Video Transects Reveal That Tidal Sand Waves Affect the Spatial Distribution of Benthic Organisms and Sand Ripples

Damveld, Johan Hendrik; Reijden, K.J. van der; Cheng, Chiu H.; Koop, Leo; Haaksma, L.R.; Walsh, Cameron; Soetaert, Karline; Borsje, Bastiaan Wijnand; Govers, Laura L.; Roos, Pieter C.; Olff, Han; Hulscher, Suzanne J.M.H.

doi:10.1029/2018gl079858

Cited by 38 publications

(57 citation statements)

References 50 publications

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“…Here we have set this thickness to a spatially uniform value of 0.5 m, which is generally larger than the bed forms over sand waves, although megaripples on sand wave crests can have wave heights of several tens of centimeters. Still, since in sand wave troughs ripples are usually much smaller or even absent (Damveld et al, 2018), it is likely that the modeled active layer thickness is overestimated in the model. Importantly, this thickness is related to the time scale of the sorting process (Roos, Hulscher, et al, 2007), where a larger thickness increases the time scale.…”

Section: Discussionmentioning

confidence: 99%

Horizontal and Vertical Sediment Sorting in Tidal Sand Waves: Modeling the Finite‐Amplitude Stage

et al. 2020

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The bed of coastal seas displays a large number of rhythmic bed features, of which sand waves are relevant to study from an engineering perspective. Sediments tend to be well sorted over these bed forms, which is so far poorly understood in terms of modeling of finite-amplitude sand waves. Using Delft3D, we employ bed stratigraphy and consider four different grain-size classes, which are normally distributed on the phi scale. The standard deviation (sortedness) is then varied, whereas the geometric mean grain size is kept constant. The results show that, typically, the crests of sand waves are coarser than the troughs. Residual flow causes net sedimentation on the leeside of the crest, and, consequently, the general sorting pattern is distorted. Since larger grains experience a larger settling velocity, they are deposited on the upper lee slope, whereas the smaller grains are found on the lower lee slope. Due to sand wave migration, also, the internal structure of the sand wave is revealed, which follows the same sedimentation pattern as the lee slope surface. These results qualitatively agree with sorting patterns observed offshore. The sorting processes lead to longer wavelengths and lower wave heights, as a function of standard deviation. This relates to the dampening effect of suspended sediment transport for fine grains. Finally, it appears that the modeled wave heights fall in the same range as observations in the North Sea. These results are valuable for, for example, predicting the morphological response after engineering activities and determining suitable aggregates for sand extraction.

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Section: Discussionmentioning

confidence: 99%

Horizontal and Vertical Sediment Sorting in Tidal Sand Waves: Modeling the Finite‐Amplitude Stage

et al. 2020

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“…Our model shows that the biomass of benthic organisms and sand waves develop in antiphase (or close to), which is supported by observations in the field. Baptist et al [1], and more recently, Damveld et al [17] observed that organisms living on top of the seabed as well as within, occur much more frequently in sand waves troughs compared to the crests. Moreover, preliminary results from a recent field campaign show that various abiotic parameters, which are good predictors for the occurrence of benthic organisms, such as silt content and permeability, also show phase related patterns over sand waves [15].…”

Section: Comparison To Field Datamentioning

confidence: 99%

“…These variations are often related to geomorphological patterns of various dimensions [1,42,44,46]. In particular, Damveld et al [17] found that benthic organisms (benthos) occurred in much higher densities in sand wave troughs compared to the crests. Additionally, previous studies have shown that benthos in turn may significantly affect the local hydro-and sediment dynamics, and thereby the morphological development [29,55].…”

Section: Introductionmentioning

confidence: 99%

Modelling the two-way coupling of tidal sand waves and benthic organisms: a linear stability approach

