Hyper-concentrated flows: experimental investigation of effect of inflow parameters and sediment concentration on propagation process

Debris-flows runout estimations are of crucial importance to delineate the potentially hazardous areas and to make reliable assessment of the level of risk of urban areas. Especially in recent years, several researches have been conducted in order to define predicitive models. But, existing runout estimation methods need input parameters that can be difficult to estimate. Recent experimental researches have also allowed the assessment of the physics of the debris flows. But, the major part of the experimental studies analyze the basic kinematic conditions which determine the phenomenon evolution. Experimental program has been recently conducted at the Hydraulic laboratory of the Department of Civil, Environmental, Aerospatial and of Materials (DICAM) – University of Palermo (Italy). The experiments, carried out in a laboratory flume appositely constructed, were planned in order to evaluate both the effect of sediment concentration and the influence of the geometrical parameters (such as the slope and the geometrical characteristics of the confluences to the main channel) on the propagation phenomenon of the debris flow and its deposition. The laboratory flume reproduces the protection channel which is under construction in Giampilieri (Messina – Italy). The experimental apparatus includes a high-precision camera allowing the estimation of hyperconcentrated flow velocity by applying the VIA technique. Attention is particularly focused on flowing of sediment-water mixture for different geometrical characteristics (slope, angle,..) of the inflow channels and/or by introducing roughness elements on the bed. The propagation phenomenon is analyzed and discussed for different concentrations of sediments