Wave Damping by Kelp Vegetation

Dubi, Alfonse M.; Tørum, Alf

doi:10.1061/9780784400890.012

Cited by 39 publications

(31 citation statements)

References 2 publications

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“…A change or loss of these kelp beds would drastically affect coastal ecosystems as they provide habitat and shelter for epibionts and rich invertebrate and fish fauna (Schultze et al 1990). They also have a wave dampening effect which is important for coastal protection (Dubi & Tørum 1995). Since the late 1980s, there have been increasing and alarming reports of changes in the quantitative patterns of kelp communities along European coastlines and elsewhere.…”

Section: Introductionmentioning

confidence: 99%

Changes in depth distribution and biomass of sublittoral seaweeds at Helgoland (North Sea) between 1970 and 2005

Pehlke¹,

Bartsch²

2008

Clim. Res.

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Section: Introductionmentioning

confidence: 99%

Changes in depth distribution and biomass of sublittoral seaweeds at Helgoland (North Sea) between 1970 and 2005

Pehlke¹,

Bartsch²

2008

Clim. Res.

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“…Since extensive experimental data for a large array of cylinders exist only for steady flows [4, e.g.,], we rest content with time-independent C D and C M . Therefore, a time-invariant eddy viscosity, ν e = ν e (X i ), can be obtained from the energy balance argument by equating the time averages of E and P, 6) where the overbar denotes the average over a wave period T . A detailed derivation of equation stating the balance of mechanical energy over the volume of unit cell can be found in Mei et al [19].…”

Section: Eddy Viscosity For Two-dimensional Wavesmentioning

confidence: 99%

“…On the free surface, the kinematic boundary condition requires 6) where ζ denotes the free-surface displacement. For the dynamic conditions, we require that both the normal and tangential stresses vanish,…”

Section: Formulation For Infinitesimal Wavesmentioning

confidence: 99%

“…Because of its influence on coastal inundation, beach erosion and the ecological health of coastal waters, the interaction of vegetation and storm waves or tsunamis have also received increasing attention. For example, wave flume simulation of kelps, seagrasses, and coastal trees have been conducted by [1,3,6,7,23,29,33,34,38,40,42], among others. Mathematical models starting from macro-scale (wavelength-scale) equations have been proposed by many (e.g., [5,16,22,17] etc.).…”

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confidence: 99%

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Waves of intermediate length through an array of vertical cylinders

2013

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We report a semi-analytical theory of wave propagation through a vegetated water. Our aim is to construct a mathematical model for waves propagating through a lattice-like array of vertical cylinders, where the macro-scale variation of waves is derived from the dynamics in the micro-scale cells. Assuming infinitesimal waves, periodic lattice configuration, and strong contrast between the lattice spacing and the typical wavelength, the perturbation theory of homogenization (multiple scales) is used to derive the effective equations governing the macro-scale wave dynamics. The constitutive coefficients are computed from the solution of micro-scale boundary-value problem for a finite number of unit cells. Eddy viscosity in a unit cell is determined by balancing the time-averaged rate of dissipation and the rate of work done by wave force on the forest at a finite number of macro stations. While the spirit is similar to RANS scheme, less computational effort is needed. Using one fitting parameter, the theory is used to simulate three existing experiments with encouraging results. Limitations of the present theory are also pointed out.

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“…Schultze et al, 1990;Dubi and Tørum, 1994). Thus, changes in abundance and extent of these forests might have tremendous effects on coastal ecosystems, their production, functionality, and diversity.…”

Section: Introductionmentioning

confidence: 99%

Predicting spatial kelp abundance in shallow coastal waters using the acoustic ground discrimination system RoxAnn

Mielck

Bartsch

Hass

et al. 2014

Estuarine, Coastal and Shelf Science

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a b s t r a c tKelp forests represent a major habitat type in coastal waters worldwide and their structure and distribution is predicted to change due to global warming. Despite their ecological and economical importance, there is still a lack of reliable spatial information on their abundance and distribution. In recent years, various hydroacoustic mapping techniques for sublittoral environments evolved. However, in turbid coastal waters, such as off the island of Helgoland (Germany, North Sea), the kelp vegetation is present in shallow water depths normally excluded from hydroacoustic surveys. In this study, single beam survey data consisting of the two seafloor parameters roughness and hardness were obtained with RoxAnn from water depth between 2 and 18 m. Our primary aim was to reliably detect the kelp forest habitat with different densities and distinguish it from other vegetated zones. Five habitat classes were identified using underwater-video and were applied for classification of acoustic signatures. Subsequently, spatial prediction maps were produced via two classification approaches: Linear discriminant analysis (LDA) and manual classification routine (MC). LDA was able to distinguish dense kelp forest from other habitats (i.e. mixed seaweed vegetation, sand, and barren bedrock), but no variances in kelp density. In contrast, MC also provided information on medium dense kelp distribution which is characterized by intermediate roughness and hardness values evoked by reduced kelp abundances. The prediction maps reach accordance levels of 62% (LDA) and 68% (MC). The presence of vegetation (kelp and mixed seaweed vegetation) was determined with higher prediction abilities of 75% (LDA) and 76% (MC). Since the different habitat classes reveal acoustic signatures that strongly overlap, the manual classification method was more appropriate for separating different kelp forest densities and low-lying vegetation. It became evident that the occurrence of kelp in this area is not simply linked to water depth. Moreover, this study shows that the two seafloor parameters collected with RoxAnn are suitable indicators for the discrimination of different densely vegetated seafloor habitats in shallow environments.

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Wave Damping by Kelp Vegetation

Cited by 39 publications

References 2 publications

Changes in depth distribution and biomass of sublittoral seaweeds at Helgoland (North Sea) between 1970 and 2005

Changes in depth distribution and biomass of sublittoral seaweeds at Helgoland (North Sea) between 1970 and 2005

Waves of intermediate length through an array of vertical cylinders

Predicting spatial kelp abundance in shallow coastal waters using the acoustic ground discrimination system RoxAnn

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