Geologic controls and rainfall thresholds for landslide occurrence in northern Vietnam

In the mountainous areas of northern Vietnam, many landslides occur every year during the rainy season and typhoons. Landslide damage has affected many villages and mountain slopes, such as road slopes and terraced rice paddies, in relation to recent climate change and rapid development in Vietnam. Therefore, there is an urgent need to establish an early warning evacuation system for landslides. However, the construction of a highly accurate landslide warning system remains difficult because of insufficient data on the factors affecting landslide occurrence, such as rainfall, geology, and groundwater. The objective of this study is to clarify the relationship between landslide occurrence and geology, geological structures, and rainfall in northern Vietnam, based on detailed data reported from the State-Funded Landslide Project, a Vietnam-funded landslide project started in 2012. Research has revealed that the scales, types of movement, and distribution of these landslides are strongly affected by the geology, geological structure, and weathering of rocks. An outline of the relationship between precipitation and landslides was also obtained. These results are useful indicators for determining future landslide hazard areas and thresholds for warning and evacuation systems.