Subaqueous Barchans and Plane Beds from Deposition of Quartz Silt

Preprint of Capape, S., Martín-Vide, J., and Colombo, F. (2016). “Subaqueous Barchans and 1 Plane Beds from Deposition of Quartz Silt.” J. Hydraul. Eng., 10.1061/(ASCE)HY.19432 7900.0001212, 06016020 3 Subaqueous Barchans and Plane Beds from Deposition of Quartz Silt 4 S. Capape*, J.P. Martín-Vide, and F. Colombo 5 Abstract 6 The suspension flow of quartz silt (geometric mean grain size of 4.15 microns), in unfavourable 7 conditions for the deposition, originates the development of different bed morphologies. Particles 8 deposit over a plane, non-erodible surface and develop well-defined barchan ripples, barchanoids 9 and plane beds in flume experiments. Bed-load transport of quartz silt by bedform migration is 10 several orders of magnitude smaller than the suspended transport. The final bed morphology is 11 controlled by the suspended sediment concentration and the running time of the experiment. The 12 average dimensions of the bedforms after one-day experiments are 4.93 cm wide, 10.33 cm long 13 and 0.45 cm high. Cohesive plane beds appear after two and three-days experiments with very 14 high sediment concentration (≥ 22.5 kg/m). Viscous effects are deemed relevant for the formation 15 of the beds. DOI: 10.1061/(ASCE)HY.1943-7900.0001212. © 2016 American Society of Civil 16 Engineers. 17