Gypsum dissolution can be the cause of damage associated with subsidence and collapse.In Paris, the authorities want to refine the current maps of the areas likely to be affected by events. The mapping also revealed some sensitive areas that had not been previously identified; these will be checked by drilling. The constructed geological model and the hydrogeological analysis have already been used for studying other phenomena (e.g. sand flow and clay creep).

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(1) a maximum of 1.7 cm subsidence after the beginning of the water pumping (from the end of 1993 to mid 1995), (2) a stability phase during the water pumping (between 1995 and mid 19981. at last (3) an uplift phase (1.6 cm) after the end of the water pumping (from mid 1998). These results are coherent with the numerous geological and geotechnical data deduced from the monitoring of the water tables, or the levelling, and the field work done in that area.