Strypsteen, G. and Rauwoens, P., 2023. Aeolian sand transport on a natural beach with shells and moist sand patches. Journal of Coastal Research, 39(4), 700–711. Charlotte (North Carolina), ISSN 0749-0208.

A field study was conducted on aeolian sand transport across a largely scattered shell pavement and moist sand patches on the upper beach of a natural beach-dune system in Koksijde, Belgium. Wind speed and direction were measured with a vertical array of eight cup anemometers and a wind vane. Sand transport was measured with a series of nine vertical arrays of Modified Wilson and Cook sand traps spaced at 20 m intervals, with the lowest trap 0.05 m above the surface. Fast-temporal changes in saltation intensity were measured with stacked saltiphones installed 0.05 and 0.15 m above the surface. The shells contributed significantly to the overall bed roughness as values between 20 and 100 mm were found in a shear velocity range between 0.3 and 0.75 m/s. Measured velocity profiles converge into a focal point that is two to six times higher than on bare sand surfaces. Downwind sand transport increased in the first 20 to 40 m from the high-water line and generally decreased by a factor of 10 to almost zero transport toward the dune toe. The fetch effect is responsible for the increase in transport, and the influence of surface shells and moist sand patches is responsible for the decrease. All vertical mass flux profiles were well fitted to the exponential decay function. Particle distribution above the bed was unaffected, whereas less flux was transported at the bed downwind. Variability in aeolian transport is cubic related to the variability in wind speed on the beach with shells. As a result of the shells and moist sand patches, mobile rippled sand strips or proto-dunes developed, which created a new source for aeolian sand to the foredunes.

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