Abstract
Remote sensing data offer an accurate source of information to the administration. Walloon administration develops its capacities in using Earth Observation data to respond to the EU request of characterizing the risks related to closed and/or abandoned mining sites. This paper compares two Digital Elevation Models (DEM) derived either from aerial photos or from a LiDAR (Light Detection And Ranging) scanner in their capabilities of characterizing unstable land cover and risks of landslides for Walloon coal waste heaps.

The DEM from LiDAR data offers a resolution of 1 m. It leads to significant differences in the spatial and statistical distributions of slopes, as compared to the regional 10 m-resolution DEM. To test this spatial effect, the resolution of the LiDAR DEM has been averaged by pixel aggregation to 2/4/8 and 10 m - resolution for direct comparison with the ERRUISSOL DEM. In all cases, the application of the geotechnical factor of safety criterion based on the high-resolution LiDAR DEM leads to larger portions of heap surfaces at risk of geotechnical failure. In the next months, this method will be proposed to the Walloon administration for application to all facilities considered at risk by the first inventory to improve the characterization of the risk of geotechnical failure, and confirm or not the risk.