H12. 9東海豪雨による流木の調査

抄録

On September 11th and 12th, 2000, a heavy rain attacked the Takai district. The upstream of the Yahagi River basin was also suffered from huge damage. The flood due to the rain accompanied large amount of driftwood which covered the Yahagi Dam reservoir. This report is on the investigation of driftwood picked up from the reservoir. Characteristics of the driftwood such as kind of tree, shape, age and so on are investigated and compared to those of an artificial forest in the Yahagi Dam basin. Japanese cedar is dominant in the driftwood, while Japanese cypress is in dominant in the forest. The age of the driftwood is relatively younger than the forest one. The sources of the driftwood are classified into live trees and cut ones by thining. It is shown that the latter, which have been considered major source of the driftwood, is just about 20 %. It is concluded that effective countermeasure should be conducted in order to prevent live trees from drifting.