HR: 1330h
AN: NB33C-04    [Abstracts]
TI: The Potential Role of Secondary Circulation, Nutrient Transport, and Peat Accretion in Wavelength Evolution of the Ridge and Slough Landscape, Everglades, FL
AU: * Larsen, L G
EM: Laurel.Griggs@colorado.edu
AF: University of Colorado, 428 UCB, Boulder, CO 80309 United States
AB: The ridge and slough landscape is a crucial ecosystem that has been deteriorating since the drainage of the Everglades in the early 1900s. The landscape is characterized by interconnected open-water sloughs interspersed among sawgrass ridges, which are 2-3 feet higher than the bottom of the sloughs and elongated parallel to the pre-drainage flow. The self-organized patterning of this landscape features a characteristic wavelength of approximately 50 meters. An understanding of the mechanisms responsible for landscape creation and maintenance is currently lacking but necessary for effective restoration planning. In exploring the mechanisms potentially responsible for formation of the ridge and slough landscape, it is noteworthy that the heads of ridges are indistinguishable from the tails; that is, landforms do not take on the lemniscate-shaped, minimum drag form associated with formation through nutrient or sediment transport via the mean flow. Rather, ridges and sloughs, though larger in scale, are more similar in form to longitudinal furrows and bars, which, in rivers and tidal flats, are generated by secondary circulation. However, bedforms generated by secondary circulation would be expected to scale at a maximum with flow depth, which in the Everglades would result in an initial wavelength an order of magnitude smaller than the current wavelength of the landscape. In this poster, the possibility of wavelength evolution resulting from preferential nutrient transport towards transpiring sawgrass colonists on ridges and differential peat accretion is explored through a combined finite difference/cellular automata model. The model is initialized with topography corrugated at the expected scale of secondary circulation cells. At each time step, the probability of sawgrass colonization, based on ridge height, porewater nutrient content, and proximity to surrounding sawgrass stands, is calculated. Based on the resulting distribution of plants and the state of plant growth, surface and porewater flow fields are determined, and a phosphorus balance is performed on each cell. Calculation of peat accretion and oxidation based on plant biomass and distance to the water table determines the new topography, and the model advances to the next time step. Results of the effect of this process on biogeomorphic evolution of the ridge and slough landscape are presented.
DE: 1824 Geomorphology (1625)
DE: 1832 Groundwater transport
DE: 1851 Plant ecology
DE: 1890 Wetlands
DE: 9345 Large bodies of water (e.g., lakes and inland seas)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly