Abstract
Abstract. To set an approach for the future territorial planning, the Geological Survey of Friuli Venezia Giulia Region, through the researchers of Trieste University, started a program of debris-flow risk analysis using Flo-2D software as tool to delimit the hazardous areas. In the present paper, as a case study, a debris flow, called Fella sx, occurring in a torrent catchment was analyzed. The choice was due to the abundance of information about past events, inundated areas, rain fall, geology and to its representativeness. An initial back-analysis investigation identified a couple of representative rheological parameters. Riverbed samples were collected, sieve analyses were performed and rheological tests were carried out on the fraction finer than 0.063 mm using a rotationally controlled stress rehometer equipped with the serrated parallel plate geometry. The shear dependent behaviour was examined at different concentrations ranging from 33 to 48%, by weight. Viscosity data treatment was performed to determine the most suitable rheological model to provide the best approximation of the debris-flow behaviour. The rheological parameters, derived from experimental data, were used and compared with those obtained through the back-analysis and with the real inundated area. Data obtained through rheological analysis are useful in constructing scenarios of future events where no data for back-analysis are available.
Highlights
Debris flows are one of the most dangerous and destructive processes that concern mountain areas (Cavalli et al, 2005)
The material involved in the occurred debris flow is produced by erosional phenomena and shallow landslides affecting the outcropping calcareous rocks in the upper part of the basin, while, along the channel, the flow takes charge of the moraine loose material covering the toe of the slopes
In order to determine the rheological parameter values characterising the behaviour of a debris flow, it was realized, at first, a grain-size analysis was needed and later rheological ones
Summary
Debris flows are one of the most dangerous and destructive processes that concern mountain areas (Cavalli et al, 2005). The objective of the present study is to execute a simulation of the debris-flow event which occurred with a numerical code in order to determine if simulation results with rheological parameters obtained through laboratory analyses are comparable with results obtained with parameters calculated through back analyses. The results were compared among each other, and with the real event in order to understand the applicability range of data achieved by laboratory analyses through the instrument used All these simulations have been realized through the commercial software FLO-2D (2007 version). The material involved in the occurred debris flow is produced by erosional phenomena and shallow landslides affecting the outcropping calcareous rocks in the upper part of the basin, while, along the channel, the flow takes charge of the moraine loose material covering the toe of the slopes. During the alluvial event of 2003, the debris flow involved an estimated total volume of about 6000.00 m3
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