Coastel erosion monitoring by means of geophysical methods

One of the most frequent problem in the islands is given by the erosive coastal process, due to the atmospheric agents and to the wavy motion. Moreover human activities favor and accelerate the modifications of the sea tides and the superficial erosive processes. Often, in fact, the losses from water-pipes or the construction of buildings and roads, modify soil structure, limiting and varying the natural groundwater flow and exposing the most alterable rocks to the action of erosion by waters and winds. In the present work the “physical condition” of the Promontory of Balai (Sardinia-Italy) is examined (fig.1). This zone is exposed to predominant winds in the island and wavy motion. Recently the construction of docks, near the harbour of Porto Torres, has produced acceleration of the erosion phenomena. The area is of particular interest for the presence of an old church (S. Gavino a Mare, XI a.C.) and for a built-up village. The final aim was to establish the sinking and settling risk. In order to know the evolution of the erosion phenomena in the inner part of the promontory, boreholes, electrical tomographies, seismic tomographies and a microgravimetric survey, have been executed.