Hydrogeological hazards and weather events: Triggering and evolution of shallow landslides

Abstract

Landslides are the most intense and serious manifestations of the degradation of slopes and they are the main causes of geological hazard when they, directly or indirectly, involving towns and infrastructures.They are a global environment problem; there are several examples that have produced untold damages and loss of human lives in many parts of the world. In 1920 the landslides mobilization, as a result of a strong earthquake in China, in the province of Kansu, killed 200,000 people; in 1938 fast debris flow, triggered by heavy rainfalls in Japan, caused the death of 600 people; in 1963 in Italy the Vajont disaster caused the death of 1,899 people, as a result of a landslide localized in the underlying artificial storage. During the last years there have been many tragedies linked to intense rainfall events which have sparked many shallow landslides: 1996 in Garfagnana, 1998 in Sarno, 2009 in the Ionic side of Messina, 2011 in Liguria. To throw light on this problem, over the past decades, the assessment and mitigation of landslides hazard and the danger related to it, have become goals of paramount importance in territorial planning and, more generally, in its management and with it the safeguard of the historical and cultural heritage within it. The occurrence of events which are considered exceptional thus implies a re-reading in terms of spatial planning to renovate the slopes and river-beds, as well as urban planning, infrastructural and socio-economic organization.The complex nature of these instability events that affect anthropized areas does not allow specific approaches for the defence of single good, but it finds a more effective solution based on the extensive knowledge of territory, perhaps at the scale of individual or several watersheds.