GIS-BASED CELL MODEL FOR SIMULATING DEBRIS FLOW ROUTING AND DEPOSITION PHASES ON A FAN

A GIS-based cell model is proposed for the simulation of the routing and deposition phases of debris flow on a fan. Flow pattern is discretized by square cells, 2m size, which coincide with the DEM cells and the mixture is assumed a monophasic continuum. Flow exchange between adjacent cells is ruled by uniform flow or broad-crested weir laws and by continuity equation. Flow occurs from cells with higher surface to those with lower surface and is simulated by uniform flow law if the elevation of the formers is higher than the latter and by broad-crested weir law otherwise. Erosion and deposition are simulated using the empirical law of Egashira, adjusted for monophasic continuum. The cell model is used to simulate debris flow occurred on Rio Lazer (Dolomites, Eastern Italian Alps) the 4th of November 1966. The same event was also simulated using Flo-2D model for a comparison with a widely used model for debris flow simulation. Results of the two simulations were compared with extension of deposition area and the map of measured depths of deposited sediments. Both the model simulate quite well the extent of deposition area, whereas the deposited debris depths are better simulated by the cell model.