A new fluorescent tracers experiment improves understanding of sediment dynamics along the Arcay Sandspit (France)
Tóm tắt
A new fluorescent tracers experiment, based on the injection of three distinct tracers at different elevations along a beach profile, was carried out in the vicinity of the Arcay Sandspit (western France), aiming at a better understanding of its rapid growth. The results confirmed that longshore transport was the dominant process in the development of the sandspit. The cross-shore integration of the longshore transport, deduced from the tracers analysis, revealed important differences in transport rates along the beach profile. In the upper part of the beach (beach berm), transport rates were one order of magnitude higher than in the lower part. These differences are associated with increases in wave height and wave incidence with the rising tide, combined with the steepening of the beach slope along the profile. The increase in wave height and incidence at high tide can be explained by a strong decrease in bottom friction, subsequent to the higher water level. This analysis provides a new description of the long-term development of the Arcay Sandspit, involving fast transport of coarse sand within the upper part of the beach over a base of fine sand moving much more slowly.
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