HR: 15:25h
AN: H33L-08    [Abstracts]
TI: Vegetation, sea level rise, and the morphological stability of wetland landscapes.
AU: * Kirwan, M L
EM: mkirwan@usgs.gov
AF: U.S. Geological Survey, Patuxent Wildlife Research Center, Dept. Environmental Sciences, University of Virginia, PO Box 123, Charlottesville, VA 22904, United States
AU: Murray, A B
EM: abmurray@duke.edu
AF: Nicholas School of the Environment, Duke University, Dept. Earth and Ocean Sciences, Box 90229, Durham, NC 27708, United States
AU: Guntenspergen, G R
EM: glenn_guntenspergen@usgs.gov
AF: U.S. Geological Survey, Patuxent Wildlife Research Center, Dept. Environmental Sciences, University of Virginia, PO Box 123, Charlottesville, VA 22904, United States
AB: Tidal wetland landscapes -extensive, vegetated marshes and the channel networks that wind through them- provide a striking example of a geomorphological system in which the physical and biological processes cannot be addressed separately. Vegetated marsh platforms and intertwining channel networks are thoroughly coupled; the dynamic marsh elevation relative to high-tide level determines the volume of tidal flow through the channels, and channels distribute the water and sediment that facilitates plant growth and therefore marsh accretion. We have developed a numerical model that couples biologically influenced platform accretion with hydrodynamically driven channel network erosion, and have used it to simulate marsh system response to sea-level rise. In the model, increased inundation on the platform stimulates biomass productivity and therefore tends to increase: sediment deposition rates, resistance to channel bank erosion, and the elevation of vegetated surfaces relative to sea level. Establishment of vegetation plays a critical role in developing, and maintaining, a horizontal platform incised by a well defined channel network. In model simulations with intact vegetation, a 10-fold increase in the rate of sea-level rise results in a stable platform, and a channel network morphology that is undetermined by platform elevation and the volume of water flowing through the channels. Temporary disturbance to vegetation, however, leads to rapid and widespread erosion of the channel network. In some model experiments, an increase in the intensity of disturbance converts broad and expansive marshland into highly dissected platforms characterized by numerous marsh islands and interior ponds. In this case, temporary disturbance in one part of the system (i.e. the vegetated platform) leads to a change in physical conditions in another part of the system (i.e. channel edges), and an irreversible loss of vegetation. Vegetated portions of an episodically disturbed platform accrete more rapidly than rates of relative sea level rise, giving submerging marshland the appearance of maintaining elevation relative to sea-level.
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0442 Estuarine and nearshore processes (4235)
DE: 1641 Sea level change (1222, 1225, 4556)
DE: 1813 Eco-hydrology
DE: 1824 Geomorphology: general (1625)
SC: Hydrology [H]
MN: 2007 Fall Meeting