Debris Flow Hazard In Tasmania, Australia

Colin Mazengarb, Claire L. Kain, Nicholas J. Roberts and E.H. (Ted) Rigby

Debris flow hazard in Tasmania has been largely under-appreciated until recently, and accordingly, emergency management plans are in the early stage of formulation. In this study the geological, historical, and contemporary evidence for debris flow processes in Tasmania is reviewed. From a landslide inventory, a geomorphic process rate with a derived magnitude-frequency power-law relationship was calculated in order to estimate event volumes, which are then used to derive input for numerical simulations. Specialised debris flow runout software was employed to predict at-risk areas in a similar fashion to standard design-event flood modelling practice. The rheological parameters chosen for each model were based on calibration with a limited number of past events. However, this small calibration dataset revealed contrasting properties, and our simulations represent a ‘worst case scenario’ within a spectrum of possible flow behaviours. Finally, the communications processes being used to share these results with Tasmania’s emergency management community is discussed.