direction respectively. Landslide development is more favorable in the range of 400~3200 m from the fracture and 100~200 m from the reservoir area. (3)The AUC is 0.912, which proved that the evaluation result is highly reliable. (4)The main control factors of reservoir-induced landslide are the elevation and distance from the dead water level. The extremely high susceptibility area and high susceptibility area are mainly located within 400 m from the reservoir area and below 1 km in elevation. In this paper, a database of reservoir-induced landslides is established for the first time using multi-period remote sensing images, and the research results can provide support for the planning and construction of hydropower plants and disaster prevention and mitigation.