Hydrogeology of the Area
Research Studies by T. Lebourg and B. Fresia, Geoazur, UNS, Nice, France.

Thursday 10 December 2009 by Thomas Lebourg

traduction [English ] [français ]

The Vence village is encompassed into a large catchment spreading from the Baous zone north-westerly until the Cagne River easterly. The catchment includes the Jurassic to Oligocene series that shapes the Vence anticlinal and inside which a captive deep groundwater limited at its base by the impermeable Keuper can be observed. Besides, the Prat de Julian is included inside an unconfined secondary groundwater associated to the sandy formation of the Lower Eocene (see the following figure).


Hydrogeological cross section of the Vence catchment

The observation of the underlying Cretaceous and Jurassic limestones indicates a fracture porosity and a karstification allowing the formation of a deep watertable. The sandy table is created by the difference in porosity between sands and limestones, the natural porosity of the sand being well superior to the fracture porosity of the substratum. The watertable is revealed by the numerous observed springs at the landslide base and by contact between limestones and sands.

Moreover, the studies carried out by Simecsol and the piezometers settled on the field put forward a homogeneous groundwater storing waters at the top of the landslide and flowing down to the Lubiane River.

The fracturation of the massif and the coexistence of the two tables show the possibility of communication through the limestone mass, by the fault and karst networks. On the field, water is present at the bottom of the slope in the form of springs and in the form of reemergence stagning at the surface during rainy seasons.