HR: 0800h
AN: H41B-0499    [Abstracts]
TI: Modeling Evolution of the Chandeleur Barrier Islands, Southeastern Louisiana: Initial Exploration of a Possible Threshold Crossing
AU: * Moore, L J
EM: laura.moore@oberlin.edu
AF: Oberlin College Department of Geology, 52 West Lorain St., Oberlin, OH 44074,
AU: List, J H
EM: jlist@usgs.gov
AF: U.S. Geological Survey Woods Hole Science Center, 384 Woods Hole Rd., Woods Hole, MA 02543,
AU: Williams, S J
EM: jwilliams@usgs.gov
AF: U.S. Geological Survey Woods Hole Science Center, 384 Woods Hole Rd., Woods Hole, MA 02543,
AB: Airborne photographic and lidar observations of the 72 km-long Chandeleur Island arc in southeastern Louisiana since August 2005 indicate that large volumes of sediment were removed from the islands during and following Hurricane Katrina and suggest that a return to pre-storm island configuration may be unlikely. Others have suggested, based on recent field observations, that the southern portion of the Chandeleur Islands may be showing signs of becoming an inner shelf shoal. In contrast to these observations, plentiful sand has been observed in the nearshore farther to the north; based on this finding it has been suggested that at least the northern portion of the Chandeleur Islands may be poised for recovery. Given the range of observations, it is unclear if Hurricane Katrina initiated a threshold crossing in the Chandeleurs causing the subaerial, landward- migrating barrier islands to begin evolving as submerged sand shoals. If a threshold crossing has not yet occurred and the Chandeleurs do recover from the impact of Hurricane Katrina, it remains uncertain how imminent a threshold crossing may be. To better understand the potential future evolution of the Chandeleur Islands and to assess the combination of factors that are likely to cause a threshold crossing in this environment, a series of initial model experiments are being conducted using the morphological-behavior model GEOMBEST. This model simulates the evolution of coastal morphology and stratigraphy resulting from changes in relative sea level and sediment supply, and provides insight into how barriers evolve over time scales ranging from decades to millennia. Vibracore logs, geophysical records, bathymetric surveys, and lidar surveys provide data necessary to design the model domain, while sediment budget studies, estimates of sea-level rise rates, and measurements of shoreline change rates provide input and calibration parameters. Late Holocene model runs simulate the evolution of 42 km-long North Chandeleur Island as it migrated from the distal end of the St. Bernard Delta to its modern position. Building on the late Holocene simulation, we present a series of initial, multi-decadal forward model experiments that assess the combination of factors, including relative sea-level rise rates, sediment supply rates, and geologic framework, that are likely to initiate a threshold crossing in the Chandeleur Islands.
DE: 1625 Geomorphology and weathering (0790, 1824, 1825, 1826, 1886)
DE: 1807 Climate impacts
DE: 1817 Extreme events
DE: 1847 Modeling
DE: 3020 Littoral processes
SC: Hydrology [H]
MN: 2007 Fall Meeting