Wave-induced sediment transport at the small tidal inlet 'Slufter' of Texel, the Netherlands
Klein Breteler, R.
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In September and October 2008 a field campaign was executed at the small tidal inlet ‘Slufter’ at Texel, the Netherlands. The aim is to improve our understanding of small tidal inlet systems. Measurements were done on hydrodynamics, sediment transport and (changes in) morphology. This thesis focuses on the relative importance of wave-induced cross- and longshore sediment transport processes in the breaker zone under normal conditions and on the wave-induced cross-shore transport processes on the spit-like platform (beach flat) during inundation of the inland basin under storm and spring tide conditions (Hs,off = 4-5 m). A storm occurred from 01/10 – 05/10 in which the basin of the inlet was completely inundated. During the inundation measurements were done on the spit like plat form (beach flat). The beach flat was subject to mean onshore velocities up to + 0.5 m/s. Highest waves entering the beach flat are in the far infragravity frequency band for the initial and peak flooding situations. Mean fluxes contribute to more than 75% of the net suspended sediment transport. Infragravity fluxes are dominant in the oscillatory velocity signal and are mainly onshore directed, contributing 15- 20% to the gross suspended transport. During low-moderate wave energy conditions measurements were done in the breaker zone. In the breaker zone infragravity waves were important for net offshore transport during low wave conditions (Hs,off < 1 m). Mean fluxes, which are mainly offshore directed by wave–driven undertow and high-frequency fluxes, which are mainly positive due to wave skewness contributed stronger to the net transport than low-frequency fluxes, but frequently were of opposite sign. For high wave conditions (Hs,off = 2-3 m), net suspended transport was dominated by offshore directed mean fluxes, partly compensated by higher onshore high-frequency fluxes. Low-frequency fluxes were only a fraction larger than for low wave conditions. Measured longshore currents show strong positive relation with the relative significant wave height. In the nearshore depth-integrated longshore fluxes are significantly higher than cross-shore fluxes.