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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #171933


item Wilson, Christopher

Submitted to: Journal of Great Lakes Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2004
Publication Date: 4/1/2005
Citation: Wilson, C.G., Matisoff, G., Whiting, P.J., Klarer, D.M. 2005. Transport of fine sediment through a wetland using radionuclide tracers: Old Woman Creek, OH. Journal of Great Lakes Research 31(1): 56-67.

Interpretive Summary: Coastal wetlands tend to trap more sediment delivered from the watershed than they let pass through to the downstream lakes and oceans. The Old Woman Creek, OH, wetland (OWC) is no exception to this rule. It traps 47% of the annual incoming sediment from the watershed. Because wetlands trap sediment, they eventually fill completely with sediment. However, OWC has not filled with sediment yet because, during individual storm events, the wetland exports previously delivered sediment that had settled on the wetland bottom. Budgets of sediment and two naturally-occurring unstable elements were developed during a single storm event to understand this fact. The wetland exported 118 ± 2% of the delivered sediment. The wetland exported only 93 ± 3% and 74 ± 2% of the two other elements. The ratios of the two elements compared to one another in the delivered sediment and the sediment on the wetland bottom suggest that 26 ± 20% of the exported sediment came from the wetland bottom. The wetland trapped only 13 ± 3% of the sediment delivered to it during the runoff event. Thus, the OWC wetland traps the majority of the delivered sediment over the long-term but sometimes it releases sediment from the wetland bottom that had previously settled.

Technical Abstract: The Old Woman Creek estuary (OWC), a coastal wetland in Ohio, traps 47% of incoming suspended sediment and has a sedimentation rate of ~1 cm/yr. Persistence of the OWC wetland and other coastal wetlands with high sedimentation rates seems problematic unless some previously trapped sediment is exported from the wetland. Suspended sediment, 7Be, and 210Pbxs budgets for a single runoff event in the OWC wetland were developed to understand short-term sediment dynamics. The budgets were balanced by subtracting the sum of the imports from the sum of the exports and attributing the difference to either deposition on, or resuspension from, the wetland bed. The wetland exported 118 ± 2%, 93 ± 1%, 74 ± 2% of the delivered sediment, 210Pbxs, and 7Be, respectively, during the studied event. The 7Be/210Pbxs ratios of the total suspended solids and bed sediment were distinct from one anther and used to quantify the relative proportions of recently delivered and resuspended bed material in the sediment efflux from the wetland. The 7Be/210Pbxs ratios suggest that 26 ± 20% of the sediment efflux was resuspended from the bed. While the wetland trapped 13 ± 3% of the sediment it received during the runoff event, resuspension and removal of previously deposited sediment in the wetland was sufficiently large to result in a net loss of sediment from the wetland during the event. Thus, the Old Woman Creek wetland is a sediment sink over the long-term, but can be a net exporter of sediment during single events.