Mapping permafrost at a regional scale: interpolation of field data by using GIS in the Upper Durance catchment (Southern French Alps)

International audienceSouthern French Alps are mostly non-glaciated areas, but permafrost was locally evidenced at high altitudes (above 2800 m.a.s.l.). A clarification of permafrost spatial extent is currently needed because it constitutes a water resource. We suggest here a new method to map the permafrost. This method is based upon water temperature measurements, providing many observations (presence or absence) about permafrost in various physical settings. Such point-based data are integrated in a spatial database to realize an interpolation of the presence of permafrost. The study area is subdivided in many classes according to the incoming solar radiation. For each class, two thresholds are specified, one above which permafrost can possibly be observed, the other one above which permafrost can probably be observed. This method seems to complete previous models which were mostly based upon rockglacier inventories or BTS measurements. A map of permafrost extent is proposed, showing that it may possibly occur above 2500 m.a.s.l. in highly shielded areas. Some ice may be still stored within some footslope deposits, constituting a possible water resource