An empirical-statistical model for debris flow travel distance

Abstract

An empirical model is presented for analysis of debris flows based on field observations of landslides from clear-cuts in the Queen Charlotte Islands, British Columbia. Given an initial failure volume, changes in event magnitude arising from entrainment and deposition along the path of movement are used to establish the point at which the cumulative flow volume diminishes to zero, and therefore the total travel distance. Hillslope morphology is used to assign three types of flow behaviour: unconfined, confined, and transition flow. Flow behaviour and slope angle determine the occurrence of entrainment or deposition in the model, for every reach of the event path. Volume change in a reach is calculated from regression analysis of the Queen Charlotte Islands field observations. Predictor variables are reach length, width (of entrainment and (or) deposition), and slope angle, together with a bend-angle function and the incoming flow volume.Key words: slope stability, debris flow, travel distance, runout, risk, clear-cut.