Modeling wetland transitions and loss in coastal Louisiana under scenarios of future relative sea-level rise

Reed, Denise J.; Wang, Yushi; Meselhe, Ehab; White, Eric

doi:10.1016/j.geomorph.2019.106991

Cited by 40 publications

(37 citation statements)

References 75 publications

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“…The latter is limited to a depth of few meters and includes hydrological alterations (e.g., drained soil due to marsh ditching), which might accelerate carbon oxidation and soil compaction. Because deep subsidence is weakly dependent on short‐term marsh processes, it is generally simulated as a boundary condition in salt marsh models (Fagherazzi et al, 2012; Reed et al, 2020). Explicitly accounting for subsidence in a process‐based manner might be opportune when considering long time scales, (at the scales of evolution of bays and deltas and their wetlands).…”

Section: Salt Marshes and Sea Level Risementioning

confidence: 99%

“…This elevation loss is defined as deep subsidence. One approach is to consider the gross sediment accumulation at the surface and separately include shallow and deep subsidence into the RSLR term (e.g., Reed et al, 2020). Another approach is to consider a net vertical accretion, in which the shallow subsidence is directly subtracted from the gross accretion, while the deep subsidence is considered separately.…”

Section: Salt Marshes and Sea Level Risementioning

confidence: 99%

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Salt Marsh Dynamics in a Period of Accelerated Sea Level Rise

et al. 2020

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Salt marshes are dynamic systems able to laterally expand, contract, and vertically accrete in response to sea level rise. Here, we present the grand challenges that need to be addressed to fully characterize marsh morphodynamics. The review focuses on physical processes and quantitative models. Without predictive models, it is impossible to determine the future marsh evolution under accelerated sea level rise. In these models, one of the challenges is to resolve both horizontal and vertical dynamics within the same framework. Vertically, the marsh has to accumulate enough material to contrast rising water levels. Horizontally, marsh erosion at the ocean side must be compensated by landward expansion in forests, lawns, and agricultural fields. The dynamics of the marsh‐upland boundary are still not fully understood and will require more research in the upcoming years. The complexity of marsh vegetation is seldom captured in predictive models of marsh evolution. More research is needed to understand the effects of each species or species assemblages on hydrodynamics and sediment transport. Here, we further advocate that a sediment budget resolving all sediment fluxes in a marsh complex is the most important metric of marsh resilience. Characterization of these fluxes will enable to connect salt marshes to other landforms and to unravel feedbacks controlling the evolution of the entire coastal system. Current models of marsh evolution rely on sparse data sets collected at few locations. Novel remote sensing techniques will provide high‐resolution spatial data that will inform a new generation of computer models.

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Section: Salt Marshes and Sea Level Risementioning

confidence: 99%

Section: Salt Marshes and Sea Level Risementioning

confidence: 99%

Salt Marsh Dynamics in a Period of Accelerated Sea Level Rise

et al. 2020

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“…This addition of the upwinding technique greatly increased the stability of salinity predictions. Further discussion and analysis of the ICM methodology, calibration, validation, model performance and analysis are provided in the Supplementary Materials as well as several peer reviewed articles [24][25][26][30][31][32][33][34] and technical reports [35][36][37][38][39][40][41].…”

Section: Methodsmentioning

confidence: 99%

“…The FWOA run maintains the same connections between the basins and Mississippi River as the current conditions simulation. However, the 50-year simulation includes the effects of the relative sea-level rise and the changing wetland landscape within the basins [33]. Under FWOA, all basins show an increase over time in the proportion of the basin in the 2-16 ppt range, and both Pontchartrain and Breton show an increase in the area >16 ppt by year 50.…”

Section: Simulations Of Future Conditions With Varying Levels Of Fresmentioning

confidence: 99%

“…It should be noted that in addition to the vegetation shifts over time and under different freshwater exchange scenarios, there is a marked decrease in the amount of wetland area throughout lower Barataria and lower Breton basins under this assumed relative sea level rise scenario. This conversion of wetland area to open water is a consequence of persistent inundation and salinity penetration due to the combined effects of eustatic sea level rise and subsidence [33].…”

