Acquiring, sharing and exploiting long-period and multi-parametric instrumental data for landslide science: the French EPOS-France vision, and its implementation at the European level.

Documenting landslide activity over long periods using monitoring standards (sensors, acquisition rates, quality-control) is critical for understanding landslide forcing factors, validating process-based models, identifying the effect of climate change on their behavior, and ultimately defining warning thresholds. These goals underline the mission of the Thematic Group “Landslides” currently being set up among several French institutes (CNRS, BRGM, CEREMA, IRD) within the national Solid Earth Research Infrastructure EPOS-France.The thematic group has two objectives organized in two Specific Actions (SAs): SA#1 - setting up a permanent observatory of continuously moving large landslides using a multi-instrumented approachSA#2 – setting up an observatory of landslide hot moments, corresponding to monitoring campaigns of specific landslide acceleration periods in order to learn from such specific extreme events.The two SAs are built upon the sensor technologies and information system of the French Landslide Observatory (Observatoire Multi-Disciplinaire des Instabilités de Versants) which is a service of the French Research Institute (CNRS) in charge of deploying, acquiring, exploiting and disseminating multi-parametric sensor data over several large landslides. OMIV has developed, since nearly 20 years, standards in terms of sensor types, using both high-grade and low-cost sensing in order to construct reference and spatially dense monitoring time series. The service provides open access to records of landslide kinematics, landslide micro-seismicity, landslide hydro-meteorology and landslide hydro-geophysics. Combined, these categories of observations are unique worldwide for long-term landslide observations. OMIV is currently supervising the acquisition and dissemination of sensor data on 8 permanent unstable slopes (Avignonet/Harmallière, La Clapière, Séchilienne, Super-Sauze/La Valette, St-Eynard, Pégairolles, Vence, Villerville) and on unstable slopes currently experiencing gravitational crises (Viella, Marie-sur-Tinée, Aiguilles). The service is organized around the dissemination of qualified data (in international reference file format) and products for 5 categories of observation (Geodesy, Seismology, Hydrology, Meteorology, Hydrogeophysics). For each category of observation, specific FAIR data repositories and access portals are available and automated processing methods have been proposed to meet the needs of the landslide research community. The products being generated are time series of GNSS and total station positions, catalogue of endogenous landslide micro-seismicity, resistivity tomography datasets, and hydro-meteorological parameters. These observations aim at contributing at identifying the key controlling parameters of different landslide types (e.g. soft/hard rock, cohesion/friction, slip/fracture, localized/diffuse damage) and at monitoring their evolution in time and space (deceleration or acceleration according to the triggering factors, sliding- flowing transition).The objective is to present the strategy of data acquisition, qualification, dissemination and exploitation of the EPOS-France landslide thematic group, and discuss ideas to set up (at mid-term) a European landslide thematic core service (landslide-TCS) within EPOS ERIC.