Shallow landslide analysis based on topographical segmentation using stream‐tubes

Daizo TSUTSUMI, Rinto KOSHI, Kazuki YAMANOI and Masaharu FUJITA


Shallow landslide is one of the major causes of sediment related disasters in Japan. To mitigate damages caused by sediment disasters, predicting shallow landslides might be an effective countermeasure. Numerous studies have been conducted to predict shallow landslides by physical, empirical and statistical approaches. The authors have also tried to predict shallow landslide occurrence employing numerical simulation combining computations of rainwater infiltration and slope stability by critical slip surface analysis method, which can precisely specify a shape of slip surface. However, the critical slip surface method has been able to be applied only to a single slope area hitherto. In the present study, to extent the applicable area of the critical slip surface method from a single slope to a watershed, we employed stream tubes instead of rectangular grid to divide the watershed area into individual tubes and elements. The Okanazawa watershed in Izu‐Oshima, where shallow landslides and debris flows took place in 2013, are divided by the stream tubes and the critical slip surface method are applied to all individual stream tubes to reproduce the shape, location and timing of the shallow landslides. The results demonstrate that the present method simulates the location of the shallow landslides quite accurately comparing to the conventional analysis by assuming infinite slope, although the timing of landslide occurrence is not well simulated. The present method can be potentially improved employing more reliable rainwater infiltration analysis method. Further investigation is needed to evaluate the applicability of the method to watersheds with different geological and topographical characteristics to use the present method as a practical countermeasure for mitigation of the sediment related disasters.

Key words

shallow landslide prediction, critical slip surface analysis, stream tube, Izu‐Oshima, numerical simulation