Investigating the interaction between snowmelt runoff and road in the activation of hillslope instabilities affecting a landslide-prone mountain basin through a multi-modeling approach

Roads presence and landslides occurrence in steep slope mountain areas are often strictly connected. In recent decades, the use of Airborne Laser Scanning (ALS)-derived high-resolution topographic data amplified the possibilities to better represent landscapes and related physical processes at the basin scale. Additionally, the adoption of topographically-based hydrological models allows to simulating water overland flows dynamics and investigating the occurrence of specific degradative phenomena. In this regard, snowpack melting plays a key role in altering superficial water dynamics in mountain landscapes, but accurate investigation about the interaction between snowmelt runoff and human infrastructures (such as roads) in the occurrence of hillslope failures is still obscure. This research aims to assess the relationship between snowmelt runoff, road presence and terrain instabilities affecting a landslide-prone steep slope mountain meadow (northern Italy). An innovative multi-modeling approach was tested to detect the alteration of snowmelt overflows due to the road’s presence, as well as to investigate its relationship with the activation of a shallow landslide. The role of the road in altering snowmelt runoff was investigated both considering its presence and assuming its absence by a novel Digital Elevation Model (DEM) editing procedure. Different hydrological and slope stability models were interactively implemented, starting from pre-event ALS-derived DEM to propose predictive basin-scale simulations. Results attested the relevant role played by the road in altering snowmelt runoff overland flows, as well as their combined contribution in the foreseen activation of the observed shallow landslide. Starting from on-field observations conducted after the landslide triggering, the accuracy of instabilities predictions was tested through the computation of the Area Under the Receiver Operating Characteristic curve (AUC-ROC) and the Cohen’s kappa-index. This work could be a useful tool for planning mitigation interventions able to reduce the occurrence of similar risk scenarios, also providing specific suggestions for developing and promoting efficient sustainable actions for mountain landscapes.