Dispersion of disposed dredged slurry in the meso-tidal Changjiang (Yangtze River) Estuary |
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| Authors: | Jiaxue Wu James T Liu Huanting Shen Shuying Zhang |
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| Institution: | aState Key Laboratory of Marine Geology, School of Ocean and Earth Science, Tongji University, 1239 Siping Road, Shanghai 200092, China;bInstitute of Marine Geology and Chemistry, National Sun Yat-sen University, Kaohsiung 804-24, Taiwan;cState Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China;dShanghai Acoustics Laboratory, Academia Sinica, 456 Xiao Mu Qiao, Shanghai 200032, China |
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| Abstract: | To understand the dispersal pattern of sediment plume and its controlling processes, a field experiment of concentrated slurry dispersal created by a dredger was conducted in the Changjiang (Yangtze River) Estuary during the 2002 flood season. An acoustic suspended sediment concentration profiler and an acoustic Doppler profiler were deployed to simultaneously observe suspended sediment concentrations (SSC) and tidal currents at the pre-selected sections shortly following the release of dredged materials. Water sampling, grab sampling and shallow coring were simultaneously carried out to obtain the SSC and grain-size texture. High-resolution SSC profiler observations showed that two distinct sediment plumes (middle level- and near-bed plumes) occurred during the intermediate tidal phase between the spring and neap due to differential settling of the sediment mixture, whereas only a benthic plume occurred due to rapid flocculation settling during the neap tide. Three subsequent stages can be identified during the dispersal of the sediment plume: (1) initially stable stage before the release; (2) unstable stage shortly following the release as a settling cloud; and (3) stable stage after the formation of a primary lutocline or a benthic plume. Enhanced mixing due to oscillatory shear flows could raise only the elevation of the lutocline in the slurry, but could not enhance the transport capacity of suspension. In the presence of high concentration, the fate of bottom sediment plume was controlled by the bottom stress, independent of the interfacial mixing. |
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| Keywords: | sediment plume lutocline mixing open-water disposal Changjiang (Yangtze) Estuary |
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