RESEARCH ON SLOPE FAILURES INDUCED BY FLOOD IN AUGUST 2003 IN NUKABIRA RIVER AND ITS CAUSES

Abstract

A heavy rainfall caused by a stationary front vitalized from season’s 10th typhoon occurred in southeastern part of Hokkaido Japan on August 8 to 10, 2003. The 48 hour total rainfall at the Biratori observation point catchments recorded 306.2mm was the largest precipitation in the last 41 years. During the event, huge amount of sediment and drift wood had been provided from the upstream of Nukabira river basin. Based on field investigation and remote sensing data analysis after the event, and also analysis of contributing factor of slope failure such as rainfall amount, slope angle, vegetation and geological conditions, it was made clear that 1) the slope failure area were increased by about 3.6 times that of 2002; 2)the slope failure event strong related with hourly rainfall.