HR: 09:30h
AN: OS11D-07    [Abstracts]
TI: Dispersal of Fluvial Sediment in the Adriatic Sea, Italy
AU: * Harris, C K
EM: ckharris@vims.edu
AF: Virginia Institute of Marine Science, Route 1208, Greate Road, Gloucester Point, VA 23062 United States
AU: Sherwood, C R
EM: csherwood@usgs.gov
AF: US Geological Survey, Woods Hole Field Center, Woods Hole, MA 02543
AU: Signell, R P
EM: rsignell@usgs.gov
AF: US Geological Survey, Woods Hole Field Center, Woods Hole, MA 02543
AB: The Adriatic Sea provides a setting for contrasting a range of sediment dispersal processes. The largest single source of sediment, the Po River, delivers an estimated 15 million tons of sediment annually, much during floods that last for several weeks. South of the Po, several rivers drain smaller catchments in the Apennine Mountains, delivering 32 millions tons of sediment annually. Sediment from these Apennine rivers is delivered during floods that tend to last only a few days. Field observations have shown that the fine-grained sediment delivered by the Po River is predominantly packaged as fast-settling flocculates, whereas the Apennine rivers deliver slowly-settling unflocculated material. The distribution of material from the Po and Apennine rivers results from dispersal patterns that differ due to the sediment properties of fluvial material, the timescales of sediment delivery, and along coast variations in wave and current speeds. A three-dimensional numerical sediment transport model is used to evaluate dispersal paths of fine-grained fluvial sediment delivered to the Adriatic Sea, Italy for September, 2002 -- May, 2003. These calculations estimate resuspension, transport, delivery from fluvial sources, and net deposition. Currents are driven by buoyancy forcing and winds. Wave bottom orbital velocities are based on predictions made using the SWAN wave model. Predicted patterns of fluvial deposition are similar to those observed in Holocene accumulation maps. Deposition is thickest near the Po River mouth, and the Po sediment bed extends alongshore towards the south. Sediment is preferentially deposited on the northern side of the Gargano Peninsula, tens of kilometers south of any major fluvial source. On a regional scale, sediment flux occurs preferentially during northeasterly wind events because these both enhance waves and intensify the western Adriatic coastal current. Sediment from the Po River is initially deposited near the river mouth, whereas sediment from Apennine rivers can traverse long distances during floods. Po River sediment, is, however, remobilized by energetic waves soon after delivery and some of the material may reach depocenters offshore of the Gargano Peninsula within a single storm season.
DE: 4211 Benthic boundary layers
DE: 4243 Marginal and semienclosed seas
DE: 4558 Sediment transport
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting