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Showing papers on "Dredging published in 2014"


Journal ArticleDOI
TL;DR: The aim of this study was to develop a risk-based decision-making framework for the selection of sediment dredging option, accounting for the economic, environmental and technical aspects of dredging, which is beneficial for dredging and sediment management industries.

34 citations


Journal ArticleDOI
TL;DR: To address concerns for protection of fishery resource occupying the harbor, sound pressure levels were examined at frequency bands of 50-1000 Hz and 100-400 Hz, the ranges where the majority of fishes without hearing specializations detect sound and the range of greatest sensitivity, respectively.
Abstract: Sound recordings were made of two dredging operations at hydrophone depths of 3 and 9.1 m at distances up to 1.2 km from the source in shallow waters (<15 m) of New York Harbor. Sound sources included rock fracturing by a hydraulic cutterhead dredge and six distinct sources associated with a mechanical backhoe dredging operation during rock excavation. To place sound emitted from these dredges in perspective with other anthropogenic sounds, recordings were also made of several deep-draft commercial vessels. Results are presented as sound pressure levels (SPLs) in one-third octave versus range across the 20 Hz to 20 kHz frequency band. To address concerns for protection of fishery resource occupying the harbor, SPL were examined at frequency bands of 50–1000 Hz and 100–400 Hz, the ranges where the majority of fishes without hearing specializations detect sound and the range of greatest sensitivity, respectively. Source levels (dB re 1 μPa-1 m rms) were back calculated using fitted regression (15LogR). The strongest sound sources (180–188.9 dB) were emitted by commercial shipping. Rock fracturing produced a source level of 175 dB, whereas six distinct sources associated with rock excavation had source levels ranging from 164.2 to 179.4 dB re 1 μPa-1 m (rms).

30 citations


Journal ArticleDOI
TL;DR: In this article, the authors used FVCOM to investigate the tidal discharges, flow asymmetries and sediment discharges of three channels and perform one-hundred-year-long morphological simulation.

29 citations


Journal ArticleDOI
TL;DR: A shift in composition towards species less susceptible to trace elements was observed, disclosing some individual taxa as potential indicators, and diatom:other groups ratio and benthic:pelagic diatom ratio were reliable indicators for the assessment of dredging induced changes.

29 citations


Journal ArticleDOI
TL;DR: In this paper, an approach is proposed to monitor sand-dredging activities using medium-resolution optical remote-sensing imagery, including 45 Landsat TM/ETM+ images from 2002 to 2012 and 140 HJ1A/B CCD images from 2009 to 2012.
Abstract: As the largest freshwater lake in China, Poyang Lake is suffering from declining water quality related to the excessive dredging of sand. Field supervision is difficult due to the size of the lake (>3000 km2, wet season) and limited human resources. In this study, an approach is proposed to monitor sand-dredging activities using medium-resolution optical remote-sensing imagery, including 45 Landsat TM/ETM+ images from 2002 to 2012 and 140 HJ1A/B CCD images from 2009 to 2012. The procedure for detecting dredging vessels involves three steps. (1) The entire image is segmented into different homogeneous partitions to overcome water body heterogeneity, and ships in each partition with different levels of water clarity are detected using three types of contrast box architecture. (2) Dredging vessels are then identified based on a spatial overlay analysis of ships and dredging plumes, which are extracted from remote-sensing imagery. (3) False alarms (FAs) of dredging vessels are screened according to the distri...

29 citations


Journal ArticleDOI
TL;DR: In this article, three research cruises were carried out in Polish waters of the Baltic Sea, NW of the Gulf of Gdansk, at a water depth of 15-17m.

28 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated changes in the spatial distribution and population structure of an exploited shellfish bed of Callista chione at a location of the northwestern Mediterranean Sea and analyzed its potential causes.

