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Dredging
About: Dredging is a research topic. Over the lifetime, 3300 publications have been published within this topic receiving 28325 citations.
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TL;DR: In this article, the authors examined increased turbidity and light attenuation in the suspended sediment plumes created by hydraulic clam dredging in Chesapeake Bay, MD, U.S.A. The plume characteristics were determined primarily by bottom sediment type and water depth.
Abstract: Increased turbidity and light attenuation (Kd) in the suspended sediment plumes created by hydraulic clam dredging were examined in Chesapeake Bay, MD, U.S.A. Turbidity andKdvalues were measured along transects in areas with and without dredge plumes. The turbidity andKdof individual plumes were tracked as they returned to background levels using both Lagrangian and Eulerian techniques. Existing aerial photographs and a geographical information system (ARC/INFO) were used to examine plume sizes and dredge boat locations in relation to bathymetry.
Hydraulic clam dredging produced plumes with significantly higher turbidity and light attenuation compared to background values. Plume characteristics were determined primarily by bottom sediment type and water depth. The greatest increase in turbidity and light attenuation occurred when dredges operated in shallow water (<1·0 m) where bottom sediments had increased amounts of silt and clay. Plume turbidity andKddissipated exponentially over time. The initial change in concentration of suspended sediments was rapid as the coarse sediments settled to the bottom. The rate of plume decay slowed as diffusion and resuspension acted on the finer sediments remaining in suspension. Some Lagrangian rates of plume dissipation were faster than Eulerian rates due to resuspension in shallow waters. Examination of aerial photographs indicated that 72% of the dredge boats digitized in the Chester River were operating in less than 2 m water. The area of a plume measured per boat in the Chester River was highly variable, ranging from 0·01 to 0·64 m2.
43 citations
TL;DR: In this paper, a core sampling of the eastern (control) and western (disturbed) sides of Beaufort Inlet, North Carolina, twice before and once 8 months after a large disposal revealed significant coarsening of sediments and associated changes to assemblages of benthic macroinvertebrates in response to the perturbation.
Abstract: Dredged materials from maintenance and deepening of inlets on coastal barriers are typically transported for disposal in deep water or on land. An alternative is to treat dredged materials as a resource, placing them on the ebb-tidal delta or subtidal shoals at depths where they are retained within the long-shore transport system and can nourish eroding down-drift beaches. Deposition of sediments onto subtidal shoals may, however, bury and selectively kill populations of benthic invertebrates, or indirectly alter assemblages by modifying sediment characteristics. Core sampling of the eastern (control) and western (disturbed) sides of Beaufort Inlet, North Carolina, twice before and once 8 months after a large (660,000 m3) disposal revealed significant coarsening of sediments and associated changes to assemblages of benthic macroinvertebrates in response to the perturbation. Impacts to sediments and macroinverte-brates were closely correlated and, although greatest where sediment was directly depo...
43 citations
01 Jan 1982
TL;DR: In Europe, echosounders are being replaced by in situ density measurement as the means to define navigable depth and to monitor or control dredging as discussed by the authors, which allows time series of mass deposition to be constructed, dredging schedules to be optimised, and productivity to be increased.
Abstract: Field observations show fine sediment suspensions often have a mobile, high-concentration layer adjacent to the sea bed. Stationary suspensions which have time-varying acoustic and mechanical properties develop from these layers. In these circumstances, conventional survey echosounders can not provide unambiguous information on sea bed altitude relevant to safe navigation and optimum dredging practices. In Europe, echosounding is being replaced by in situ density measurement as the means to define navigable depth and to monitor or control dredging. Repeated in situ density surveys allow time series of mass deposition to be constructed, dredging schedules to be optimised, and productivity to be increased. Techniques may then be developed to trap sediment in designated sites where stationary pumping systems remove spoil automatically at an optimum density.
43 citations
TL;DR: A short-term experiment to assess the ecological impact of a hydraulic blade dredge on a maerl community was carried out during November 2001 in the Clyde Sea area on the west coast of Scotland as mentioned in this paper.
Abstract: A short-term experiment to assess the ecological impact of a hydraulic blade dredge on a
maerl community was carried out during November 2001 in the Clyde Sea area on the west
coast of Scotland. A fluorescent sediment tracer was used to label dead maerl, which was then
spread out on the surface of sediment to act as a proxy for living maerl. The fauna collected by
the dredge was dominated by the bivalves Dosinia exoleta and Tapes rhomboides, which
were found to be intact. The target razor clams Ensis spp. were caught in low numbers, which
reflected the low abundance of this genus within the maerl habitat. The hydraulic dredge
removed, dispersed and buried the fluorescent maerl at a rate of 5.2 kgm2 and suspended a
large cloud of sediment into the water column, which settled out and blanketed the seabed to a
distance of at least 8m either side of the dredge track. The likely ecological consequences of
hydraulic dredging on maerl grounds are discussed, and a case is made for protecting all
maerl grounds from hydraulic dredging and establishing them as reservoirs to allow for the
recruitment of commercial bivalve populations at adjacent fished sites.
42 citations
TL;DR: Wang et al. as discussed by the authors conducted simulated research of internal loading and collecting and analyzing the samples from the lakes were carried out before and after dredging in polluted suburb lakes, Wuli Lake (Wuxi City) and Xuanwu Lake (Nanjing City), which showed that dredging can inhibit internal loadings in a certain degree in a short term.
Abstract: Simulated research of internal loading and collecting and analyzing the samples from the lakes were carried out before and after dredging in polluted suburb lakes, Wuli Lake (Wuxi City) and Xuanwu Lake (Nanjing City). The research results showed that dredging can inhibit internal loadings in a certain degree in a short term. The discrepancy of dredging effect and technical level, namely dredging quality, by different dredging methods will result in a difference of control of lake internal loadings. The internal loadings’ reversion will gradually appear along with the biogeochemical processes, including suspended particle precipitation, hydrodynamic disturbance and microbio-transformation. The reversion rate mainly depends on the dredging method and the change of interfacial processes on the newborn surface layer. The higher nutrient contents and organic matter in the sediment will enhance water-sediment interfacial processes and nutrients regeneration. It is very important to study the physicochemical and biological character of lacustrine sediments before dredging for determining the dredging methods and predicting their environmental effect.
42 citations