Rainfall threshold-governed landslide susceptibility in the Himalaya

Study Region The Himalayan range. Study Focus This study develops a coupled modeling approach that integrates I–D thresholds and an optimal model to evaluate landslide susceptibility across different rainfall intensities. New Hydrological Insights for the Region The cumulative antecedent rainfall during the 168 h preceding landslide events exhibits a sublinear power-law relationship with landslide frequency in the Himalaya. The 5%–90% threshold curves show a decreasing trend in intensity with increasing duration. Driven by complex orographic precipitation, the overall pattern of landslide susceptibility in the Himalayas is characterized by higher values in the southern regions and lower values in the northern regions, with spatial variations across the eastern, central, and western sectors. Furthermore, coupled modeling demonstrates that regional landslide event is highly sensitive to rainfall at different quantiles. When the threshold rises from 5% to 90%, the area of very low susceptibility decreases by nearly 50%, while the area of very high susceptibility increases markedly to 17.95% at the 90% threshold. By integrating rainfall thresholds with landslide susceptibility models, this study provides critical hydrological insights into how landslides respond to diverse rainfall conditions across complex terrains, offering a robust scientific basis for regional landslide susceptibility assessment under different rainfall scenarios.