Plant effects on hydrodynamics and sedimentation at coastal wetland edges
Gillis, L.G.; Maza, M.; Argemi, M.; Balke, T.; Folkard, A.M.; Garcia-Maribona J.; Geng L.; Lanzoni, S.; Meire, D.; Paul, M.; Sgarabotto, A.; Suzuki, T.; Lara J.L. (2019). Plant effects on hydrodynamics and sedimentation at coastal wetland edges, in: Henry, P.-Y. et al. Trans-national Access in Hydralab+: Proceedings of the Joint User Meeting Bucharest, Romania, 22-23 May 2019. pp. [1-7]
In: Henry, P.-Y.; Breteler, M.K. (Ed.) (2019). Trans-national Access in Hydralab+: Proceedings of the Joint User Meeting Bucharest, Romania, 22-23 May 2019. [S.n.]: [s.l.]. , more
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Document type: Conference paper
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| Abstract |
Coastal wetlands such as mangrove forests and salt marshes form the final terrestrial frontier facing the open sea. Wetlands attenuate wave energy, decelerate currents and affect turbulence, which can have profound implications for the morphological development of coastal wetlands such as coastal vegetation retreat or progradation. Offshore hydrodynamic forcing and mechanical (rigidity, buoyancy) and spatial (density) vegetation traits determine these processes. Using DHI’s shallow water basin facility, we aimed to quantify how salt marsh and mangrove mimic vegetation attenuate wave and current energy, modify turbulent kinetic energy (TKE), and thus control sediment transport. These factors will determine wetland progradation rate or landward retreat. Combining densities of vegetation, mimic vegetation types (mangrove and salt marsh), waves and currents allows us to tease apart controlling factors of retreat and progradation in these environments. Sedimentation rates varied across mangrove and salt marsh vegetation, hydrodynamic conditions and densities. When only waves were deployed, both vegetation types showed accumulation of sediment, but for mangroves this was only at the patch front. The addition of currents did not change accumulation patterns for salt marshes but it did indicate erosion at the front of the mangrove mimic patch. Reducing mimic density caused erosion in both mimic patches, with salt marsh mimics characterised by erosion at the patch back whilst for mangroves erosion localised in the patch middle. The wave height decay observed along the two vegetation types relates to the accretion patterns observed within the meadow compared to the open channel. The erosion observed in both patches when their density was reduced is linked to an increase of TKE inside the meadow when it is sparser. Our results complement recent work by obtaining a better understanding of wave-current flow features at vegetation edges expanding our understanding of coastal wetland dynamics, and providing information used to increase coastal resilience and therefore protection. |
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