Application of SOSlope to shallow landslide triggering in Rüdlingen (Switzerland)

The development and application of deterministic models for vegetated slope stability analysis at a local scale is a pivotal issue in international research. Such tools identify mitigation and risk management techniques during increasingly frequent critical rainfall events. In this sense, the SOSlope software, developed by ecorisQ international association (www.ecorisq.org), allows the simulation of hydro-mechanical dynamics that may influence shallow landslides' occurrence, focusing on the progressive activation of root reinforcement in space and time to counteract soil movement. 

This study presents a reconstruction of an artificially triggered landslide in Rüdlingen (Switzerland), carried out during the Triggering Rapid Mass Movements project, aiming for a back-analysis of the hydro-mechanical conditions leading to its triggering. This experiment allows comparing real-scale data on triggering dynamics of shallow landslides with modeling assumptions and results. Detailed measurements during the investigation and following slope failure were used to calibrate the hydro-mechanical input parameters used in SOSlope and evaluate the modeling capability to reproduce the landslide-triggering conditions and behaviors. 

Results show a reasonable reconstruction of the complex dynamics leading to the loss of soil stability. In particular, considering the water effect and the force redistribution dynamics during the triggering. SOSlope can quantify the effect of the root reinforcement spatial distribution and passive earth pressure. In addition to quantifying the maximum value of root reinforcement achieved to counteract soil movement, SOSlope enables observing its progressive activation in space and time. Pore water pressure dynamics show a distinctive trend regarding preferential flows in soil fractures and macropores; the decrease of suction stress due to increased water content in the soil matrix was also observed. SOSlope allows for systemic analysis of the landslide event by evaluating the different phases of change in slope stability and identifying the causes that favored their failure. These results are challenging to understand the shallow landslide triggering dynamics on vegetated slopes, given simplified assumptions through simpler models. This tool could support risk management strategies, including green-based solutions, nearby structures and infrastructure, or reforestation activities for slope stabilization. In the latter case, through the software, the structure, composition, and efficiency of the plantation can be checked. 

Future developments in SOSlope will include the implementation of a triangulated grid mesh to improve computational limitations associated with the raster input data square grid resolution and the inclusion of new tree species for root reinforcement estimation.