Eulie, D.O.; Leonard, L., and Polk, M., . Sediment deposition and availability in riparian wetlands.
Coastal flooding and sea-level rise have the potential to negatively influence the ability of coastal wetlands to accumulate sediment, threatening the persistence of coastal wetlands. This study examines sediment availability, deposition rates, and elevation change in two types of tidally-dependent riparian wetlands to understand their ability to persist in the wake of rising sea level. Tidal marshes and riparian swamp habitats in blackwater and brownwater river systems were studied over a 32-month period between 2004 to 2007. Wetlands along the brownwater river system exhibited significantly greater and more variable deposition rates than those located along the blackwater river system (p < 0.05). The brownwater marsh lost −1.7 cm of elevation and the blackwater marsh lost −1.1 cm of elevation, while the brownwater swamp site had an increase of 7.0 cm and the blackwater swamp site exhibited an increase in elevation of 0.7 cm. Within the Cape Fear River Estuary, a combination of sediment availability, organic content, and wetland type (tidal brackish marshes, riparian freshwater swamp forests) are what most strongly influenced patterns of deposition but are strongly temporally and spatially influenced. Marshes in the Cape Fear River are losing elevation, while riparian swamps are, at the time of this study, maintaining their current elevation. Coastal tidal wetlands are under increasing pressure from climate change, sea-level rise, and urban development resulting in vertical drowning. Tidal marshes in the Cape Fear River are not able to maintain elevation, and riparian swamp forests may also be unable to as the magnitude of these pressures increase.