Recent natural hazard events in Switzerland have demonstrated the destructive power of sudden landslides which continue to claim lives and cause substantial damage to property and infrastructure on an annual basis. TRAMM, a recently launched research project in the frame of the ETH Competence Centre for Environment and Sustainability (CCES), has the primary objective of investigating hydro-mechanical conditions for triggering rapid mass movements. In the core of the experimental part of the study a comprehensive hillslope observatory will be set up at Wiler (Lötschental, Canton Valais). Guided by comprehensive characterization of the site (soil, vegetation, hydrology, and geology) we propose to deploy banks of instruments (Time Domain Reflectometry (TDR), Electrical Resistance Tomography (ERT), capacitors) to provide continuous monitoring of hydrological conditions within the soil and rock on the hill-slope (water content and pressure dynamics), as well as local external conditions (temperature, precipitation, evaporation, wind, etc.). Innovative methods would be introduced for acoustic emission monitoring to detect root failure and initiating mass movement using commercially available sensors and newly developed units.
The present proposal seeks funding for instrumentation needed for establishing the first phase of such Rapid Landslide Observatory (RLO). The two primary factors affecting hillslope mechanical status are i) the spatial and temporal water content distribution, and ii) plant roots. Soil water content affects the hillslope mass and various mechanical properties including soil strength. We thus consider detailed monitoring of hydraulic pathways and water dynamics as a prerequisite for understanding hillslope failure behavior. We will monitor infiltration, redistribution of rainfall water and the exchange between soil and bedrock. We will employ Electrical Resistance Tomography (ERT) techniques to measure the three-dimensional water distribution supported by a dense array of pressure transducers equipped tensiometers to be installed at the soil/bedrock interface and across other critical interfaces and flow paths.
The stabilizing role of plant roots is well established, however, their modes of failure during rapid and extensive land movement are much less studied. We plan to capitalize on failure of these bio-fibers associated with soil movement using innovative acoustic emission sensor array presently under development. The funding request is limited to purchase of components to assemble these arrays.
The applied methods and instruments can be used in many other field studies of the involved institutes. It is of special interest in the framework of the SwissExperiment that is focusing of optimized self-sustained data collecting system. The experience based on the performed in-situ measurements will also be relevant for snow avalanche research.