ABSTRACT
Common knowledge points to conditions with u ∗ ≫ w s https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315623207/4fbc492d-6678-4a12-aaf6-5c2b8ea38e5f/content/eq169.tif"/> (with u ∗ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315623207/4fbc492d-6678-4a12-aaf6-5c2b8ea38e5f/content/eq170.tif"/> the shear velocity and ws the settling velocity) for a significant sediment suspension (Bagnold 1966). However, in tests with u ∗ ≫ w s https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315623207/4fbc492d-6678-4a12-aaf6-5c2b8ea38e5f/content/eq171.tif"/> multiple bed morphologies developed from the deposition of quartz silt (geometric mean size Dg = 4.15 μm) over a plane, non-erodible surface in turbulent conditions and constant flow discharge for different initial sediment concentrations. Mean grain size of the deposited particles is coarser than the initial silt in suspension. Final bed morphology is controlled by the suspended sediment concentration and the running time of the experiment. Surrogate measures of suspended sediment concentration from backscatter strength from an ADV display incorrect results because suspended sediment concentration is too high (>~1 kg/m3), there are passing bedforms, and grain size distribution varies with time. Viscous effects are deemed relevant for the formation of the quartz silt beds.
