Multi-temporal modeling of road-induced overland flow alterations in a terraced landscape characterized by shallow landslides

The presence of roads in high steep agricultural systems is often linked with landslides occurrence. This research aims to model multi-temporal overland flow dynamics in a shallow landslides-prone terraced landscape (northern Italy).The combined use of Remotely Piloted Aircraft Systems (RPAS) and photogrammetric techniques (e.g., Structure from Motion-SfM) allowed to elaborate multi-temporal high-resolution Digital Elevation Models (DEMs). Hydrological analyses of water flow’s depth alterations due to the road presence were carried out adopting the SIMulated Water Erosion model (SIMWE), focusing on different scenarios considering the presence of the road and assuming its absence through a specific DEM smoothing procedure. The possibility to perform multi-temporal hydrological simulations at a hillslope scale so as to analyse the role played by the road in overland flows alteration is still a challenge to be investigated. Results proved the role played by the road in water flows change above the two observed shallow landslides, with respective maximum water depth values equal to 0.18 m and 0.14 m. On the contrary, no-road simulations not revealed significant water flows deviations towards landslides, with water depth values around 0 m, underlining that the absence of the road would avoid relevant changes in water flow paths toward the collapsed surfaces. This work could be a solid starting point for analyse road impact on runoff dynamics and hillslopes stability also at a wider scale, as well as for planning efficient mitigation intervention so as to reduce the occurrence of similar future scenarios.