Rapid landslides threatening roads: Three case histories of risk mitigation in the Umbria region of Central Italy

The geomorphologic and geologic characteristics of the Umbria Region of central Italy, along with its urbanization, are the main cause of the widespread landslide risk. In the region, landslide risk is classified in a ranking between I and 4, where 4 is for the highest level. Shallow landslides, debris flows and rock-falls are included in this highest level, since they are extremely rapid and intense. Many of these typologies of landslide recently occurred in the Umbria Region of Central Italy affecting the major road network. Pilot study areas were selected within the Region where important transportation corridors lie in the zone threatened by rapid landslides. This paper describes the risk mitigation strategies adopted for the selected roads and introduces the crucial issue of the residual risk management. By presenting different situations, this paper shows how the regional authorities faced the problem, and tries to summarize the answer that they gave to the issue by combining countermeasure, information and maintenance actions.