The National Road RN 91 has been threatened for about twenty years by a huge rockslide, located 25 km south-east of the town of Grenoble, France. If several million cubic metres of rock fell down, the debris will dam the valley. Then the failure of the dam by overtopping and rapid erosion wouldresult in a catastrophic flood and dramatic consequences for human life, environment and economy throughout the valley. The paper presents the hazard estimation based on geological and hydrological surveys, and the risk evaluation and risk assessment that have been performed and the main prevention actions taken. A short range diversion of the RN 91 was constructed in the 90's. The daily risk management relies upon extensive monitoring of the unstable slope. Various solutions for a diversion of the river and fora new safe route of RN 91 are under study. For the covering abstract see ITRD E139491.
Samenvatting