24 citations


Journal ArticleDOI
TL;DR: In this paper, a total of 184 surficial sediment samples were collected randomly at two sites during 8 sampling periods from April 2010 to March 2013; one site (defined as borrow site) was 2 km offshore and used as the dredging site for beach nourishment of nearby Hilton Head Island in Beaufort County, South Carolina, and the other site was 10 km offshore.
Abstract: Beach nourishment has been a strategy widely used to slow down coastal erosion in many beaches around the world. The dredging of sand at the borrow site, however, can have complicated physical, geological and ecological impacts. Our current knowledge is insufficient to make accurate predictions of sediment infilling in many dredging pits due to lack of detailed sediment data. Two sites in the sandy shoal southeast of Port Royal Sound (PRS) of South Carolina, USA, were sampled 8 times from April 2010 to March 2013; one site (defined as ‘borrow site’) was 2 km offshore and used as the dredging site for beach nourishment of nearby Hilton Head Island in Beaufort County, South Carolina, and the other site (defined as ‘reference site’) was 10 km offshore and not directly impacted by the dredging. A total of 184 surficial sediment samples were collected randomly at two sites during 8 sampling periods. Most sediments were fine sand, with an average grain size of 2.3 phi and an organic matter content less than 2%. After the dredging in December 2011–January 2012, sediments at the borrow site became finer, changing from 1.0 phi to 2.3 phi, and carbonate content decreased from 10% to 4%; changes in mud content and organic matter were small. Compared with the reference site, the borrow site experienced larger variations in mud and carbonate content. An additional 228 sub-samples were gathered from small cores collected at 5 fixed stations in the borrow site and 1 fixed station at the reference site 0, 3, 6, 9, and 12 months after the dredging; these down-core sub-samples were divided into 1-cm slices and analyzed using a laser diffraction particle size analyzer. Most cores were uniform vertically and consisted of fine sand with well to moderately well sorting and nearly symmetrical averaged skewness. Based on the analysis of grain size populations, 2 phi- and 3 phi-sized sediments were the most dynamic sand fractions in PRS. Mud deposition on shoals offshore of PRS presumably happens when offshore mud transport is prevalent and there is a following rapid sand accumulation to bury the mud. However, in this borrow site there was very little accumulation of mud. This will allow the site to be used in future nourishment projects presuming no accumulation of mud occurs in the future.

23 citations


Journal ArticleDOI
TL;DR: Experimental scallop dredging was conducted to assess the vulnerability of emergent epifauna on hard substrates as discussed by the authors, and the results highlight the role that substrate morphology might play in modifying the severity of dredging effects.
Abstract: Experimental scallop dredging was conducted to assess the vulnerability of emergent epifauna on hard substrates. Three sites were sampled before and after dredging to examine changes in the coverage of faunal turf (hydroid and bryozoan) assemblages and the composition of the wider epifaunal community. Each site had an “impact” box that was dredged, a control box that was in an area that was still open to fishing, and a control box in a special area of conservation (SAC) that had not been fished for two years. Community composition differed significantly after dredging in two of the three sites, with dredged communities becoming less similar to those in the SAC. There was no clear evidence that dredging in the impact boxes reduced the coverage of faunal turfs on hard substrates. However, the coverage of faunal turfs on hard substrates in the SAC was typically greater than in areas that were still being fished commercially, consistent with a dredging effect. The results highlight the role that substrate morphology might play in modifying the severity of dredging effects. This has relevance to marine spatial management, as it suggests that emergent epifauna living on hard substrates that are morphologically suited to dredging, such as pebble and cobble substrates, could be particularly vulnerable to dredging.

23 citations


Patent
10 Dec 2014

15 citations


Journal ArticleDOI
TL;DR: In this paper, the authors illustrate two examples of communication strategy adopted in the case of the dredging of the Port of Genoa (Italy) to ensure the correct data dissemination among the project partners and to the public.
Abstract: The stakeholders involved in a dredging operation are many and varied, some specifically involved in the technical aspects (client and dredging operators, organisations involved in legislative matters and/or environmental monitoring), and others less so (general public).These different kinds of stakeholders need different information and consequently different kind of data need to be produced (description of dredging objectives and scope, technical dredges characteristics, related legislation, environmental monitoring data, work progress, etc.) that need to be managed to share dredging information and knowledge. Here, we illustrate two examples of communication strategy adopted in the case of the dredging of the Port of Genoa (Italy) to ensure the correct data dissemination among the project partners and to the public. The first realized with a WebGIS (MArine Coastal Information SysTEm—Port Section, MACISTE-PS), a technology composed of data handling tools for storage, recovery, management and analysis of spatial data, and the second with a set of different communication products (posters, article publications, congress participations, website, etc.). The adoption of these two strategies assures us the dissemination of dredging information to a broad spectrum of people.


Journal ArticleDOI
TL;DR: An experimental study was conducted to characterize water masses, dynamics, and sedimentation rates on the Ligurian continental shelf (Italy), where both a sand deposit, that could be used for beach nourishment, and a nearby Posidonia oceanica meadow coexist.

