Water infiltration and the resultant transient changes in the hydrological systems are the most common triggers of landslides. Because of the large variability in the quantity of water stored in the soils, the buffering capacity of the vadose zone, and the comparatively few return periods of critical rainy episodes, the behaviour of many unstable slopes is mainly controlled by hydrological processes.

There are different types of hydrological triggering mechanisms dependent on the state of the system which defines the thresholds for first-time failure and landslide reactivation. These hydrological mechanisms, like pore water increase or matric suction decrease, are reasonably well incorporated in geomechanical models. However, the incorporation of hydrological process knowledge in slope failure analysis still lags behind, whereas the importance of it has been recognized already long time ago by the landslide community. The research frontiers are connected with the complexity of real landslides, the difficulty to monitor groundwater levels or soil moisture contents in unstable terrain, and the difficulty to understand the water pathways within fine grained or clayey soils which are the characteristic substratum in which landslides occur.

This session aims to discuss innovative process research within landslide studies to improve our understanding of the spatio-temporal patterns of slope movement mechanisms.

We invite research ranging from unsaturated zone, hillslope processes and regional hydrology which are applied to landslide research in a broad sense: ranging from soil slips to large scale slope deformation. The session will give time to both laboratory and field observations. We especially invite innovative studies to determine spatial heterogeneity of water flows in the subsurface, water tracing and travel time distribution. Lastly, we invite pioneering research which includes the hydrological processes knowledge in the geotechnical analysis and modelling that sets the next step to improve landslide hazard analysis.