Abstract

The beneficial use of dredged material (BUDM) for wetland restoration improves coastal wetland resilience and conserves coastal natural infrastructure. Tools, such as biophysical models help coastal managers to assess habitat vulnerability and plan restoration. In this study, the Marsh Equilibrium Model (MEM) will be utilized combined with observed data to predict future conditions and evaluate potential marsh restoration via the BUDM in Mobile Bay, Alabama. A range of site conditions and restoration strategies will be considered and the impacts on dredged material management area (DMMA) volumes will be evaluated. Wetland restoration via thin-layer placement (TLP) of dredged material (DM) restores marsh elevation to combat sea level rise (SLR) and conserves fill capacity in DMMAs. A simplified mapping approach to assess this type of restoration will be demonstrated using wetland area and DM sources to determine the coastal United States wetland area to which it could be further applied. The mapping exercise revealed that 6,240 km2 of US wetlands were suitable for restoration and sediment resources exist to conduct this type of restoration from navigational dredging. The further development of a spatial application of the MEM is needed to provide an operational tool for managers and refine these restoration estimates.

Highlights

  • Wetlands are one of the most valuable ecosystems on the planet, which provide ecosystem services, such as flood control, shoreline stabilization and protection, and biodiversity support (Zedler and Kercher 2005)

  • The organic content was from 3% to 39% and the mineral fraction was from 61% to 97%

  • Sediment accretion rates at Blakeley Island, Mobile, Alabama, slightly outpaced recent rates of relative SLRs that were measured by National Oceanic and Atmospheric Administration (NOAA) but were lower than the USACE medium and high 100-year SLR projections, which indicated the vulnerability to submergence and requisite of restoration

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Summary

Introduction

Wetlands are one of the most valuable ecosystems on the planet, which provide ecosystem services, such as flood control, shoreline stabilization and protection, and biodiversity support (Zedler and Kercher 2005). The extent of wetlands in the United States has declined to below half the area before European settlement, which is due to land use conversion for agriculture and development (Dahl 1990; Dahl et al 1991) and is further projected to decline through conversion to open water faced with sea level rises [(SLRs) Craft et al 2009]. With accelerated rates of SLRs, coastal wetlands that do not have sufficient sediment and space to migrate might transition to subtidal environments, which results in ecosystem services losses. The relative global salt marsh loss by 2100 is projected to be as high as 45%, if provided with enough migration space and sediment supply the wetland extent could potentially expand (Craft et al 2009; Schuerch et al 2018). Even under future scenarios where the wetland extent increases, widespread or complete local losses might occur in areas with negative sediment balances and a limited area for migration

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