Routing debris flows

As population encroaches into areas susceptible to debris flows, it becomes increasingly important to provide information delineating these hazards. T his paper presents a simple, yet versatile technique to model the behavior of a debris flow as it progresses down a stream channel. The simplicity der ives from modeling the center of mass of the flow using one-dimensional for ce-equilibrium concepts. The resulting quadratic equation is amenable to em bedding within a Geographic Information System structure. The versatility d erives from its ability to: 1. Estimate over-bank now. 2. Estimate mass gain and loss during flow. 3. Account for changes in debris flow viscosity and mass density. 4. Account for the effects of stream channel geometry. 5. Estimate debris flow travel times. The technique is demonstrated by simulating a suite of debris flows using N ewton Creek, Oregon, as a representative stream channel. Simulations show t hat the technique is able to approximate the inundation areas, bulking fact ors and travel times of observed debris flows.