TY - JOUR

T1 - Particle size segregation of turbidity current deposits in vegetated canopies

AU - Soler, Marianna

AU - Colomer, Jordi

AU - Folkard, Andrew

AU - Serra, Teresa

N1 - This is the author’s version of a work that was accepted for publication in Science of the Total Environment. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Science of the Total Environment, 703, 2020 DOI: 10.1016/j.scitotenv.2019.134784

PY - 2020/2/10

Y1 - 2020/2/10

N2 - Interactions between ecology, hydrodynamics and sediments play central roles in the evolution of coastal and freshwater ecosystems. We set out to characterise interactions of a specific hydrodynamic phenomenon – turbidity currents – with vegetation and sediment dynamics. We measured hydrodynamics and sediment deposition rates when turbidity currents flowed into plant canopies in a lock-exchange flume experiment, using simulated vegetation and three real plant species, and varying the turbidity current’s initial sediment concentration. The natural sediment used had an essentially bimodal size distribution, with coarse (6.2-104 μm) and fine (2.2-6.2 μm) fractions. In all cases, on entering the vegetation canopy, the turbidity current was initially inertially-dominated, but subsequently became drag-dominated. In the inertial regime, there was no size segregation in the deposited material. In the drag-dominated regime, the deposited material became increasingly dominated by fine sediment, at a rate dependent on the vegetation type. The transition between these two regimes occurred at a distance equivalent to 5.1 to 7.6 times the total water depth downstream of the lock gate. The size segregation of deposited sediment is posited to have consequences for substrate evolution, which in turn may affect vegetation growth. Thus, our findings point to a non-linear feedback mechanism between the spatial heterogeneity of vegetation canopies and that of the substrate they help to engineer.

AB - Interactions between ecology, hydrodynamics and sediments play central roles in the evolution of coastal and freshwater ecosystems. We set out to characterise interactions of a specific hydrodynamic phenomenon – turbidity currents – with vegetation and sediment dynamics. We measured hydrodynamics and sediment deposition rates when turbidity currents flowed into plant canopies in a lock-exchange flume experiment, using simulated vegetation and three real plant species, and varying the turbidity current’s initial sediment concentration. The natural sediment used had an essentially bimodal size distribution, with coarse (6.2-104 μm) and fine (2.2-6.2 μm) fractions. In all cases, on entering the vegetation canopy, the turbidity current was initially inertially-dominated, but subsequently became drag-dominated. In the inertial regime, there was no size segregation in the deposited material. In the drag-dominated regime, the deposited material became increasingly dominated by fine sediment, at a rate dependent on the vegetation type. The transition between these two regimes occurred at a distance equivalent to 5.1 to 7.6 times the total water depth downstream of the lock gate. The size segregation of deposited sediment is posited to have consequences for substrate evolution, which in turn may affect vegetation growth. Thus, our findings point to a non-linear feedback mechanism between the spatial heterogeneity of vegetation canopies and that of the substrate they help to engineer.

KW - Turbidity current

KW - Aquatic vegetation

KW - sediment deposition

KW - gravity current

U2 - 10.1016/j.scitotenv.2019.134784

DO - 10.1016/j.scitotenv.2019.134784

M3 - Journal article

VL - 703

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 134784

ER -