STUDY ON THE DEPOSITION OF DEBRIS FLOWS (3)-Erosion of Debris Fan

Many disasters have happened due to occurrence of so-called sediment flow, which is in manytimes originated from erosion of the debris flow deposit upstream. To understand the phenomena ofsediment flows, the author hydraulically defines the sediment flow and studies the mechanics of it.He proposes the formulae of sediment discharge, resistance to flow, and sediment concentrationsuitable for the sediment flow. Application of these formulae for erosion of a debris cone and re-deposit as an alluvial fan necessitates a simplified method to analyse the process. The author givesthe method and calculates the initial process successfully. The process of armour coating and thecharacteristics of rhythmic spacing of pools and riffles are also investigated.