Determining Dredge-Induced Turbidity and Sediment Plume Settling within an Intracoastal Waterway System

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boat wake, channel dredging, dredge plume, estuaries, Florida, seagrasses, sediment transport, settling velocity, submerged aquatic vegetation (SAV)

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The intracoastal waterway (IWW) is a continuous navigation channel that often extends across seagrass beds and other sensitive habitats throughout the Gulf and Atlantic Coast estuaries of the United States. Turbidity increase associated with an IWW dredging operation in west-central Florida and subsequent dredge plume subsidence were measured with optical backscatter sensors and acoustic Doppler velocimeters, which also measured in situ wave and current conditions. The field experiments were conducted over a dense seagrass bed. Sediment in the study area is dominantly composed of fine, well-sorted quartz sand, typical of Florida estuaries. The dredge plume temporally increased the turbidity to more than 400 mg/L around a midwater depth. The settling of the dredge plume and sediment resuspension were calculated with commonly used empirical formulas for noncohesive sediments and compared with field observations. The relatively energetic conditions generated by frequent boat wake did not result in significant resuspension and remixing of the suspended sediments and had minor influence on the settling time of the dredge plume. Findings from this study may provide information on understanding potential impacts of dredging on seagrass beds.

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Journal of Coastal Research, v. 33, issue 2, p. 243-253