Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 6 1 2006 10.5194/nhess-6-155-2006 http://www.nat-hazards-earth-syst-sci.net/6/155/2006/ http://www.nat-hazards-earth-syst-sci.net/6/155/2006/nhess-6-155-2006.html http://www.nat-hazards-earth-syst-sci.net/6/155/2006/nhess-6-155-2006.pdf 155 165 2006-02-27 Comparison of flow resistance relations for debris flows using a one-dimensional finite element simulation model D. Naef D. Rickenmann P. Rutschmann B. W McArdell WSL Swiss Federal Research Institute, Dept. of Natural Hazards, 8903 Birmensdorf, Switzerland BOKU University of Natural Resources and Life Sciences, Institute of Mountain Risk Engineering, 1190 Vienna, Austria University of Innsbruck, Institute of Hydraulic Engineering, 6020 Innsbruck, Austria now at: Emch+Berger AG, 3001 Bern, Switzerland This paper describes a one-dimensional finite element code for debris flows developed to model the flow within a steep channel and the stopping conditions on the fan. The code allows the systematic comparison of a wide variety of previously proposed one-phase flow resistance laws using the same finite element solution method. The one-dimensional depth-averaged equations of motion and the numerical model are explained. The model and implementation of the flow resistance relations was validated using published analytical results for the dam break case. Reasonable agreement for the front velocities and stopping location for a debris-flow event in the Kamikamihori torrent in Japan can be achieved with turbulent flow resistance relations including "stop" terms which allow the flow to come to rest on a gently sloping surface. While it is possible to match the overall bulk flow behavior using relatively simple flow resistance relations, they must be calibrated. A sensitivity analysis showed that the shape of the upstream input hydrograph does not much affect the flow conditions in the lower part of the flow path, whereas the event volume is much more important.