An advanced methodology for debris flow analysis in the context of landslide hazard zoning

Landslide susceptibility zoning is becoming an important topic in scientific literature, especially in relation to land-use planning and management. The methods employed to derive landslide maps for zoning purposes are generally divided into three classes: heuristic or basic, statistical or intermediate and deterministic or advanced. Based on the method used, the scale of analysis and the zoning purpose, three zoning levels can be obtained i.e. preliminary, intermediate and advanced. For instance, when basic methods on a small scale are used, only a preliminary zoning level can be obtained while the use of intermediate and advanced methods, on a medium and large scale respectively, can allow us to achieve intermediate or advanced levels of zoning. All that considered, and with reference to a particular type of landslide called debris flow, a three-step deterministic method has been proposed. This method is based on a combination of two advanced models able to both identify the most relevant predisposing factors of debris flows in weathered gneiss and pursue an advanced level of susceptibility zoning on a large scale. The methodology, applied to a debris flow event which occurred in the province of Reggio Calabria, showed that the results obtained when combining these models are coherent with the prior-analysis of the real event. This is the starting point for a susceptibility analysis of debris flow over a large area.