Vegetation-wave interactions in salt marshes under storm surge conditions

Rupprecht, Franziska; Möller, Iris; Paul, Maike; Kudella, Matthias; Spencer, T.; Wesenbeeck, Bregje K. van; Wolters, Guido; Jensen, Kai; Bouma, T.J.; Miranda-Lange, Martin; Schimmels, Stefan

doi:10.1016/j.ecoleng.2016.12.030

Cited by 109 publications

(91 citation statements)

References 65 publications

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“…For instance, Maza et al () and Bradley and Houser () found that smaller waves were more attenuated for similar water depths when interacting with Puccinela maritima and Thalassia testudinum . Later, Rupprecht et al () demonstrated that orbital velocities and water depths played an important role on the bending angle, and therefore in the frontal area resisting the flow. More flexible stems might be bent by high orbital velocities, extending them in the flow direction, and therefore reducing the actual length that is affecting the flow (Losada et al, ).…”

Section: Discussionmentioning

confidence: 99%

Wave Attenuation by Spartina Saltmarshes in the Chesapeake Bay Under Storm Surge Conditions

et al. 2019

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This study investigates the capacity of a Spartina alterniflora meadow to attenuate waves during storm events based on field observations in the Chesapeake Bay. These observations reveal that environmental conditions including the ratio between water depth and plant height (hr), the ratio between wave height (HS) and water depth, and current directions impact the wave height decay. Further, we present empirical representations of the bulk drag coefficient (Cd) as a function of the Keulegan‐Carpenter (KC) and Reynolds (Re) numbers, and the hr ratio. When applying the distinction between current directions, this representation exhibits better agreement when using the Re (ρ2 = 54%) and hr (ρ2 = 77%) than with the KC (ρ2 = 39%). Furthermore, we show that the representation of Cd can be improved by using a hr‐based modified Re and KC formulation, yielding correlations of 76% (modified Re) and 78% (modified KC). The proposed expressions are validated during another storm and predicted HS computed within the marsh results in a root‐mean‐square error of 0.014 m, overestimating the largest HS (0.22 m) by 18%. Finally, these expressions are applied to several hypothetical sea conditions. Under similar vegetation characteristics, HS of 1.55 and 0.8 m (close to a 10,000‐ and 100‐year recurrence interval storm) are attenuated by 50% and 70%, respectively, at 250 m from the marsh edge. This study provides evidence that validates the saltmarsh wave attenuation capacity during storms, quantifies this attenuation, and supports the transferability of the existing formulas in the literature across similar coastal marshes.

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Section: Discussionmentioning

confidence: 99%

Wave Attenuation by Spartina Saltmarshes in the Chesapeake Bay Under Storm Surge Conditions

et al. 2019

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“…However, to avoid an overestimation of the wave height reduction for relatively long foreshores, the processes wind input (due to Snyder et al (1981)) and whitecapping (due to Komen et al (1984)) are added. All these model descriptions correspond with the implementations in the spectral wave model SWAN (Booij et al, 1999).If the wave-induced bending stresses exceed the plant's flexural strength, the stem will fold or break near the bottom (Rupprecht et al, 2017). The stem breakage model developed in Vuik et al (2018) is implemented in the model framework of Fig.…”

Section: Modeling Of Foreshore Effectsmentioning

confidence: 99%

Assessing safety of nature-based flood defenses: Dealing with extremes and uncertainties

