Assessment of debris flow deposition areas: empirical methods, laboratory tests and application to a case study

Debris and hyper-concentrated flows are among the most destructive of all water-related disasters and in the recent years have attracted more and more attention from the scientific and professional communities and concern from public awareness, due to the increasing frequency with which they occur and the death toll they claim. The study of debris flows can be subdivided into three main topics: the assessment of the magnitude of the phenomenon, the study of debris flow motion and the determination of the extension of the deposits. This last issue is of paramount importance from an engineering point of view, due to the fact that it determinates the areas that must be considered at risk, with all the consequences linked to the protection of population, and the predisposition of safety plans concerning different activities such as building construction. In this paper, a review of the most important empirical procedures of prediction of depositional areas is presented, with the aim to verify the applicability of the formulas to events different from those for which the methods were calibrated and then to try to unify them in order to originate a more reliable methodology. Laboratory tests were carried out to integrate the data available in the literature. The experimental data have been recorded with photogrammetry methods and 3D models of the deposits have been designed and validated. Then, the carried out procedure is applied to a small catchment in the North of Italy. The proposed empirical method will allow one to improve both mitigation measures and hazard mapping procedures. Keywords Debris flow, deposits on alluvial fan, empirical method, laboratory tests Language: en

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