Damveld¹,

Roos²,

Borsje³

et al. 2019

Environ Fluid Mech

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We use a linear stability approach to develop a process-based morphodynamic model including a two-way coupling between tidal sand wave dynamics and benthic organisms. With this model we are able to study both the effect of benthic organisms on the hydro-and sediment dynamics, and the effect of spatial and temporal environmental variations on the distribution of these organisms. Specifically, we include two coupling processes: the effect of the biomass of the organisms on the bottom slip parameter, and the effect of shear stress variations on the biological carrying capacity. We discuss the differences and similarities between the methodology used in this work and that from 'traditional' (morphodynamics only) stability modelling studies. Here, we end up with a 2 × 2 linear eigenvalue problem, which leads to two distinct eigenmodes for each topographic wave number. These eigenmodes control the growth and migration properties of both sand waves and benthic organisms (biomass). Apart from hydrodynamic forcing, the biomass also grows autonomously, which results in a changing fastest growing mode (FGM, i.e. the preferred wavelength) over time. As a result, in contrast to 'traditional' stability modelling studies, the FGM for a certain model outcome does not necessarily have to be dominant in the field. Therefore, we also analysed the temporal evolution of an initial bed hump (without perturbing biomass) and of an initial biomass hump (without perturbing topography). It turns out that these local disturbances may trigger the combined growth of sand waves and spatially varying biomass patterns. Moreover, the results reveal that the autonomous benthic growth significantly influences the growth rate of sand waves. Finally, we show that biomass maxima tend to concentrate in the region around the trough and lee side slope of sand waves, which corresponds to observations in the field.

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“…On the regional scale (i.e., Southern Bight of the North Sea) environmental conditions such as morphology, sediment characteristics, chlorophyll-a, bed shear stress, and salinity are found to explain the benthic species distribution best [17]. Locally, at meso-scale (i.e., tidal ridges and sand wave systems) troughs and crests house different communities [18][19][20][21][22]. At the small scale of nearshore bars, the number of species increases with depth and distance offshore, with a possible increased species diversity in the troughs of the bar system [23].…”

Section: Introductionmentioning

confidence: 99%

Benthic Species Distribution Linked to Morphological Features of a Barred Coast

Holzhauer

Borsje

Dalfsen³

et al. 2019

JMSE

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The composition of benthic species communities in the nearshore zone is closely related to the hydrodynamic and morphodynamic conditions. Sustainable management of the coastal ecosystem requires knowledge about the natural dynamics as well as human-induced changes on the ecosystem. To improve our knowledge of the benthic species distribution along a dissipative sandy shore with multiple breaker bars, an extensive dataset was collected in the nearshore zone of the barrier islands Ameland and Schiermonnikoog in the Dutch North Sea. From 2010 to 2014, every year, approximately 180 grab samples along 18 cross-shore transects were collected and analyzed for sediment characteristics and macrobenthic species composition. Mixed-effect-models and partial redundancy analysis were used to analyze the importance of morphological features (i.e., slopes, bar crests, and troughs) as an explanatory variable for the benthic species distribution. The results indicate that the morphological features in themselves explain three times more variation than the environmental parameters used. This demonstrates the importance of morphological features as a factor in explaining the distribution of benthic species communities in the nearshore. Detailed information on morphological features is easy to obtain from bathymetry maps or visual inspection. Incorporating morphological features in species distribution models will therefore help to improve sustainable management of our valuable sandy coastal systems.

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Video Transects Reveal That Tidal Sand Waves Affect the Spatial Distribution of Benthic Organisms and Sand Ripples

Cited by 38 publications

References 50 publications

Horizontal and Vertical Sediment Sorting in Tidal Sand Waves: Modeling the Finite‐Amplitude Stage

Horizontal and Vertical Sediment Sorting in Tidal Sand Waves: Modeling the Finite‐Amplitude Stage

Modelling the two-way coupling of tidal sand waves and benthic organisms: a linear stability approach

Benthic Species Distribution Linked to Morphological Features of a Barred Coast

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