Monitoring Mud-Flows for Investigative and Warning Purposes: The Instrumented Catchment of Rio Marderello (North-Western Italy)

Abstract

Mud-flows are natural phenomena that may occasionally occur in mountain torrents. They appear as waves with a steep front and a shape resembling that of debris-flows, but consisting of a muddy slurry that contains much less boulders and granular material than these latter. Nevertheless, mud-flows can cause severe damages to human settlements and infrastructures and may produce many casualties, as much as debris-flows do. The reduced boulder and debris content of mudflows may have an important influence on the results of the monitoring, which might be significantly different than those of debris-flows. This might be particularly true if seismic devices were employed as detecting tools, since the lack of huge boulders and large particles might impede the generation of strong ground vibrations. The ground vibration signals produced by mud-flows might also have different frequency ranges and different peak frequencies. These different behaviors should be investigated, not only for scientific purposes but also because they might lead to the choice of different parameters and algorithms in case seismic sensors were used for warning. For these reasons the Marderello basin, an alpine catchment prone to mud-flows located in North-western Italy, has been equipped with a micro-seismic network. The new monitoring system has been installed in the spring of 2013 and in July a mud-flow occurred that has allowed the collection of the first field data. These latter are presented in this paper together with a characterization of the catchment, a detailed description of the monitoring installations and an outline of future investigation plans.