Movement pattern of debris flow

Abstract

A kinematic model is developed to estimate the velocity and runout distance of a gravitative debris flow. The characteristics and the different stages of development of a gravitative flow are first described. The equations governing the motion during the flow are then derived based on the Newtonian translation motion with some simplified assumptions on the erosion process along the flow path. After the motion is initiated, the debris is considered to behave as a frictional material with the friction angle during motion being a function of the distance travelled measured from the initiation point. The equations derived are applied to two well-documented case records to assess their applicability. The application shows that the computed runout distances are slightly higher than the measured values. This slight error on the safe side is consistent with the simplified assumptions used in deriving the equations. The small error is acceptable for engineering designs in areas vulnerable to debris flows.