Identification and Estimation of Landslide Erosion Rate Based on Particle Swarm Optimization Algorithm

［Objective］ To construct a comprehensive multi-temporal landslide inventory across the Eastern Himalayan Syntaxis and quantify landslide-driven erosion rates, thereby revealing the geomorphological significance of landslide processes in this region. ［Methods］ The Particle Swarm Optimization (PSO) algorithm was employed to detect the change of the Normalized Difference Vegetation Index (NDVI) from remote sensing images, and a multi-temporal landslide inventory for the Eastern Syntaxis from 1987 to 2021 was constructed. The landslide erosion rate was calculated using an empirical landslide area-volume relationship. Additionally, the factors inducing landslide processes by considering climatic and topographic parameters were explored. ［Results］ A total of 1 323 landslides were identified in the study area between 1987 and 2021, with the highest occurrence of 389 landslides recorded between 2017 and 2021. The landslides predominantly occurred on both sides of the river valleys near the Yarlung Tsangpo River's Great Bend. The landslide erosion rates in the study area ranged from 0 to 76.06 mm/a, with an average rate of 0.44 mm/a. These rates showed a decreasing trend from the Great Bend section of the Yarlung Tsangpo River outward. The erosion rates were comparable to the exhumation rates of geological-scale rock bodies and the millennial-scale basin-wide average erosion rates. Landslide occurrences were associated with rainfall events and seismic activities, primarily developing on south-facing slopes and clustering within an elevation range of 1 500 to 3 000 meters and slopes of 35° to 45°. ［Conclusion］ Landslides represent the dominant erosion process in the Eastern Himalayan Syntaxis. Rainfall is influenced by the windward slope effect and concentrates on south-facing slopes, and drives the concentrated distribution of landslides on these slopes. Moreover, precipitation also triggers landslides by enhancing river incision, which steepens the adjacent slopes.