Jackson Estuarine Laboratory

Rapid settling rates observed in sediments resuspended by boat wavesv over a tidal flat


A series of boat waves were directed across the tidal flat at varying water depths to (1) compare the different amounts of wave energy expended in each area of the tidal flat and (2) examine the post-boat wave effects on sediment resuspension and deposition.

More of the boat wave energy appears to be expended on the outer portion of the tidal flat (near low tide mark) than the inner portion when comparable water depths are observed. This observation coupled with the fact that the low tide area is under water for more of the tidal cycle than the upper tidal zone indicates that a decreasing energy gradient exists across the tidal flat. Because of this energy gradient, the outer portion of the tidal flat appears to be the most dynamic with alternate periods of resuspension and deposition. In contrast, the inner area is primarily depositional.

Near the low tide mark, sediments are easily resuspended—yet just as easily deposited. Their apparent high deposition rates are anomalous for the bottom sediment texture (pipette analysis) of the area and it is inferred the sediment particles are behaving more like low density aggregates may be local pelletization by benthic fauna or physical aggregation caused by reworking of the botton sediments by waves.

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Netherlands Journal of Sea Research

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