Journal ArticleDOI
TL;DR: In this paper, a systematic procedure and maintenance plan for conducting dredging activity at the Kolkata port located in the Head Bay region, east coast of India is presented, which is one of the oldest riverine ports in the country constructed by the British East India Company.
Abstract: The present study reports on a systematic procedure and maintenance plan for conducting dredging activity at the Kolkata port located in the Head Bay region, east coast of India. It is one of the oldest riverine ports in the country constructed by the British East India Company. The port comprises two docks, viz. Kolkata Dock Complex and the Haldia Dock System under the administrative control of the Kolkata Port Trust. The navigation channel located in the Hooghly River accommodates sea-going vessels with 200 GRT with pilotage assistance cruising upstream almost 145 km from Sagar Islands located in Hooghly estuary. The navigation channel experiences high rates of sedimentation being a riverine port. This study investigates the sedimentation rate throughout the navigation channel, identifying zones of high sedimentation rate. The behavioural pattern of tides and currents is analysed using the state-of-the-art ADCIRC model, and wave conditions are simulated using SWAN model. The hydrodynamic information obtained from ADCIRC and SWAN is input to the SEDTRANS model. Based on the intensity of sedimentation, the maintenance plan is proposed for three dredging seasons. On the basis of this scientific rationale and seasonal dredging maintenance procedure, it is anticipated that huge investments involved in the maintenance dredging of this channel can be minimized.

Journal ArticleDOI
TL;DR: In this article, a spatially nested control-impact study of hydraulic dredging for bivalves, such as cockles (Cerastoderma edule), has been conducted.
Abstract: Hydraulic dredging for bivalves, such as cockles (Cerastoderma edule), has the potential to cause significant impacts on marine intertidal benthos. Although this fishing activity is common in northern European Natura 2000 sites such impacts may be incompatible with conservation objectives for designated habitats and species within these sites. In 2009–2010 a spatially nested control-impact study was undertaken before (t0), 8–9 days after (t1) and 4 months (t2) following dredging and extraction of 108 tonnes of cockles from a standing stock of 2158 tonnes in Dundalk Bay. This study failed to detect significant effects on benthic sediments, or the overall community structure. However, a fishing effect on the target species C. edule in one sampling area and a short lived effect on the bivalve Angulus tenuis were identified. Significant spatial and temporal variability in abundance of species and taxonomic groups, unrelated to fishing effects, was observed. Previous studies on the effects of fisheries on marine intertidal benthos have reported variable results, related to study design and objectives and the physical characteristics of the study site. Site specific studies, relative to the intensity and frequency of proposed fishing activity, may be required to adequately inform managers whether such activities are compatible with specific conservation objectives for Natura 2000 sites.

Journal ArticleDOI
TL;DR: A field trial was carried out to test the respective efficacy of three different mechanical dredge methods at reducing Corbicula clam numbers by estimating changes in abundance and biomass immediately following dredging as mentioned in this paper.
Abstract: The invasive Asian clam Corbicula fluminea (Muller, 1774) has established a high density and self-sustaining population within the tidal reaches of the River Barrow, Ireland. A field trial was carried out to test the respective efficacy of three different mechanical dredge methods at reducing Corbicula clam numbers by estimating changes in abundance and biomass immediately following dredging. Quadrat samples were collected by SCUBA divers before and after dredging. A maximum pre-dredge density of 17,872 individuals/m 2 and a biomass of 43.94 kg/m 2 was recorded. Three sites which supported different population density and biomass levels within the tidal section of the River Barrow were subject to each of the dredge methods. A reduction of greater than 95% biomass and 95% density was achieved at the high density, high biomass site, while an 82% biomass and 65% density reduction was recorded at the low density, low biomass site. A 74% biomass and 92% density reduction was achieved at the high density, low biomass site. The methodology and results indicate that, while dredging can achieve a large reduction in Corbicula population numbers, further research is required before this can be considered as a management tool for control of Asian clams.

