How are fine sediments described in sediment sheet flow?

Abstract

Stony debris flow transits to sediment sheet flow when the river bed gradient becomes gentle. The sediment sheet flow consists of a water flow layer and a sediment moving layer. Fine sediments are expected to behave as a part of the fluid rather than a solid phase in the sediment moving layer. Further, it can be thought that a part of fine sediment can be suspended in the water flow layer. However, it was not possible to physically express whether the fine sediment behaves as a solid phase or a fluid phase in the numerical simulation model. Here we physically modeled fine sediment behavior in sediment sheet flow. We confirmed the applicability of the new model to describe the longitudinal deposited sediment gradient in flume experiments.