FORMATION PROCESS OF LANDSLIDE DAM RESULTING FROM LANDSLIDES AND DEBRIS FLOW

Abstract

Landslide dams are formed sometimes owing to the occurrence of landslides and debris flows. The present study discusses their formation and breach processes based on the numerical simulation of debris flows. The simulation model employs a depth-averaged two-dimensional form of governing equations which are composed of the mass conservation equations for the flow body, bed sediment and momentum conservation equations for the flow. Bed shear stress and erosion rate terms involved in the governing equations play important roles in debris flow behavior. Phase shifting phenomena from a solid phase to fluid phase is included in evaluating the mobility of debris flows. The numerical model is applied to the landslide dam formed within Ono River in Hita city after heavy rainfall in July 2017. The results suggest that the formation and breach processes of landslide dams are evaluated well by the numerical model.