Damage and Restoration of Roads by Prolonged and Enlarged Volcanic Disaster of Mt. Fugen in Unzen

Mt. Fugen in Unzen erupted November 17th 1990 after 198 years of silence. Residents of Shimabara city were forced to evacuate their homes due to debris flow of Mizunashi River, which is located below Mt. Fugen. Pyroclastic flow-a very fast moving mixture of gas and rocks claimed the 43 lives on June 3rd. The volcanic disaster of Mt. Fugen are prolonged and enlarged more than four years. Disaster prevention officials of roads recognized the danger of the mountain erupting and considered a counter- plan to protect their facilities. They also considered emergency and permanent restoration plans after debris flows and proclastic flows attacked roads. In this paper, emergency counter plan, damage and both temporary and permanent restoration plans of roads to volcanic disaster of Mt. Unzen are reported and discussed. Problems which now have to solved as well as some lessons to be learned are also explaned