HR: 09:45h
AN: OS11D-08    [Abstracts]
TI: Modeling Deposition by Wave-Supported Gravity Flows on the Po River Subaqueous Delta: From Seasonal Floods to Prograding Clinoforms
AU: * Friedrichs, C T
EM: cfried@vims.edu
AF: Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062 United States
AU: Scully, M E
EM: mscully@vims.edu
AF: Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062 United States
AB: A simple model for wave-supported gravity flows is applied to sediment deposition at time scales ranging from a single major flood to steady-state progradation of an equilibrium clinoform. The modeling approach, which limits sediment load via a critical Richardson number, is applicable to fine sediment transport near river mouths wherever wave energy is available to move abundant sediment offshore during floods. Results suggest this phemomena can account for the majority of the fall 2000 flood deposit mapped by EuroSTRATAFORM investigators in the vicinity of the Po subaqueous delta and also for the rate of delta progradation observed off the dominant Pila outlet of the Po over the last 150 years. Model results predict that convergence of down-slope sediment transport by wave-supported gravity flows increases with bed slope but decreases with slope gradient, such that greatest deposition occurs near where steep slopes first stop increasing with distance offshore. Thus on profiles which reach maximum steepness near shore, like those off Tolle-Gnocca-Goro mouths today or off the Pila mouth 150 years ago, gravity-driven deposition occurs in shallower water. Over time, if deposition overwhelms subsidence, the subaqueous delta becomes less steep near shore and steeper offshore, and the locus of deposition moves progressively into deeper water. If the subaqueous delta is prograding across a relatively flat shelf, the form of the prodelta eventually reaches an approximate equilibrium which progrades seaward as a unit. This has occurred off the Pila; but subsidence has likely overwhelmed deposition off the Tolle-Gnocca-Gorro, keeping steepest slopes and deposition in shallower water.
DE: 4255 Numerical modeling
DE: 4558 Sediment transport
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting