The effect of long‐term aerial exposure on intertidal mudflat erodibility

Nguyen, Hieu M.; Bryan, Karin R.; Pilditch, Conrad A.

doi:10.1002/esp.4990

Cited by 10 publications

(9 citation statements)

References 69 publications

(141 reference statements)

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“…M indicates how quickly erosion rates increase when the critical bed shear stress is exceeded. Both (τ e ) and M can be measured with the EROMES device (Stokes and Harris, 2015;Nguyen et al, 2019Nguyen et al, , 2020. By gradually increasing the rotational speed of a propeller in the EROMES tube, the flow velocity and exerted bed shear stress at the surface of the sediment sample in the tube follow.…”

Section: Morphology and Sediment Transport 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: Morphology and Sediment Transport Processesmentioning

confidence: 99%

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

et al. 2021

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“…However, the type of models as presented here are also sensitive to the implementation of

τ_{cr}

. This study imposes a fixed gradient of

τ_{cr}

based on mean aerial exposure duration of the bed following Nguyen et al (2020) and calibrated with measured SSC values in the field. The model accurately simulates the long‐term profile development with realistic accretion rates.…”

Section: Discussionmentioning

confidence: 99%

“…In Equation (), τ cr,bare was determined following a model calibration (Section 2.4). For τ cr,drying , z was the bed level elevation relative to mean sea level (m + msl) and coefficients c 1 (0.106 N/m 3 ) and c 2 (3.898) were determined from the study of Nguyen et al (2020) in the Firth, in combination with the mean exposure duration of the intertidal area based on the Tararu tidal gauge water levels from 2017 (Figure 4; Supporting Information S1). For

τ_{italiccr, italicbiomass}

, B was the total mangrove biomass determined by the total mangrove biomass of all trees in a grid cell divided by the surface area of that particular grid cell and B max was the maximum mangrove biomass present in the forest (=202 kg/m 2 ).…”

Section: Methodsmentioning

confidence: 99%

Mangrove forest drag and bed stabilisation effects on intertidal flat morphology

Gijsman,

Horstman,

Swales

et al. 2023

Earth Surf Processes Landf

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Mangrove trees influence their physical environment by exerting drag on tidal flows and waves while also stabilising the sediment bed of intertidal flats. These processes influence sediment accretion, the mangrove habitat and their resilience to sea level rise. However, little is known about the magnitude and spatial extent of the effects of mangrove forests on sediment transport and the morphology of the intertidal flat. We use manipulated simulations with an extended process‐based numerical model, to study the influence of mangrove forests on intertidal flat morphology on a yearly timescale. The model includes the influence of mangrove trees on tidal flows, waves and sediment dynamics. The model is calibrated and validated with a comprehensive set of measurement data including hydrodynamics, sediment transport and morphological processes from an expanding mangrove forest in the sediment‐rich Firth of Thames estuary in Aotearoa New Zealand.Sediment accretion on the upper intertidal flat is predominantly influenced by the characteristic morphology of the established mangrove forest, with increased bed stability at higher mudflat elevations related to prolonged aerial exposure and drying of the bed. Our results show that, in comparison to the situation without mangroves, sediment accretion increases in the most seaward fringe area of the forest. The unvegetated intertidal flat fronting the mangrove forest captures less sediment compared to the situation without mangroves. The mangrove forest drag triggers the development of a steeper, convex‐up‐shaped, upper intertidal flat profile, especially during periods with higher water levels and waves. These effects are expected to influence the development and storm‐recovery of natural and restored mangrove forests and may contribute to the resilience and persistence of mangrove‐vegetated intertidal flats for coastal flood risk reduction.

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“…For example, heavy rainfall at low tide can destabilize sediments and increase sediment erodibility, making sediment beds more susceptible to erosion (Pilditch et al 2008). Long-term aerial exposure may result in intertidal-flat sediments becoming more consolidated and hence more stable, further affecting their resistance to erosion-the longer the aerial exposure, the more resistant the sediments are to erosion (Nguyen et al 2020). A neap tide was involved in this study (Fig.…”

Section: Discussionmentioning

confidence: 99%

Effect of typhoon‐induced intertidal‐flat erosion on dominant macrobenthic species (Meretrix meretrix)

Shi

Yang

Temmerman

et al. 2021

Limnology & Oceanography

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Benthic animal populations inhabiting intertidal flats provide important ecosystem functions and services that may be disrupted by physical disturbances such as tropical cyclones, which are predicted to increase in frequency and intensity under future climate change. However, the spatial reach at which tropical cyclones impact macrobenthos populations in intertidal flats remains poorly understood. We examined whether a typhoon with a center that remained more than 1400 km away from the study site could trigger severe erosion of intertidal flats and adversely affect macrobenthos populations. We undertook simultaneous measurements of hydrodynamics (waves, currents), morphodynamics (erosion, accretion) and density and biomass of the macrobenthic bivalve Meretrix meretrix during the passage of this typhoon, on an intertidal flat on the Chinese coast. Our results showed that, in spite of the considerable distance from the storm center, the bed shear stress greatly exceeded the critical value for erosion, resulting in rapid erosion of approximately 10 cm and a nearly 50% reduction in both the density and the biomass of the clam species. Our findings suggest that if storms become more frequent and more intense in a future warmer climate, they may increase physical disturbances to intertidal flats and their benthic animal populations, even at great distances from storm centers.

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The effect of long‐term aerial exposure on intertidal mudflat erodibility

Cited by 10 publications

References 69 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

Mangrove forest drag and bed stabilisation effects on intertidal flat morphology

Effect of typhoon‐induced intertidal‐flat erosion on dominant macrobenthic species (Meretrix meretrix)

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