Vuik

Vuren

Borsje

et al. 2018

Coastal Engineering

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Vegetated foreshores adjacent to engineered structures (so-called hybrid flood defenses), are considered to have high potential in reducing flood risk, even in the face of sea level rise and increasing storminess. However, foreshores such as salt marshes and mangrove forests are generally characterized by relatively strong temporal and spatial variations in geometry and vegetation characteristics (e.g., stem height and density), which causes uncertainties with regards to their protective value under extreme storm conditions. Currently, no method is available to assess the failure probability of a hybrid flood defense, taking into account the aforementioned uncertainties. This paper presents a method to determine the failure probability of a hybrid flood defense, integrating models and stochastic parameters that describe dike failure and wave propagation over a vegetated foreshore. Two dike failure mechanisms are considered: failure due to (i) wave overtopping and (ii) wave impact on revetments. Results show that vegetated foreshores cause a reduction in failure probability for both mechanisms. This effect is more pronounced for wave impact on revetments than for wave overtopping, since revetment failure occurs at relatively low water levels. The relevance of different uncertainties depends on the protection level and associated dike height and strength. For relatively low dikes (i.e., low protection levels), vegetation remains stable in design conditions, and plays an important role in reducing wave loads. In case of higher protection levels, hence for more robust dikes, vegetation is less important than foreshore geometry, because of expected stem breakage of the vegetation under these more extreme conditions. The integrated analysis of uncertainties in hydraulic loads, dike geometry and foreshore characteristics in this paper enables the comparison between nature-based flood defenses and traditionally engineered solutions, and allows coastal engineers to design hybrid flood defenses worldwide.

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“…The dynamic motion of vegetation changes the flow and produces eddies which, in turn, alter the flow forcing on the blade and blade motion. The blade motion due to flexibility reduces the relative velocity between flow and vegetation as well as the frontal area, resulting in a reduced drag that decreases velocity attenuation and wave attenuation in the vegetation meadow (Abdolahpour et al, 2018;Bouma et al, 2005;Houser et al, 2015;Mullarney & Henderson, 2010;Paul et al, 2012;Riffe et al, 2011;Rupprecht et al, 2017;Zeller et al, 2014). Numerical models have been developed to solve a force balance equation for the vegetation motion, considering gravity, buoyancy, structural damping, bending stiffness as restoring forces, as well as drag and inertia as driving forces (Ikeda et al, 2001;Leclercq & de Langre, 2018;Luhar & Nepf, 2016;Zeller et al, 2014;Zhu & Chen, 2015).…”

Section: Introductionmentioning

confidence: 99%

Mechanisms for the Asymmetric Motion of Submerged Aquatic Vegetation in Waves: A Consistent‐Mass Cable Model

et al. 2020

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Submerged aquatic vegetation (SAV) provides primary products for the food web, as well as shelter and nursery for many juvenile species. SAV can also attenuate waves, stabilize the seabed, and improve water quality. These environmental services are influenced by the dynamic motion of SAV. In this paper, a consistent‐mass cable model was developed to investigate flow interaction with a flexible vegetation blade. Compared with previous vegetation models, the cable model showed improvements in simulating blade motions in waves with and without currents, especially for “second‐normal‐mode‐like” blade motion. Wave asymmetry would cause blade motion to be asymmetric. However, asymmetric blade motion may also occur in symmetric waves. Results indicate that the asymmetric blade motion in symmetric waves is induced by two major mechanisms: (i) the spatial asymmetry of the encountered wave orbital velocities (wave motion relative to blade) due to blade displacements and (ii) the asymmetric action on the blade by vertical wave orbital velocities. Consequently, the blade motion is asymmetric even underneath symmetric waves unless (i) blade length ( l) is much smaller than the wavelength ( lfalse/L≪1), (ii) blade length is much smaller than the water depth ( lfalse/h≪1) in finite water depth waves, or (iii) water depth is much smaller than the wavelength ( hfalse/L≪1). Peak asymmetric blade motion occurs as lfalse/L increases to a critical value. The peak asymmetry increases with wave height and blade length but decreases with increasing blade flexural rigidity. Blade motion characteristics play an important role in wave‐vegetation interaction, wave‐driven currents, wave‐attenuation capacity, breakage of vegetation and ecosystem services.

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Vegetation-wave interactions in salt marshes under storm surge conditions

Cited by 109 publications

References 65 publications

Wave Attenuation by Spartina Saltmarshes in the Chesapeake Bay Under Storm Surge Conditions

Wave Attenuation by Spartina Saltmarshes in the Chesapeake Bay Under Storm Surge Conditions

Assessing safety of nature-based flood defenses: Dealing with extremes and uncertainties

Mechanisms for the Asymmetric Motion of Submerged Aquatic Vegetation in Waves: A Consistent‐Mass Cable Model

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