A Convolution Method to Assess Subgrid‐Scale Interactions Between Flow and Patchy Vegetation in Biogeomorphic Models

Gourgue, Olivier; Belzen, Jim van; Schwarz, Christian; Bouma, Tjeerd J.; Koppel, Johan van de; Temmerman, Stijn

doi:10.1029/2020ms002116

Cited by 14 publications

(26 citation statements)

References 116 publications

(238 reference statements)

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“…The first approach increases the actual bed shear stress due to surface roughness (τ b ) with a vegetation roughness component (τ v ) (c.f. Gourgue et al, 2020). The second approach reduces the flow momentum with a drag term based on vegetation properties such as density, diameter, height and drag coefficient (c.f.…”

Section: Hydrodynamic Processesmentioning

confidence: 99%

Nature-Based Engineering: A Review on Reducing Coastal Flood Risk With Mangroves

et al. 2021

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Integration of mangroves in projects to reduce coastal flood risk is increasingly being recognised as a sustainable and cost-effective alternative. In addition to the construction of conventional hard flood protection infrastructure, mangroves not only contribute to attenuating flood events (functionality), they also recover in, and adapt to, a changing climate (persistence). The implementation of mangroves in flood risk reduction, however, remains complex. This is because the innate functionality and persistence of mangroves depend on a range of environmental conditions. Importantly, mangroves may collapse when environmental impacts or climatic changes exceed key system thresholds, bringing uncertainty into a situation where failure could endanger lives and livelihoods. The uncertainties in mangrove functionality and persistence can be dealt with by (1) improving insights in how ecological and physical processes affect mangrove functionality and persistence across scales, (2) advancing tools to accurately assess and predict mangrove functionality and persistence, and (3) adopting an adaptive management approach combined with appropriate engineering interventions to enhance mangrove functionality and persistence. Here, we review existing evidence, monitoring techniques and modelling approaches from the viewpoint of mangrove functionality and persistence. Inspired by existing guidelines for Nature-based Solutions (NbS) to reduce flood risk, we provide an operationalization for this new approach. In addition, we identify where further research efforts are required for the practical application of mangroves in coastal flood risk management. Key aspects in the variability and uncertainty of the functionality and persistence of mangroves are their failure and recovery mechanisms, which are greatly site- and storm-specific. We propose five characteristic damage regimes that result in increasing reductions of mangrove functionality as well as post-storm recovery periods. Further research on the quantification of these regimes and their thresholds is required for the successful integration of mangroves in coastal flood risk management. Ultimately, the key challenge is the development of adaptive management strategies to optimise long-term mangrove functionality and persistence, or their resilience. Such adaptive strategies should be informed by continued mangrove functionality and persistence assessments, based on continued monitoring and modelling of key mangrove thresholds, and supported through well-established guidelines.

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Section: Hydrodynamic Processesmentioning

confidence: 99%

Nature-Based Engineering: A Review on Reducing Coastal Flood Risk With Mangroves

et al. 2021

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“…This can create potential hotspots for biodiversity (Elsey-Quirk et al, 2019) and determine changes in vegetation distribution according to the ability of individual species to tolerate such stresses, which in turn depends on the specific vegetation traits (Leonard and Croft, 2006;Van Wesenbeeck et al, 2008;Schoutens et al, 2020;Schulte Ostermann et al, 2021). On the one hand, some of the abiotic factors, especially the hydrodynamic ones, could be included rather easily in the model, for example by weighting the habitat quality based on stresses calculated from hydrodynamic models or, alternatively, as a function of the distance of each site from marsh edges exposed to the action of waves and currents (see for example Gourgue et al, 2021a;Kalra et al, 2021). On the other hand, however, most of the biotic factors affecting vegetation dynamics are difficult to conceptualize, as they depend on the community ecology of marsh fauna (Gaskins et al, 2020;Burdick et al, 2021;Pennings and He, 2021).…”

Section: Model Limitations and Future Developmentsmentioning

confidence: 99%

“…Our model can be coupled with virtually any hydromorphodynamic model to simulate the intertwined evolution of marsh halophytes and topographic gradients under varying rates of relative sea-level rise and sediment supply. If the models employ different types of grids or spatial resolutions, the coupling can also be performed using subgrid schemes together with appropriate multiscale coupling techniques (e.g., Gourgue et al, 2021a;Gourgue et al, 2021b;Kalra et al, 2021). The evolution of marsh topography at each site will be obtained by a combined geomorphological balance between erosion and sedimentation, computed by the morphodynamic model, and organic production by halophytic vegetation, calculated by the vegetation model.…”

