Debris-flows in the Dolomites: Experimental data from a monitoring system

Field measurements of some dynamic properties of a channelised debris now were obtained from an automated monitoring system at Acquabona, Italian Alps. Ground vibrations, video-image analyses, and ultrasonic logs were used to obtain front velocity, instantaneous surface velocity and depth for three debris flows. All debris flows moved as a series of surges characterised by a steep coarser front having a curbing effect, followed by a more fluid muddy tail. Front velocities were always lower than instantaneous surface velocities and appeared to be affected by frictional resistance encountered by the front, and by slope and depth. Development of rigid plugs is not constant and appears related to changes in concentration of coarser particles during a single surge as well as between different surges of a same event. Also estimated Newtonian viscosities an indicative of variations in now characteristics during different stages of a debris flow and over a single surge.