Area of haeas clay soil

The removal by drying of clay soils during severe and/or long-lasting drought results in deformations of the soil surface (differentiated cutters). It can be followed by swelling phenomena as initial hydrogeological conditions recover or more rarely creep with softening. The purpose of the maps is to delimit all areas that are a priori prone to the phenomenon of withdrawal-inflating and to prioritise these areas according to an increasing degree of hazard: The areas where the withdrawal-inflating hazard is described as strong, are those where the probability of occurrence of a disaster will be the highest and where the intensity of the expected phenomena is the highest; Areas where the hazard is classified as low, the occurrence of disasters is possible in the event of a severe drought, but these disturbances will affect only a small proportion of the buildings (priority to those with construction defects or unfavourable local context, e.g. with nearby trees or heterogeneity of the basement); The medium hazard zones correspond to intermediate zones between these two extreme situations; The areas where the hazard is estimated a priori nil are areas where the current geological map does not indicate the presence of clay soil on the surface. It is not excluded, however, that some sins occur there, because there may be local veneers, interlayered lentils, slid piles at the foot of the slope, or tampering pockets, of a clay-like nature, not identified on the geological maps at a scale of 1:50,000, but whose presence may be sufficient to cause occasional disturbances.