Experiments on deposition behavior of fine sediment in a reservoir

The deposition behavior of fine sediment is an important phenomenon, and yet it is unclear to
engineers concerned about reservoir sedimentation. Laboratory experiments were conducted to produce both
quasi-homogeneous flow and a turbidity current region divided by a plunge section. Silica powder (a noncohesive
sediment) and kaolin (a cohesive sediment) were used as the suspended material. Because the effective gravitational
force is the primary driving force for velocity in turbidity currents, the velocity profile was closely
related to the concentration profile. The deposition rate of noncohesive coarser particles exponentially decays
along the flow path. Most of the coarser particles were deposited in the quasi-homogeneous flow region or
within a small distance downstream of the plunge section. The plunge did not carry those coarser particles
further downstream. Deposition in the region of the turbidity current was found mainly by cohesive particles.
Hydraulic sorting exists in the quasi-homogeneous flow region for noncohesive coarser particles, but becomes
less significant in the downstream portion with deposition rates becoming mildly decayed. For fine cohesive
particles, hydraulic sorting for the deposited gradation is not significant.