Section: Modified Exchange Between the Mississippi River And Breton Smentioning

confidence: 99%

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Mitigating the Effects of Sea-Level Rise on Estuaries of the Mississippi Delta Plain Using River Diversions

White

Meselhe

Reed

et al. 2019

Water

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Using the Mississippi River as a tool for restoration has been a key element of restoration planning in Louisiana for decades. The results of allowing river water and sediment back into the coastal system are manifested in a number of places in present day Louisiana, with additional plans for large scale sediment and water diversions from the Mississippi River. Many previous numerical modeling studies have focused on sediment delivery to Louisiana estuaries. This study examines the effects of river diversions on salinity gradients in receiving estuarine basins. The Integrated Compartment Model, a planning-level model that simulates multi-decadal change in estuarine hydrodynamics and wetland systems under assumed sea-level rise scenarios, was used to assess the estuarine salinity gradient under potential management regimes. The simulations for current conditions are compared to a future 50-year simulation with additional diversions, as well as cases with a variety of diversion options. This modeling analysis shows that without additional action, 50-years of sea-level rise could result in substantial increases in salinity throughout the Mississippi Delta Plain estuaries. This can be largely offset with additional large river diversions which can maintain variable salinity gradients throughout the estuary basins.

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Modeling net ecosystem carbon balance and loss in coastal wetlands exposed to sea‐level rise and saltwater intrusion

Ishtiaq

Troxler

Lamb-Wotton

et al. 2022

Ecological Applications

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Coastal wetlands are globally important stores of carbon (C). However, accelerated sea‐level rise (SLR), increased saltwater intrusion, and modified freshwater discharge can contribute to the collapse of peat marshes, converting coastal peatlands into open water. Applying results from multiple experiments from sawgrass (Cladium jamaicense)‐dominated freshwater and brackish water marshes in the Florida Coastal Everglades, we developed a system‐level mechanistic peat elevation model (EvPEM). We applied the model to simulate net ecosystem C balance (NECB) and peat elevation in response to elevated salinity under inundation and drought exposure. Using a mass C balance approach, we estimated net gain in C and corresponding export of aquatic fluxes (FAQ$$ {F}_{\mathrm{AQ}} $$) in the freshwater marsh under ambient conditions (NECB = 1119 ± 229 gC m−2 year−1; FAQ = 317 ± 186 gC m−2 year−1). In contrast, the brackish water marsh exhibited substantial peat loss and aquatic C export with ambient (NECB = −366 ± 15 gC m−2 year−1; FAQ = 311 ± 30 gC m−2 year−1) and elevated salinity (NECB = −594 ± 94 gC m−2 year−1; FAQ = 729 ± 142 gC m−2 year−1) under extended exposed conditions. Further, mass balance suggests a considerable decline in soil C and corresponding elevation loss with elevated salinity and seasonal dry‐down. Applying EvPEM, we developed critical marsh net primary productivity (NPP) thresholds as a function of salinity to simulate accumulating, steady‐state, and collapsing peat elevations. The optimization showed that ~150–1070 gC m−2 year−1 NPP could support a stable peat elevation (elevation change ≈ SLR), with the corresponding salinity ranging from 1 to 20 ppt under increasing inundation levels. The C budgeting and modeling illustrate the impacts of saltwater intrusion, inundation, and seasonal dry‐down and reduce uncertainties in understanding the fate of coastal peat wetlands with SLR and freshwater restoration. The modeling results provide management targets for hydrologic restoration based on the ecological conditions needed to reduce the vulnerability of the Everglades' peat marshes to collapse. The approach can be extended to other coastal peatlands to quantify C loss and improve understanding of the influence of the biological controls on wetland C storage changes for coastal management.

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Modeling wetland transitions and loss in coastal Louisiana under scenarios of future relative sea-level rise

Cited by 40 publications

References 75 publications

Salt Marsh Dynamics in a Period of Accelerated Sea Level Rise

Salt Marsh Dynamics in a Period of Accelerated Sea Level Rise

Mitigating the Effects of Sea-Level Rise on Estuaries of the Mississippi Delta Plain Using River Diversions

Modeling net ecosystem carbon balance and loss in coastal wetlands exposed to sea‐level rise and saltwater intrusion

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