Quantitative hydrogeology in the Tevere River basin management planning (central Italy)

Abstract

The paper deals with a methodology to assess the landslide hazard along rivers on the basis of geological and hydraulic conditions, recognized as critical. As an example, the methodology was applied in the middle Trebbia Valley (Northern Italy) where slopes are characterised by several landslides and the Trebbia River, often braided, curves “weak rocks” (OLIVEIRA, 1990). First the geological and geomorphological setting of the area was analysed, with particular reference to the evolution of the river-bed and to the location of those areas subjected to landslides. Then, the hydrologic and hydraulic study of the River allowed to determine both flood contours and shear stress for erosion. A correlation between the fluvial dynamic and the slope stability near by the river was identified comparing the hydrologic and geologic critical conditions. To validate this correlation, the geomorphologic instability indicators were surveyed and then they were used to improve the landslide hazard map. Finally, a specific area (Barberino gorge) was studied, to point out that the flood events can produce important shear stress for erosion, accelerating the erosion at the slope foot; therefore the landslide progresses from the bottom to the top.