IAEG2006 Paper number 819 © The Geological Society of London 2006 1 Rainfall triggered flow-like landslides: Understanding from southern

Abstract: Flow-like landslides triggered by rainfall are very prominent in Nepal and Shikoku, Japan. In July 2002, many landslides occurred in the southern hills of the Nepalese capital, Kathmandu, because of torrential rainfall. A single flow-like landslide occurred at Matatirtha, a small village situated at the south marginal hill of Kathmandu, killing 18 people who lived at the foot of the hill. Much damage was caused to roads and houses because of landslides and debris flows in small streams. Similarly, in August, September and October 2004, strong typhoon hit the area of northern Sikoku, Japan and extensive damage occurred on hill slopes and some human casualties were also reported. Field observation showed that in northern Sikoku, many flow-like landslides occur in the thin weathering profile of igneous and sedimentary rocks, as well as in old debris materials. However, in the southern hills of Kathmandu, flow-like landslides occurred in weathered debris. During the investigation, the geotechnical properties of landslide materials were determined in the laboratory. The volume of material involved in some of the flows was calculated as per average thickness of the soil cover and area of failure. Likewise, rainfall threshold value for Kathmandu and Northern Shikoku is also evaluated. From the field investigations, it is recommended that human habitation at the foot of hills should be legally regulated by the government to reduce death from flow-like landslides triggered by torrential rainfall. I