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Accession Number 5003538

Title Response of coastal ecosystems to sea-level rise: assessing wetland elevation changes,

potential for submergence, and management options

Project Description This project will accomplish the following objectives: (1) establish a comprehensive geographic

network of elevation monitoring sites on Federal coastal wetlands to give an advance warning of

change, (2) determine the long-term potential for submergence of Federal coastal wetlands

through modeling, (3) establish standard measurement protocols among the coastal wetland

research community to make data from different sites comparable and allow for evaluation of

global trends in the vulnerability of coastal wetlands to submergence, (4) determine the critical

subsurface processes (biological, hydrological, and geological) controlling elevation change in

coastal wetlands to enable development of appropriate management strategies, and (5) determine

the impact of current wetland management and restoration practices on wetland elevation changes

and the ability of the wetlands to build vertically at a pace equal to relative sea-level rise. These

objectives will be accomplished by use of a field approach developed by Cahoon and colleagues

which is based on direct and simultaneous measures of vertical accretion and soil elevation

change. Elevation is measured from temporary benchmarks using a Sedimentation-Erosion Table

(SET). Vertical accretion is measured from visible soil marker horizons established at the same

time as the initial elevation readings. This approach allows us to not only (1) quantitatively and

directly test whether or not vertical accretion is a good surrogate for elevation change, and (2)

calculate an elevation deficit if accretion and elevation are not equal, but to also (3) calculate the

amount of subsidence (accretion minus elevation change) in the top few meters of the substrate

(i.e., shallow subsidence) and (4) distinguish the effects of surface (e.g., sediment deposition and

erosion) versus subsurface processes (e.g., soil compaction, root growth-decomposition, pore

water storage) on wetland elevation. This latter ability is of particular importance to wetland

managers when developing a management strategy to accomodate future increases in sea level.

Findings will be used in models to predict the long-term (>50 years) response of wetland elevation

to sea-level rise.

Keywords accretion, coastal wetlands, compaction, elevation, monitoring, sea-level rise,

sedimentation-erosion table, submergence, subsidence, wetland management, wetland


Principal Donald R Cahoon, USGS Patuxent Wildlife Research Center:;


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