Flexural rigidity and shoot reconfiguration determine wake length behind saltmarsh vegetation patches

Marjoribanks, T.I., Lague, D., Hardy, R.J., Boothroyd, R.J. , Leroux, J., Mony, C. and Puijalon, S. (2019) Flexural rigidity and shoot reconfiguration determine wake length behind saltmarsh vegetation patches. Journal of Geophysical Research: Earth Surface, 124(8), pp. 2176-2196. (doi: 10.1029/2019jf005012)

Abstract

Vegetation patches play an important role in controlling sediment deposition in shallow aquatic environments such as coastal saltmarshes and fluvial systems. However, predicting deposition around vegetation patches is difficult due to the complexity of patch morphology and their dynamic interaction with the flow. Here we incorporate a biomechanical model, parameterized using field data, within a 3D computational fluid dynamics (CFD) model which allows prediction of individual shoot reconfiguration within patches due to flow forcing. The model predicts velocity attenuation and bed shear stresses within the wake of the patch which agree spatially with accretion patterns measured in the field using terrestrial LiDAR. The model is applied to sparse patches of Suaeda maritima, located in saltmarshes of coastal habitats, to explore the role of (I) shoot distribution, (II) patch geometry, (III) shoot flexural rigidity and (IV) bulk flow velocity in determining the length of the predicted wake region. We demonstrate that for Suaeda maritima, with intermediate rigidity, the vertical shear layer over the vegetation controls the length of the predicted wake region. Consequently, reconfiguration due to flexural rigidity strongly impacts on wake length, confounding the relationship between patch height and wake length. A simplified model for predicting wake length based on shoot reconfiguration is applied to the simulation data and shows good agreement. The results demonstrate that the observed wake characteristics can be well‐explained by intraspecific variability in flexural rigidity, thus demonstrating the importance of biomechanical traits in determining flow‐vegetation‐sediment interactions.

• Item Type: Articles
• Additional Information: TM and RJH acknowledge funding under NERC Grant NE/K003194/1 and DL and JL acknowledge project funding from CNRS/EC2CO/PNEC and PEPS terre-mer.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Boothroyd, Dr Richard
• Authors: Marjoribanks, T.I., Lague, D., Hardy, R.J., Boothroyd, R.J., Leroux, J., Mony, C., and Puijalon, S.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Journal of Geophysical Research: Earth Surface
• Publisher: American Geophysical Union
• ISSN: 2169-9011
• ISSN (Online): 2169-9011
• Published Online: 06 August 2019
• Copyright Holders: Copyright © 2019 American Geophysical Union
• First Published: First published in Journal of Geophysical Research: Earth Surface 124(8):2176-2196
• Publisher Policy: Reproduced in accordance with the publisher copyright policy
• Data DOI: 10.17028/rd.lboro.7588934