Section: Model Limitations and Future Developmentsmentioning

confidence: 99%

A Minimalist Model of Salt-Marsh Vegetation Dynamics Driven by Species Competition and Dispersal

et al. 2022

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We present a new bidimensional, spatially-explicit ecological model describing the dynamics of halophytic vegetation in tidal saline wetlands. Existing vegetation models employ relatively simple deterministic or stochastic mechanisms, and are driven by local environmental conditions. In the proposed model, in contrast, vegetation dynamics depend not only on the marsh local habitat, but also on spatially-explicit mechanisms of dispersal and competition among multiple interacting species. The role of habitat quality, here determined by the local elevation relative to the mean sea level as a proxy for environmental conditions, is mathematically modeled by a logistic function that represents the fundamental (theoretical) niche of each halophytic species. Hence, the model does not artificially impose any constraints to the ability of a species to colonize elevated areas where it is usually not observed: such limitations naturally arise through competition with fitter species across marsh topographic gradients. We qualitatively test our model against field data based on a suitable assemblage of focus species, and perform a sensitivity analysis aimed at determining how dynamic equilibria in vegetation distributions are affected by changes in model input parameters. Results indicate that the model is robust and can predict realistic vegetation distributions and species-richness patterns. More importantly, the model is also able to effectively reproduce the outcomes of classical ecological experiments, wherein a species is transplanted to an area outside its realized niche. A direct comparison shows that previous models not accounting for dispersal and interspecific competitions are unable to reproduce such dynamics. Our model can be easily integrated into virtually any existing morphodynamic model, thereby strengthening our ability to simulate the coupled biotic and abiotic evolution of salt marshes under changing climate forcings.

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“…There is an urgent need for further developing models of biophysical feedback mechanisms, enabling the projection of possible future morphologic developments within MR schemes. Recent advancements in this regard are presented by Gourgue et al (2020), who developed a computationally efficient model to account for the impact of sub-grid-scale vegetation patches on the relationship between water flow and sediment dynamics. Such knowledge is crucial for the flood defence functionality of saltmarshes, as it defines long-term trends regarding elevation, vegetation type/coverage and features such as marsh cliffs and channels (Reed et al 2018).…”

Section: Considerations On the Effects Of Morphologic Site Evolution On Hwl Attenuation Ratesmentioning

confidence: 99%

Can Managed Realignment Buffer Extreme Surges? The Relationship Between Marsh Width, Vegetation Cover and Surge Attenuation

Kiesel

MacPherson

Schuerch

et al. 2021

Estuaries and Coasts

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Managed realignment (MR) involves the landward relocation of sea defences to foster the (re)creation of coastal wetlands and achieve nature-based coastal protection. The wider application of MR is impeded by knowledge gaps related to lacking data on its effectiveness under extreme surges and the role of changes in vegetation cover, for example due to sea-level rise. We employ a calibrated and validated hydrodynamic model to explore relationships between surge attenuation, MR width(/area) and vegetation cover for the MR site of Freiston Shore, UK. We model a range of extreme water levels for four scenarios of variable MR width. We further assess the effects of reduced vegetation cover for the actual MR site and for the scenario of the site with the largest width. We show that surges are amplified for all but the largest two site scenarios, suggesting that increasing MR width results in higher attenuation rates. Substantial surge attenuation (up to 18 cm km−1) is only achieved for the largest site. The greatest contribution to the attenuation in the largest site scenario may come from water being reflected from the breached dike. While vegetation cover has no statistically significant effect on surge attenuations in the original MR site, higher coverage leads to higher attenuation rates in the largest site scenario. We conclude that at the open coast, only large MR sites (> 1148 m width) can attenuate surges with return periods > 10 years, while increased vegetation cover and larger MR widths enable the attenuation of even higher surges.

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A Convolution Method to Assess Subgrid‐Scale Interactions Between Flow and Patchy Vegetation in Biogeomorphic Models

Cited by 14 publications

References 116 publications

Nature-Based Engineering: A Review on Reducing Coastal Flood Risk With Mangroves

Nature-Based Engineering: A Review on Reducing Coastal Flood Risk With Mangroves

A Minimalist Model of Salt-Marsh Vegetation Dynamics Driven by Species Competition and Dispersal

Can Managed Realignment Buffer Extreme Surges? The Relationship Between Marsh Width, Vegetation Cover and Surge Attenuation

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