HR: 14:55h
AN: H33I-06    [Abstracts]
TI: River Delta Morphodynamics: Examples From Danube Delta
AU: * Giosan, L
EM: lgiosan@whoi.edu
AF: Woods Hole Oceanographic Institution, 360 Woods Hole Rd., Woods Hole, MA 02543 United States
AB: Morphodynamics of the open-coast Danube delta has been largely determined by the interaction between fluvial deposition and the strong southward wave-induced longshore transport. Morphological and facies asymmetry displayed by the marine lobes of the Danube delta indicate that a strong and sustained southward-directed longshore transport has been a persistent process along the delta shore. Coastal evolution on the adjacent non-deltaic coast is also strongly coupled to the delta morphodynamics via the longshore transport. Analysis of recent deltaic progradation of the youngest open-coast lobes of Danube delta indicates that river mouth morphodynamics is highly non-linear, involving multiple feedbacks between subaerial deltaic progradation, deposition on the subaqueous delta, current and wave hydrodynamics as well as wave-current interactions. First, a feedback loop is activated by the hydraulic groin effect of the river plume that leads to a mutually-sustained progradation of the updrift coast and subaqueous delta at the mouth. Second, the development of a shallow subaerial delta platform, strongly offset to the downdrift direction, helps dissipate waves reaching the platform, leading to entrapment of sediment on the platform. Third, increased flood-induced deposition on the subaqueous delta platform, followed by wave reworking, leads to recurrent emergence of barrier islands at its offshore edge; longshore transport is then channeled (i.e., intensified and guided) by the new coast along the barrier, leading to a rapid alongshore expansion of the subaqueous delta in the downdrift direction. Although the sedimentation processes are complex, the resulting morphology at the mouth exhibits a tendency to self-organize that is reflected and preserved by the facies architecture of wave-influenced lobes.
DE: 4219 Continental shelf processes
DE: 4243 Marginal and semienclosed seas
DE: 3020 Littoral processes
DE: 3022 Marine sediments--processes and transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting