To predict the run out distance and extent of the hazard area of rainfall-induced debris flows

we proposed a depth-averaged two-dimensional numerical model

in which the debris and water mixture is assumed to be a uniform continuous

incompressible

unsteady Newtonian turbulence fluid. As raster grid networks of digital elevation model in GIS can be used as the finite difference mesh

the continuity and momentum equations are solved numerically using the finite difference method. All the input data and output are processed in GIS. The model is applied to simulate the rainfall-induced real debris flow of July 20

2003

in Minamata City of southern Kyushu

Japan. The simulation reproduces the propagation of the real debris flow; and the results are in good agreement with the field investigation. The two-dimensional numerical simulation using GIS can be used to estimate the potentially inundated areas

the potentially dangerous homes and roads for hazard and risk analysis.