Modelling for landslide area prediction in consideration of heavy rainfall event and soil water content in upstream catchment of dam reservoir

With increasing frequency of heavy rainfall events as a result of climate change, the long term assessment of sediment dynamics becomes a critical issue in maintenance and management of dam reservoirs. This paper discusses how heavy rainfall events in the upper basin affects sedimentation in a dam reservoir. A mathematical model was proposed in order to reproduce long-term changes of shallow landslide area in the test basin. The dataset of landslide area was obtained by aerial image analysis. It was assumed in the model that governing parameters of shallow landslide were intensities of the short- and long-duration precipitation, where the latter is deeply concerned with ground water content in the catchment. A threshold of shallow landslide occurrence was determined in consideration both of the short- and long-duration rainfall events. Applying the model to the Sagae Reservoir basin area in Yamagata Prefecture, the historical change of shallow landslide area was successfully reproduced by the model with higher accuracy than by the previous model7) in which the long-duration rainfall event was not considered. In addition, it was shown that the landslide area predicted by the present model was better correlated with the bottom sediment volume in the dam reservoir than the previous model.