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 com-munities 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 protec-tion 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 depo-sitional 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.
Debris flow, deposits on alluvial fan, empirical method, laboratory tests
 Lorenzini G., Brebbia C. & Emmanouloudis D. (eds.), Monitoring, simulation, preven-tion and remediation of dense and debris flows, WIT Press: Southampton, UK, 2006. doi: http://dx.doi.org/10.2495/DEB06
 Einstein, H., Special lecture: “Landslide risk assessment procedure”. Int. Symposium on Landslides. Landslide, Vol. 2, ed. C. Bonnard, pp. 1075–1090, 1988.
 Schultz, B., Flood management under rapid urbanization and industrialization in flood-prone areas: a need for serious consideration. Irrigation and Drainage, 55(Suppl. 1), pp. 3–8, 2006. doi: http://dx.doi.org/10.1002/ird.237
 Iverson, R., The debris-flow rheology myth. Debris-flow hazards mitigation: Mechan-ics, prediction, and assessment, Vol 1, eds. D. Rickenmann & C. Chen, Millpress: Rotterdam, pp. 303–314, 2003.
 Mambretti, S., Larcan, E. & De Wrachien, D., Theoretical and experimental analysis of debris flow: Rheology and two-phase modelling. Irrigation and drainage, 57(5), pp. 555–570, 2008. doi: http://dx.doi.org/10.1002/ird.383
 Mambretti, S., Larcan, E. & De Wrachien, D., 1D modelling of dam-break surges with floating debris. Biosystems Engineering, 100(2), pp. 297–308, 2008. doi: http://dx.doi. org/10.1016/j.biosystemseng.2008.02.011
 Liu, X., Size of debris flow deposition: Model experiment approach. Environmental Geology, 28(2), pp.70–77, 1996. doi: http://dx.doi.org/10.1007/s002540050079
 Yu, F., Chen, C., Chen, T. Hung, F. & Lin, S., A GIS process for delimitating areas poten-tially endangered by debris flow. Natural Hazards, 37, pp.169–189, 2006. doi: http://dx.doi. org/10.1007/s11069-005-4666-8
 Berti, M. & Simoni, A., Prediction of debris flow inundation areas using empirical mobility relationships. Geomorphology, 90, pp. 144–161, 2007. doi: http://dx.doi.org/10.1016/ j.geomorph.2007.01.014
 Rickenmann, D., Empirical relationships for debris flows. Natural Hazards, 19, pp. 47–77, 1999. doi: http://dx.doi.org/10.1023/A:1008064220727
 Iverson, R. & Schilling, S., Automated, reproducible delineation of zones at risk from inundation by large volcanic debris flows. Proceedings of first international conference on debris-flow hazards mitigation: Mechanics, prediction and assessment, ASCE: San Francisco, August 7–9, ,pp. 176–186, 1997.
 Prochaska, A., Santi, P., Higgins, J. & Cannon, S., Debris-flow run-out predictions based on the average channel slope (ACS). Engineering Geology, 98, pp. 29–40, 2008. doi: http://dx.doi.org/10.1016/j.enggeo.2008.01.011
 Iverson, R., The debris-flow rheology myth. Debris-flow hazards mitigation: Mechan-ics, prediction, and assessment, Vol. 1, eds. D. Rickenmann, & C. Chen, Millpress: Rotterdam, pp. 303–314, 2003.
 Corominas, J., The angle of reach as a mobility index for small and large landslide. Canadian Geotechnical Journal, 33, pp. 260–271, 1996. doi: http://dx.doi.org/10.1139/ t96-005
 Toyos, G., OramasDorta, D., Oppenheimer, C., Pareschi. M., Sulpizio, R. & Zanchetta, G. GIS-assisted modelling for debris flow hazard assessment based on the event of May 1998 in the area of Sarno, southern Italy: Part I: Maximum run-out. Earth Surface Processes and Landforms, 32, pp. 1491–1502, 2006. doi: http://dx.doi.org/10.1002/ esp.1472
 Mambretti, S. Valutazione della magnitudo di colate detritiche in funzione del tempo di ritorno nel Bacino di Val Gola (BG). GEAM, 1, pp. 15–24, 2007 (in Italian).
 De Wrachien, D. & Mambretti, S., Assessment of debris flow magnitude in small catchments of the Lombardy Alps: the Val Gola case study. Agricultural Sciences, 2(1), pp. 9–15, 2011. doi: http://dx.doi.org/10.4236/as.2011.21002
 Iverson, R.M., The physics of debris flows. Reviews Geophysics, 35(3), 245–296, 1997. doi: http://dx.doi.org/10.1029/97RG00426
 Ghilardi, F., Ghilardi, S. & Mambretti, S., Studio di dettaglio della conoide della Val Gola in comune di Costa Volpino. Technical Report, 2006 (in Italian).
 Takahashi, T., Debris Flow. International Association for Hydraulic Research: Balkema, Rotterderdam.