Author(s): Nan Wang; Zaijin You; Qin Chen
Linked Author(s):
Keywords: Morphodynamic modeling; Sediment transport; Fourleague Bay; Mississippi River Delta; Delft3D
Abstract: Fourleague Bay (FLB) has been recognized as an ideal location for investigating the effects of fine sediment diversion strategies in the Mississippi River Delta (MRD). In this study, we utilized the Delft3D flow-wave model to conduct a thorough analysis of hydrodynamics, sediment transport, and the resultant morphological shifts in FLB. Our goal was to deepen the understanding of how fine sediments disperse within this environment. The comparative analysis of our model's output against actual measurements—including water levels, wave characteristics, current speeds, and rates of morphological change—demonstrates a high level of accuracy, confirming the model’s ability to simulate the essential dynamics and sediment transport phenomena of the location. The simulated morphological change rates show strong spatial variability in FLB in 2015 and 2016. Notably, erosion was predominant in the southern and eastern bayous and near the bay's perimeter, likely influenced by the local bathymetric contours. The findings also indicate that sediment deposition was heightened in the eastern and western marsh areas during periods of elevated river flow and robust winds, notably in January and March 2016. Aligning the release of river water with periods of increased atmospheric activity could thus bolster and encourage marshland expansion. In a more granular analysis of sediment dynamics, we categorized eight types of cohesive sediment within our model for FLB. This helped discern the origins of the sediments. Our examination of sediment contributions at station T1 from May to June 2015 revealed that the primary influx of sediments during calm conditions stemmed from external sources, particularly the Atchafalaya Bay/River. Conversely, in stormy weather marked by significant wind-driven waves, locally resuspended sediments were the predominant contributors within the bay. In summary, the combined Delft3D flow-wave model, which is corroborated by direct field observations, is effective in replicating the actual conditions of water levels, wave activity, currents, and sediment dynamics in Fourleague Bay. The model, having been confirmed to work well, can now be used to improve how sediment
Year: 2024