| Accumulation and analysis of data on past slope disasters is important for national road slope management. We developed a database that includes information on about 1,300 slope disasters that occurred on Japan’s national roads from 1990 to 2004. Collected slope disasters are rockfalls, surface failures, rock mass failures, landslides, debris flows, and road surface anomalies. Using the database, road administrators can determine priority sections requiring countermeasures. Moreover, the use of GIS analysis, together with the database, clarifies the relationships between topographical and geological properties, rainfall and slope disasters. The results are summarized as follows:(1) More than 90% of slope disasters were caused by rainfall and only 2% by earthquake.(2) Surface failures constituted 81% of slope disaster forms. Road surface anomalies were next at 6%, followed by rockfalls and debris flows at 5% respectively.(3) The largest slope disaster was caused by rock mass failure, followed by debris flow.(4) Disaster-prone geology was generally Neogene green tuff and sedimentary rock, the so-called |
