Calibration of a runout prediction model for debris-flows and avalanches

A simple numerical model for the dynamic analysis of unsteady flow is being systematically calibrated through the back-analysis of a variety of debris flow and avalanche case histories from several regions including Hong Kong and British Columbia. The model allows the selection of a rheological relationship which defines the flow resistance. The results to date indicate that most debris avalanches on open slopes can be simulated satisfactorily using a frictional model with pore-pressure conditions that are intermediate between fully drained and liquefied. Channelised debris flows involving the dilution of debris by water and/or the entrainment of liquefied saturated material appear to conform best to a frictional-turbulent model. Through the back-analysis of several case histories, relationships between slope properties and model input parameters are emerging, These relationships will allow a typological classification based on the pre-failure slope properties, which will in turn provide a reliable method for prediction of the runout characteristics using the dynamic model.