Consequences of limited sediment supply for long-term evolution of offshore tidal sand waves, a 3D model perspective

Nnafie, A.; Krabbendam, J.M.; de Swart, H.E.

doi:10.1016/j.margeo.2023.107148

Cited by 1 publication

(1 citation statement)

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“…Huthnance (1982aHuthnance ( , 1982b implemented scarcity as a non-erodible layer and hypothesized that scarcity was required for equilibrium cross-sections to exist, but later studies with more realistic hydrodynamics (e.g., Roos et al, 2004; showed that this was not the case. Regarding other bedforms, sand scarcity was shown to decrease height and width, increase wavelength and three-dimensionality in shape, and affect the migration rate of tidal (Nnafie et al, 2023;Porcile et al, 2017) and fluvial dunes (Dreano et al, 2010;Endo, 2016;Kleinhans et al, 2002;Tuijnder et al, 2009;Vah et al, 2020). However, these bedforms are driven by flow circulations in the vertical plane (Hulscher, 1996;Paarlberg et al, 2009;Vittori & Blondeaux, 2020) rather than the residual circulations in the horizontal plan that drive tidal sandbanks (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Modeling the Cross‐Sectional Dynamics of Tidal Sandbanks in Sediment‐Scarce Conditions

van Veelen,

Roos,

Hulscher

2024

JGR Earth Surface

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Tidal sandbanks are large‐scale dynamic bedforms that consist of sandy sediment. They have been observed in shallow seas with varying sediment supply, including sediment‐scarce environments like the Flemish Banks, Zeeland Banks, and Norfolk Banks. However, we do not yet understand how scarcity affects sandbank evolution. Therefore, we have developed an idealized nonlinear process‐based model with the aim of studying cross‐sectional shape and migration under sediment‐scarce conditions. Scarcity is included through a non‐erodible layer from which no sediment can be entrained. Our results show that bank height and width decrease when the sediment budget decreases. The bank height is more sensitive to scarcity than bank width. Furthermore, sand scarcity decreases (and may even reverse) bank asymmetry and increases migration rate when a residual current is present. The migration rate attains a maximum for a specific sediment budget, which is controlled by the ratio of the cross‐sectional area of the sandbank and the tide‐averaged sediment flux. Our findings show that sandbank dynamics are strongly affected by scarcity, which is critical for seas with receding sediment stocks (e.g., through extraction).

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