In the Swiss National Park, debris flows are a frequent
phenomenon and have repeatedly affected highways and hiking
structures. In this study, we first investigated the main characteristics and dimensions of current debris flows by field work and empirical parameterization schemes. Additionally, we evaluated a topography-based flow-trajectory geographic information system model (MSF) and a flow-routing model (FLO-2D) in terms of
debris flow-affected areas. Three generically different digital elevation models (DEM) with grid spacing of 25, 4, and 1 m were used in conjunction with the flow models. The evaluation of the DEM grid spacing shows that for both flow models the 25-m DEM can give an approximate estimation of the potential hazard zone.
Four- and one-meter DEMs mostly confine the simulated debris
flow to existing channels and are in accordance with observations of recent debris-flow events. The study shows that DEM quality and grid resolution are crucial for the resulting delineation of potentially affected areas and thus for hazard assessment and mapping.