Numerical modelling of the migration direction of tidal sand waves over sand banks

Leenders, S.; Damveld, Johan Hendrik; Schouten, Jan Joost; Hoekstra, R.; Roetert, T.J.; Borsje, Bastiaan Wijnand

doi:10.1016/j.coastaleng.2020.103790

Cited by 12 publications

(17 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There are more degrees of freedom in a 3D model, such as the transverse slope terms and non-linear interactions between bed level perturbations in the longitudinal and transverse directions [49]. Leenders et al [12] have studied the migration of sand waves over a sloping bathymetry using linear stability analysis, which resulted in a large variation in migration rates, depending on the location on the slope. However, finite amplitude sand waves have not been studied from a 3D point of view and this remains a topic of future research.…”

Section: Discussionmentioning

confidence: 99%

“…If the tidal signal is asymmetrical due to the presence of residual currents or overtides, the convergence of sand is out of phase with the bed perturbations, causing the sand waves to migrate [11]. The model by Hulscher [10] was extended in terms of the solution method and several physical processes; for an overview see, e.g., Besio et al [6] and Leenders et al [12] and references therein. The formation processes were identified with the use of linear stability analysis [13].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Modelling the Past and Future Evolution of Tidal Sand Waves

Krabbendam,

Nnafie,

de Swart

et al. 2021

JMSE

View full text Add to dashboard Cite

This study focuses on the hindcasting and forecasting of observed offshore tidal sand waves by using a state-of-the-art numerical morphodynamic model. The sand waves, having heights of several meters, evolve on timescales of years. Following earlier work, the model has a 2DV configuration (one horizontal and one vertical direction). First, the skill of the model is assessed by performing hindcasts at four transects in the North Sea where sand wave data are available of multiple surveys that are at least 10 years apart. The first transect is used for calibration and this calibrated model is applied to the other three transects. It is found that the calibrated model performs well: the Brier Skill Score is ’excellent’ at the first two transects and ’good’ at the last two. The root mean square error of calculated bed levels is smaller than the uncertainty in the measurements, except at the last transect, where the M2 is more elliptical than at the other three transects. The calibrated model is subsequently used to make forecasts of the sand waves along the two transects with the best skill scores.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Modelling the Past and Future Evolution of Tidal Sand Waves

Krabbendam,

Nnafie,

de Swart

et al. 2021

JMSE

View full text Add to dashboard Cite

show abstract

“…Megaripple migration, however, could considerably affect S. spinulosa reef patchiness and stability. Migration patterns are thought to be site-specific (Knaapen et al, 2005) and affected by morphological bedforms at larger scales (Leenders et al, 2021). Intertidal megaripples with similar amplitude and wavelength as encountered in the Brown Bank area were shown to migrate around 1 m week −1 (van der Wal et al, 2017).…”

Section: Discussionmentioning

confidence: 98%

Conservation Implications of Sabellaria spinulosa Reef Patches in a Dynamic Sandy-Bottom Environment

et al. 2021

View full text Add to dashboard Cite

Biogenic reefs form biodiversity hotspots and are key components of marine ecosystems, making them priority habitats for nature conservation. However, the conservation status of biogenic reefs generally depends on their size and stability. Dynamic, patchy reefs may therefore be excluded from protection. Here, we studied epibenthos and epifauna density, richness, and community composition of patchy, dynamic Sabellaria spinulosa (ross worm) reefs in the North Sea. This study was conducted by comparing boxcore (endobenthos) and video transect (epifauna) data from two research campaigns in 2017 and 2019 to the Brown Bank area on the Dutch Continental Shelf, where S. spinulosa reefs were first discovered in 2017. The Brown Bank area is characterized by dynamic, migratory bedforms at multiple scales which potentially affect biogenic reef stability. We showed that S. spinulosa habitats had a patchy distribution and alternated with habitats comprised of plain sand. Average S. spinulosa habitat patch size was 5.57 ± 0.99 m and 3.94 ± 0.22 m in 2017 and 2019, respectively (mean ± SE), which especially in 2019 closely resembled the small-scale megaripple bedforms. Contrary to the endobenthos communities that were unaffected by S. spinulosa, epifauna density and species richness were at least two times higher in S. spinulosa habitats compared to sandy habitats, resulting in different community compositions between the two habitat types. We showed that S. spinulosa persisted in the area for almost 2 years. Although the stability of individual patches remained unclear, we demonstrated that even patchy biogenic reefs may promote density and local biodiversity of mobile, epibenthic species, very likely as a result of increased habitat heterogeneity provided by reef habitat patches. This indicates that patchy biogenic reefs that occur in dynamic environments may also have high ecological value and their conservation status should be (re)considered to ensure their protection.

show abstract

“…Studies on the long‐term, finite‐height dynamics of tidal sand waves using numerical models have only been considered in a 2DV context, with models comprising the vertical and the horizontal direction perpendicular to the crests (e.g., Campmans et al., 2018; Krabbendam et al., 2021; Van Gerwen et al., 2018, and references therein). So far, 3D simulations were only obtained for short times, that is, one or two tidal cycles (Leenders et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

“…What has been studied is the influence of background topography on sand wave migration: both Ma et al (2018) and Zhou et al (2022) observed that sand waves migrate in opposite directions on both sides of a sand bank. Using a numerical 3D model, Leenders et al (2021) related such bi-directional migration patterns over a sand bank to alterations in residual flow patterns caused by the interaction of the tidal flow with the tidal sand bank. Their morphological model study focused on the initial stage when sand waves have small amplitudes with respect to the water depth and they did not consider the finite-height regime.…”

mentioning

confidence: 99%

Background Topography Affects the Degree of Three‐Dimensionality of Tidal Sand Waves

Krabbendam,

Nnafie,

Borsje

et al. 2023

JGR Earth Surface

View full text Add to dashboard Cite

Offshore tidal sand waves on the sandy bed of shallow continental shelf seas are more three‐dimensional (3D) in some places than others, where 3D refers to a pattern that shows variations in three spatial directions. Such sand waves have crestlines that meander, split or merge. The degree of three‐dimensionality seems to vary especially when large‐scale bedforms, such as tidal sand banks, are present underneath the sand waves. Understanding this behavior is important for offshore activities, such as offshore windfarm construction or the maintenance of navigation channels. In this study, the degree of three‐dimensionality of sand waves at five sites in the North Sea is quantified with a new measure. Results show that tidal sand waves on top of tidal sand banks are more two‐dimensional (2D) than those on bank slopes or in open areas. These differences in sand wave pattern are supported by numerical simulations performed with a new long‐term sand wave model. The primary cause of these differences is attributed to the deflection of tidal flow over a sand bank, which causes sand wave crests to be more aligned with the bank at its top than at its slopes. It is subsequently made plausible that the different patterns result from the competition between two known mechanisms. These mechanisms are nonlinear interactions between sand waves themselves (SW‐SW interactions) and nonlinear interactions between sand banks and sand waves (SB‐SW interactions). On bank tops, SB‐SW interactions favor a 2D pattern, while SW‐SW interactions, which elsewhere produce a 3D pattern, are less effective.

show abstract

Numerical modelling of the migration direction of tidal sand waves over sand banks

Cited by 12 publications

References 31 publications

Modelling the Past and Future Evolution of Tidal Sand Waves

Modelling the Past and Future Evolution of Tidal Sand Waves

Conservation Implications of Sabellaria spinulosa Reef Patches in a Dynamic Sandy-Bottom Environment

Background Topography Affects the Degree of Three‐Dimensionality of Tidal Sand Waves

Contact Info

Product

Resources

About