The Morgex avalanche - a comparative study

On February 23, 1999, in Morgex (Aosta, Italy) a large mixed avalanche was released from the basin of the Lavanchers torrent. Its powder part reached to the opposite side of the valley, caused whereas the dense part stopped at 975 m a.l.s. with a volume about 500.000 mc and a thickness close to 8 m. It was described by observers as a high cloud almost 500 m hight. One house, the phone and power lines and portions of wood (400000 mq ) were destroyed; a number of buildings were damaged and there was even one victim. The paper presents a comparative estimation of the powder avalanche behaviour and of its impact pressure by means of three different numerical approaches: • a back analysis based on the structural damage observed; • a one-dimensional depth-averaged mixed flowing/powder snow avalanche model developed at SLF-Davos; • a one-dimensional depth-averaged flowing snow avalanche model based on a Navier-Stokes modified equation developed by Studio Ceriani. This paper demonstrates that two different snow avalanche simulators can give the same results about the avalanche run-out, flow velocity and the definition of the avalanche hazard cartography, in according with the data and information obtained by the structural damage observed