Application and validation of a three-dimensional hydrodynamic model of a macrotidal salt marsh

Ashall, Logan M.; Mulligan, Ryan P.; Proosdij, Danika van; Poirier, Emma

doi:10.1016/j.coastaleng.2016.04.005

Cited by 33 publications

(25 citation statements)

References 35 publications

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“…Similar across‐marsh flows are also found by Ashall et al. () in the modeling of a macro‐tidal marsh without considering vegetation effects. At the draining‐off period, when vegetaion is included (left‐hand panel in Figure ), the flows on the platforms have very small velocities and are blocked by the levees surrounding the channels.…”

Section: Model Resultssupporting

confidence: 85%

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Subgrid modeling of salt marsh hydrodynamics with effects of vegetation and vegetation zonation

Liang

et al. 2017

Earth Surf Processes Landf

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Vegetation plays a critical role in modifying inundation and flow patterns in salt marshes. In this study, the effects of vegetation are derived and implemented in a high-resolution, subgrid model recently developed for simulating salt marsh hydrodynamics. Vegetation-induced drag forces are taken into account as momentum sink terms. The model is then applied to simulate the flooding and draining processes in a meso-tidal salt marsh, both with and without vegetation effects. Marsh inundation and flow patterns are significantly changed with the presence of vegetation. A smaller area of inundation occurs when vegetation is considered. Tides propagate both on the platform and through the channels when vegetation is absent, whereas flows concentrate mainly in channels when vegetation is present. Local inundation on vegetated platforms is caused mainly by water flux spilled from nearby channels, with a flow direction perpendicular to the channel edges, whereas inundation on bare platforms has contributions from both local spilled-over water flux and remote advection from adjacent platforms. The flooding characteristics predicted by the model showed a significant difference between higher marsh and lower marsh, which is consistent with the wetlands classification by the National Wetlands Inventory (NWI). The flooding characteristics and spatial distribution of hydroperiod are also highly correlated with the vegetation zonation patterns observed in Google Earth imagery. Regarding the strong interaction between flow, vegetation and geomorphology, the conclusion highlights the importance of including vegetation in the modeling of salt marsh dynamics.

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Section: Model Resultssupporting

confidence: 85%

“…In the presence of vegetation canopies, the flow routing patterns can be significantly modified (Ashall et al. ; Temmerman et al. ).…”

Section: Model Resultsmentioning

confidence: 99%

Subgrid modeling of salt marsh hydrodynamics with effects of vegetation and vegetation zonation

Liang

et al. 2017

Earth Surf Processes Landf

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“…Complete removal of vegetation increases flow velocities on the marsh platform, which has been shown in a field experiment (Temmerman et al ) and in a number of modeling studies (Temmerman et al ; Ashall et al ; Wu et al ). The increase in flow velocity has been attributed to reduced friction and would imply lower sedimentation rates or even erosion after marsh die‐off (Silliman et al ; Sheehan and Ellison ; Coleman and Kirwan ).…”

mentioning

confidence: 67%

How progressive vegetation die‐off in a tidal marsh would affect flow and sedimentation patterns: A field demonstration

Schepers

Braeckel

Bouma

et al. 2019

Limnology & Oceanography

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Coastal marshes provide valuable ecosystem functions, but some are facing increasing risks of vegetation loss due to sea level rise and other stressors. A key question is how tidal flow and sedimentation patterns are affected by the spatiotemporal patterns of vegetation loss, as sediment accretion with sea level rise largely affects the potential for marsh recovery. Here, we performed a field study in a macrotidal reed marsh and simulated typical spatiotemporal patterns of vegetation loss by consecutive mowing. For each mowing pattern, the spatial patterns of flow velocities and sedimentation rates were recorded. Our results indicate that initial vegetation loss in inner marsh portions, with an intact vegetation belt alongside channel edges, has limited effect on tidal flows over the marsh. However, subsequent creation of unvegetated corridors connecting the bare inner marsh and the channels increases flow velocities in these corridors but not in remaining vegetation patches. Finally, when all vegetation is removed, sheet flow occurs over the whole marsh instead of concentrated channel flow. Effects on spatial sedimentation patterns are complex and not significant on all measuring locations. Nevertheless, our study indicates that complete vegetation removal results in redistributed sedimentation patterns, with a general tendency of locally reduced sedimentation rates close (< 15 m) to channels and increased sediment supply to inner marshes 15–50 m from channels. Our results highlight that feedbacks between spatial patterns of vegetation loss, tidal sediment transport, and deposition are key to understanding and mitigating risks of marsh loss in face of sea level rise.

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“…Nonetheless, aspects of the dynamics here are comparable to those observed in other mangrove and salt marsh systems. In particular, Temmerman et al (2005) and Ashall et al (2016) report field observations and numerical modelling results of flows in meso-and macro-tidal salt marsh systems with flooding and draining occurring in a direction perpendicular to the vegetation line.…”

Section: Discussion Of Dynamics and Comparison With Previous Workmentioning

confidence: 99%

“…Delft3D-FLOW is a process-based hydrodynamic solver for the unsteady nonlinear shallow-water equations that has been used in a number of studies of vegetation effects on flow characteristics (e.g. Horstman et al, 2015;Ashall et al, 2016). In the present study, we use Delft3D-FLOW in pure hydrodynamic, 2D depth-averaged mode.…”

Section: Model Set Upmentioning

confidence: 99%

Spatially varying drag within a wave-exposed mangrove forest and on the adjacent tidal flat

Mullarney

Henderson

Reyns

et al. 2017

Continental Shelf Research

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Mangroves have been shown to protect shorelines against damage from the combined hydrodynamic forces of waves and tides, owing to the presence of roots (pneumatophores) and tree trunks that enhance vegetative drag. However, field measurements within these environments are limited. We present field observations of flows from the seaward coast of Cù Lao Dung Island (Sóc Trȃng Province) in the Mekong Delta, Vietnam. Measurements were made in two different seasons along a transect that crosses from mudflats to mangrove forest.

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Application and validation of a three-dimensional hydrodynamic model of a macrotidal salt marsh

Cited by 33 publications

References 35 publications

Subgrid modeling of salt marsh hydrodynamics with effects of vegetation and vegetation zonation

Subgrid modeling of salt marsh hydrodynamics with effects of vegetation and vegetation zonation

How progressive vegetation die‐off in a tidal marsh would affect flow and sedimentation patterns: A field demonstration

Spatially varying drag within a wave-exposed mangrove forest and on the adjacent tidal flat

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