Abstract
Prolonged in-situ measurements and satellite images were analyzed to investigate storm-driven dispersal patterns of fluvially derived fine sediment in the Atchafalaya Bay/Shelf during winter storms and tropical cyclones and how they remotely influence fine-sediment distribution of an offshore sand shoal. It was revealed that storm-driven offshore advection coinciding with sediment re-suspension transports re-suspended sediment and fine sediment from the river and from the bay to the inner shelf regardless of the storm types. However, we found that the process leading to the dispersal varies with the types of storms, their intensity and tracks. On the shelf, while tropical cyclones were capable of bringing re-suspended sediment to the surface, winter storms limited the extent of sediment suspension up to approximately 10 m above the bottom. Thus, only the sediment suspension on the shallower part of the shelf (< 10 m in depth) was expected to contribute significantly to sediment dispersal during winter storms. The estimated mass of re-suspended sediment in the bay during a single storm event accounted for more than a quarter of the total sediment mass from the river in the entire summer; more than half of the re-suspended sediment was expected to be transported to the shelf. It was also found that the storm-driven advection plays an important role in the migration of the fine sediment plumes to the offshore shoal. Despite the patchy and ephemeral nature of fine sediment on the shoal, the findings have established an important link between storm-driven sediment dispersal and sediment dynamics of ecologically sensitive shoals along the Louisiana coast. (c) 2019 Elsevier B.V. All rights reserved.
