Numerical modelling of catastrophic events produced by mud or debris flows

Abstract

Mud and debris fl ows are natural phenomena representing serious hazard for population and structures in mountain zones, because of their rapid occurrence and the diffi culty in forecasting the phenomena initiation. Numerical models can however be useful in predicting the peak discharge and the strength of fl owing mass, helping administrations in preparing risk mitigation measures. In this work, a numerical model for hyperconcentrated fl ows is presented. It is based on shallow water equations, with a particular source terms treatment which translates into an increased numerical stability and makes the model highly versatile. The test case applications focus on some fundamental characteristics necessary for debris- and mud-fl ow representation. In particular, classic dam-break problems have been used to test wave celerity and wet-dry fronts propagation, while a mud-fl ow dam-break problem has been chosen to investigate model sensibility to different rheological schemes. Then, the model has been applied to two real events that occurred in Northern Italy. The fi rst one is a debris fl ow which took place at Acquabona, near Cortina d’Ampezzo. This event is extensively documented, since it has been observed by a monitoring station prepared by the University of Padua. The second one is a tragic event, during which the little town of Stava has been stricken by a destructive mud fl ow caused by the collapse of two earth dams.