Sediment Entrainment and Deposition

Many debris flows have significant amounts of entrainment, resulting in a substantially larger final volume than their initial volume and more complicated mechanics and characteristics of the flow. This chapter reviews some historical cases with substantial entrainment and erosion mechanisms that have been commonly considered in studying debris flow entrainment. The formation of a debris flow along with dominant factors affecting flow characteristics are comprehensively reviewed, and the erosion process is described. The instruments used to monitor erosion depth/rate and factors affecting the rate of erosion are summarized. It is commonly agreed that key factors affecting debris flow entrainment are topography, initial volume, solid concentration and particle size distribution, which are also discussed in this chapter. The entrainment and deposition models are classified based on the erosion mechanisms, and limitations and advantages of these entrainment models are discussed and summarized. In addition, physical modelling equipment is tabulated, and various numerical entrainment runout models are compared and discussed. This chapter provides a review of debris flow entrainment studies in the last two decades and may be of help to researchers studying debris flow entrainment in the future.