Preprints
https://doi.org/10.5194/esurf-2021-13
https://doi.org/10.5194/esurf-2021-13

  02 Mar 2021

02 Mar 2021

Review status: this preprint is currently under review for the journal ESurf.

Sediment shell-content diminishes current-driven sand ripple development and migration

Chiu H. Cheng1, Jaco C. de Smit1,2, Greg S. Fivash1, Suzanne J. M. H. Hulscher3, Bas W. Borsje3, and Karline Soetaert1 Chiu H. Cheng et al.
  • 1NIOZ Royal Netherlands Institute for Sea Research, Department of Estuarine and Delta Systems (EDS), 4400 AC Yerseke, The Netherlands
  • 2Faculty of Geosciences, Department of Physical Geography, Utrecht University, 3584 CB Utrecht, The Netherlands
  • 3Water Engineering and Management, University of Twente, 7500 AE Enschede, The Netherlands

Abstract. Shells and shell fragments are biogenic structures that are widespread throughout natural sandy shelf seas and whose presence can affect the bed roughness and erodibility of the seabed. An important and direct consequence is the effect on the formation and movement of small bedforms such as sand ripples. We experimentally measured ripple formation and migration of a mixture of natural sand with increasing volumes of shell material in a racetrack flume. Our experiments reveal the impacts of shells on ripple development in sandy sediment, providing information that was previously lacking. Shells expedite the onset of sediment transport while simultaneously reducing ripple dimensions and slowing down their migration rates. Moreover, increasing shell content enhances near-bed flow velocity due to the reduction of bed friction that is partly caused by a decrease in average ripple size and occurrence. This, in essence, limits the rate and magnitude of bedload transport. Given the large influence of shell content on sediment dynamics on the one hand, and the high shell concentrations found naturally in the sediments of shallow seas on the other hand, a significant control from shells on the morphodynamics of sandy marine habitats is expected.

Chiu H. Cheng et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-13', Anonymous Referee #1, 29 Mar 2021
  • RC2: 'Comment on esurf-2021-13', Jaco H Baas, 05 Apr 2021

Chiu H. Cheng et al.

Chiu H. Cheng et al.

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Short summary
Shells are biogenic particles that are widespread throughout natural sandy environments and can affect the bed roughness and seabed erodibility. As studies are presently lacking, we experimentally measured ripple formation and migration using natural sand with increasing volumes of shell material under unidirectional flow in a racetrack flume. We show that shells expedite the onset of sediment transport, reduce ripple dimensions and slow their migration rate.