Abstract
Torrential rains in Fukui, July 2004 resulted in heavy damage to ground in the Asuwa river basin. This paper reports an outline of the matters and causes of the following damage: 1) The dike in the lower reaches of Asuwa river was breached in city area. A detailed survey was undertaken to determine why the dike was breached at that location. 2) Many cases of damage to revetments were observed in the upper reaches of Asuwa river and its tributary streams, and the damage was worsened by inundation resulting from timber debris and sedimentation. There were many cases of slope failure above revetments, which were thought to be due to scouring. 3) Many slope failures occurred at locations distant from rivers. In many cases they were relatively shallow collapses. 4) Many mud and debris flows occurred along small rivers or in mountain valleys, and large quantities of mud and timber were displaced. 5) At five steel bridges on the JR Line, bridge girders were washed away and bridge supports collapsed or were damaged. Considerable damage was caused to road bridges and to road and rail embankments. Our survey team carried out investigations into these 5 types of damage, to grasp the full extent of the damage and establish issues for future consideration.
