Plant stiffness and biomass as drivers for drag forces under extreme wave loading: A flume study on mimics

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

doi:10.1016/j.coastaleng.2016.07.004

Cited by 67 publications

(54 citation statements)

References 43 publications

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“…; Paul et al . ). Unsurprisingly, AGB, canopy height and cover were reduced in the presence of livestock, with a general trend of stronger effects at higher stocking density or duration of grazing (Figs b and ) and within forb‐dominated plots (Fig.…”

Section: Discussionmentioning

confidence: 97%

“…Vegetated coastal regions reduce wave energy more effectively than bare mudflats (M€ oller et al 1999;Shepard, Crain & Beck 2011), with taller, denser vegetation being most effective (M€ oller et al 2014;Paul et al 2016). Unsurprisingly, AGB, canopy height and cover were reduced in the presence of livestock, with a general trend of stronger effects at higher stocking density or duration of grazing (Figs 3b and S3) and within forb-dominated plots (Fig.…”

Section: Vegetation and Coastal Protectionmentioning

confidence: 92%

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Livestock grazing alters multiple ecosystem properties and services in salt marshes: a meta‐analysis

Davidson

Fowler

Skov

et al. 2017

Journal of Applied Ecology

117

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Summary The far‐reaching impacts of livestock grazing in terrestrial grasslands are widely appreciated, but how livestock affect the structure and functions of sensitive coastal ecosystems has hitherto lacked synthesis. Grazing‐induced changes in salt marshes have the potential to alter the provision of valuable ecosystem services, such as coastal protection, blue carbon and biodiversity conservation. To investigate how livestock alter soil, vegetation and faunal properties in salt marshes, we conducted a global meta‐analysis of ungulate grazer impacts on commonly measured ecosystem properties (498 individual responses from 89 studies). We also tested stocking density, grazing duration, grazer identity, continent and vegetation type as potential modifiers of the grazing effect. The majority of studies were conducted in Europe (75) or the Americas (12), and investigated cattle (43) or sheep (22) grazing. All measures of above‐ground plant material (height, cover, above‐ground biomass, litter) were decreased by grazing, potentially impairing coastal protection through diminished wave attenuation. Soil carbon was reduced by grazing in American, but not European marshes, indicating a trade‐off with climate regulation that varies geographically. Additionally, grazing increased soil bulk density, salinity and daytime temperature, and reduced redox potential. Biodiversity responses depended on focal group, with positive effects of grazing on vegetation species richness, but negative effects on invertebrate richness. Grazing reduced the abundance of herbivorous invertebrates, which may affect fish and crustaceans that feed in the marsh. Overall vertebrate abundance was not affected, but there was provisional evidence for increases over a longer duration of grazing, potentially increasing birdwatching and wildfowling opportunities. Synthesis and applications. Our results reveal that the use of salt marshes for livestock production affects multiple ecosystem properties, creating trade‐offs and synergies with other ecosystem services. Grazing leads to reductions in blue carbon in the Americas but not in Europe. Grazing may compromise coastal protection and the provision of a nursery habitat for fish while creating provisioning and cultural benefits through increased wildfowl abundance. These findings can inform salt marsh grazing management, based on local context and desired ecosystem services.

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Section: Discussionmentioning

confidence: 97%

Section: Vegetation and Coastal Protectionmentioning

confidence: 92%

Livestock grazing alters multiple ecosystem properties and services in salt marshes: a meta‐analysis

Davidson

Fowler

Skov

et al. 2017

Journal of Applied Ecology

117

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“…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, ). On the other hand, the S. alterniflora stiffness is much higher in comparison to the stiffness of those more flexible species, and it might result in neglecting the bending angle under these hydrodynamic conditions (Paul et al, ). As stated by Maza et al (), the stems of this cordgrass act like a cantilever, and therefore, they do not align with the flow and have larger impact on the waves.…”

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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“…Wave energy dissipation by vegetation (hereafter referred as WDV ) is affected by incident wave height ( H , Méndez and Losada, 2004;Bradley and Houser, 2009 ), wave period ( T , Augustin et al, 2009;Suzuki et al, 2012 ), the ratio of water depth to vegetation height in the water ( h/h v , Ysebaert et al, 2011;Yang et al, 2012 ), drag coefficient ( C D , Henry et al, 2015;Losada et al, 2016a,b ), stiffness ( Bouma et al, 2005;Luhar et al, 2017;Paul et al, 2016 ) and stem frontal area of plants per unit height (i.e. N * b v , N is the number of stems per unit area and b v is the stem diameter, Augustin et al, 2009;Fonseca and Cahalan, 1992;Nepf, 2012Nepf, , 1999Ozeren et al, 2014 ).…”

Section: Introductionmentioning

confidence: 99%

Deriving vegetation drag coefficients in combined wave-current flows by calibration and direct measurement methods

Chen

Yan

et al. 2018

Advances in Water Resources

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Coastal vegetation is efficient in damping incident waves even in storm events, thus providing valuable protections to coastal communities. However, large uncertainties lie in determining vegetation drag coefficients (C D), which are directly related to the wave damping capacity of a certain vegetated area. One major uncertainty is related to the different methods used in deriving C D. Currently, two methods are available, i.e. the conventional calibration approach and the new direct measurement approach. Comparative studies of these two methods are lacking to reveal their respective strengths and reduce the uncertainty. Additional uncertainty stems from the dependence of C D on flow conditions (i.e. wave-only or wave-current) and indicative parameters, i.e. Reynolds number (Re) and Keulegan-Carpenter number (KC). Recent studies have obtained C D-Re relations for combined wave-current flows, whereas C D-KC relations in such flow condition remain unexplored. Thus, this study conducts a thorough comparison between two existing methods and explores the C D-KC relations in combined wave-current flows. By a unique revisiting procedure, we show that C D derived by the direct measurement approach have a better overall performance in reproducing both acting force and the resulting wave dissipation. Therefore, a generic C D-KC relation for both wave-only and wave-current flows is proposed using direct measurement approach. Finally, a detailed comparison of these two approaches are given. The comprehensive method comparison and the obtained new C D-KC relation may lead to improved understanding and modelling of wave-vegetation interaction.

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Plant stiffness and biomass as drivers for drag forces under extreme wave loading: A flume study on mimics

Cited by 67 publications

References 43 publications

Livestock grazing alters multiple ecosystem properties and services in salt marshes: a meta‐analysis

Livestock grazing alters multiple ecosystem properties and services in salt marshes: a meta‐analysis

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

Deriving vegetation drag coefficients in combined wave-current flows by calibration and direct measurement methods

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