Influence of Key Environmental Drivers on the Performance of Sediment Diversions

Abstract

A Delft3D morphodynamic model for Barataria Bay, Louisiana, USA is used to quantify a plausible range of land change in response to a proposed sediment diversion under a range of environmental drivers. To examine the influence of environmental drivers, such as Mississippi River water hydrographs, mineral and organic sediment loading, sea level rise rates, subsidence, and a projected implementation (or operation) date, 240 multi-decadal (2020–2100) numerical experiments were used. The diversion was assumed to begin operation in 2025, 2030, or 2035. The experiments revealed persistent benefits of the sediment diversion through 2100. Start data of 2025 result in a median net positive land change of 32 km2 by 2100; whereas the 90th, and 10th percentiles are 69 and 10 km2. A delay in the operation date of the diversion to 2030 or 2035 would reduce the net positive land change by approximately 15–20% and 20–30%, respectively.

Impact of water loss on sustainability of the Mississippi River channel in its deltaic reach

“…Our results show that even the loss in stream power induced by the increased water losses below RK48 in recent decades is causing shoaling that is likely linked to the need for dredging of the deepwater navigation channel moving further upstream in recent years (US Army Corps of Engineers (USACE), 2018a). In addition to relative sea level rise, the loss of containment‐dredging link could be exacerbated in the future by authorized sediment diversions upstream for coastal restoration and protection unless offset by closure or modification of other exits (Allison & Meselhe, 2010; Meselhe et al, 2022). Conversely, wetter conditions in the Mississippi basin (Lewis et al, 2019) while offsetting stream power loss through exits below New Orleans to a small degree, would also likely lead to an increase in the frequency of maximum floods that initiate new containment failures.…”

Modeling of water waves and sediment transport using physics-based and machine learning methods

“…The project allows river water and sediments from the Mississippi and Atchafalaya Rivers to flow into degrading wetlands by building structures and channels (Protection and others, 2017). In recent years, significant effort has been made to understand the MRD's sediment transport processes and wetland sustainability (e.g., Meselhe et al, 2012;Rosen and Xu, 2014;Yuill et al, 2016;Elsey-Quirk et al, 2019;Bomer et al, 2019;Meselhe et al, 2021).…”