When Climate Change Affects Rainfall, Landslide Frequency Responds: An Assessment at the Subregional Scale

This study presents a methodological framework to assess climate change impacts on the hydrological conditions leading landslide occurrence. The approach is applied to a ~170 km² landslide-prone area in southern Italy, characterized by complex topography and rainfall-driven slope instability. Regional climate projections from CORDEX for the period 2006–2070, under moderate (RCP4.5) and high (RCP8.5) emission scenarios, were bias-corrected using observed rainfall data (2006–2023) and evaluated against a synthetic dataset representing present-day climatic conditions.

Aiming at event-scale detection of rainfall-triggered landslides throughout the study period, soil hydrological processes were simulated using physically based models and coupled with slope stability analyses that account for unsaturated soil behavior. Scenario-based statistical comparisons were carried out across three rainfall-homogeneous subregions. The analysis reveals a general trend toward drier conditions, in line with regional climate projections, together with enhanced rainfall variability at the subregional scale. Nevertheless, landslide occurrence is projected to increase significantly in climate change scenarios, with a more pronounced rise under RCP4.5 compared to RCP8.5.

This apparently counterintuitive response reflects contrasting changes in rainfall and landslide dynamics. Under RCP8.5, landslides are mainly triggered by more intense rainfall events, whereas under RCP4.5 they arise from the combined influence of wetter antecedent soil conditions and more intense early-peak rainfall. These results underscore the persistent and critical role of antecedent soil moisture in landslide initiation, even under rapidly evolving climate conditions.