Susceptibility and Triggers for Debris Flows: Emergence, Loading, Release and Entrainment

Abstract

Debris flows generally form when unconsolidated material becomes saturated and unstable, either on a hillslope or in a stream channel. The process is defined as a moving mass of loose mud, sand, soil, rock, water and air that travels down a slope under the influence of gravity. Flows can carry material ranging in size from clay to boulders, and may contain a large amount of woody debris. Volumes of material delivered by single events vary from less than 100 to more than 100,000m3. Generally three factors are necessary for a debris flow to develop: water, sufficient inclination, and abundant sediment supply.