A parameterization of the wavelength of tidal dunes

Abstract

The idealized model of Besio et al. (On the formation of sand waves and sand banks. Journal of Fluid Mechanics 2006; 557: 1-17) is used to predict the wavelength of tidal dunes (sand waves) generated by tidal currents in estuaries and shallow seas. The predictions are then analysed and a formula is proposed to estimate the wavelength of tidal dunes as a function of the parameters of the problem. The wavelength of the dunes is found to increase when the water depth is increased and/or the strength of the tidal current is decreased. On the other hand, the size of the bottom material (if medium sand is considered) and the tidal ellipticity are found to have a relatively small influence on the length of the bottom forms. The formula proposed provides results which are consistent with field observations of different authors.

Spatially Varying Environmental Properties Controlling Observed Sand Wave Morphology

“…The correlations between sand wave frequency and water depth showed both positive and negative correlations, and this contrast may be explained from the varying wave impact. A previous modeling study without surface waves by Blondeaux and Vittori () found a negative relation between water depth and sand wave frequency. This is consistent with our results in the southern area.…”

“…Hulscher and Van den Brink (2001) and Van der Veen et al (2006) compared modeled sand wave occurrence to observations in the North Sea and found good agreement with important contributions for grain size, depth, and flow velocity. A modeling study by Blondeaux and Vittori (2011) showed that sand wavelengths increase for larger water depths and smaller tidal flow velocities. Grain size and ellipticity of the tide did not show clear relations to sand wavelength.…”

“…Grain size and ellipticity of the tide did not show clear relations to sand wavelength. A later study by Van Santen et al (2011) tested the conclusions of Blondeaux and Vittori (2011) against empirical data and also found the relation to tidal flow velocities. These results were not clear on relations with water depth, grain size, and ellipticity.…”

Do tidal sand waves always regenerate after dredging?

“…To explain the differences in sand wave behaviour at the three sites, we made use of available model studies that describe the initial formation of sand waves using linear stability analysis (Besio et al, 2003;Van Santen et al, 2011;Blondeaux and Vittori, 2011;Campmans et al, 2021). This theory assumes that initially there are only small bedforms, whose amplitudes grow or decay exponentially in time, with rates that are independent of their initial amplitude.…”

Long-term dynamics of tidal sand waves

“…Similarly, applied geometrical relations to compute the sand wave height from sand wavelengths that were obtained with a processbased model. Blondeaux and Vittori (2011) used a process-based model to compute the sand wavelength for different values of the water depth and tidal current amplitude. From these outcomes, they presented empirical relations between water depth, tidal current strength and the sand wavelength.…”