Patent
27 Aug 2014
TL;DR: In this paper, a bottom sediment environment-friendly dredging system and a dredging method of the system is described. But the system comprises a ship and a sediment suction square box, a comprehensive control room, a ship position GPS position indicator, a positioning pile and a winch.
Abstract: Disclosed are a polluted bottom sediment environment-friendly dredging system and a dredging method of the system. The system comprises a ship and a sediment suction square box, a comprehensive control room, a ship position GPS position indicator, a positioning pile and a winch are arranged on the ship, and the winch is connected with the sediment suction square box through a cable rope. The sediment suction square box is connected with a sediment suction pump through a sediment suction pipeline. A bottom sediment GPS position indicator and a fathometer are arranged on one side of the sediment suction square box, an underwater illumination lamp and an underwater camera are arranged on the other side of the suction square box, a fluidizing device is arranged in the sediment suction square box, a sealing device is arranged at the bottom of the suction square box, and an exhaust pipe is arranged at the top of the sediment suction square box. A controller is arranged in the comprehensive control room on the ship. The dredging method of the system comprises the steps that the ship is in place, sediment suction is prepared, environment-friendly sediment suction is carried out, leaving is prepared, and the ship leaves. High-precision positioning of a dredged position and precise control over the dredging process are achieved, secondary pollution caused by sediment diffusion in the sediment taking process is avoided, dredging cost is effectively lowered, and dredging efficiency is effectively improved.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate a new screening method for risk assessment analysis in a scenario where economy, time and simplicity factors had been a concern The development of this method is based on a variation of standard ecological risk assessment An analysis will be performed on two elements Firstly, the level of contaminants in the water, groundwater and air (known as the media) and, secondly the behavior of environmental indicators during monitoring of historical dredging.
Abstract: Dredging in a contaminated river has been widely accepted to have an impact on the environment; however environmental risk assessment analysis could be costly, time-consuming and difficult to perform Therefore, a screening method acting as a preliminary risk assessment analysis to screen potential contaminated areas is necessary The aim of this study is to demonstrate a new screening method for risk assessment analysis in a scenario where economy, time and simplicity factors had been a concern The development of this method is based on a variation of standard Ecological Risk Assessment An analysis will be performed on two elements Firstly, the level of contaminants in the water, groundwater and air (known as the media) and, secondly the behavior of environmental indicators during monitoring of historical dredging This analysis is performed in order to establish the degree of contamination in an area that is about to be dredged, in where the publicly accessible contamination level in the media and the historical dredging monitoring data will be utilized Eight dredged sites in Peninsular Malaysia are selected as the case studies of this research This research showed that Sungai Perlis has a very high total risk value, which could have a fatal impact on its biodiversity if dredging is performed with negligence at this location This research could provide an opportunity for Malaysia to increase its efforts to avoid dredging impacts without being constrained on time, cost and simplicity factors

Journal ArticleDOI
TL;DR: This research proposed an executable precise dredging process, including sediment survey, model establishment, data interpolation, and calculation of dredging amount that would save 16 to 45 % of cost according to different pollutant removal demands.
Abstract: Environmental dredging is an efficient means to counteract the eutrophication of water bodies caused by endogenous release of nitrogen and/or phosphorus from polluted sediments. The huge operational cost and subsequent disposal cost of the dredged polluted sediments, as well as the adverse effect on the benthic environment caused by excessive dredging, make the currently adopted dredging methods unfavorable. Precise dredging, i.e., determining the dredging depth based on the pollution level, not only significantly decreases the costs but also leaves a uniform favorable environment for benthos. However, there is still no feasible process to make this promising method executable. Taking a river heavily polluted by organic compounds as an example, we proposed an executable precise dredging process, including sediment survey, model establishment, data interpolation, and calculation of dredging amount. Compared with the traditional dredging method, the precise one would save 16 to 45 % of cost according to different pollutant removal demands. This precise dredging method was adopted by the National Water Project of China to treat the endogenous pollution of Nanfei River in 2010. This research provides a universal scientific and engineering basis for sediment dredging projects.

Journal ArticleDOI
TL;DR: In this article, the concentrations of zinc, copper, cadmium, and lead in sediments of three different aquatic environments within an urban setting, a wetland, an estuary, and a marine harbor were determined.
Abstract: The objectives of our study were to (1) determine the concentrations of zinc, copper, cadmium, and lead in sediments of three different aquatic environments within an urban setting, a wetland, an estuary, and a marine harbor and (2) through a comparison of the concentrations and patterns of metal deposition among the three systems, assess both the historical and current sources of these trace metals to each of these environments. Such information is essential for the proper rehabilitation of these systems. To meet these objectives, we applied a three-dimensional mapping approach which allowed us to spatially visualize the extent of metal contamination within each of the urban aquatic environments. Such an approach proved useful in identifying the trace metal “depositional footprint” for each aquatic system. For the wetland, a creek which flowed into the wetland provided the primary source, for the estuary, the creek which fed the estuary, and a sewer outfall, and for the marine embayment, boat hull cleaning activities and two sewer outfalls were primary sources. Concentrations of metals ranged several orders of magnitude among the three aquatic systems; zinc, 2.5–709; copper, 7–3,667; lead, 4–698; and cadmium, 0.2–4.6 μg g−1 dry weight of sediment. The greatest range was for copper with the point source of copper-based antifouling paints contributing to the maximum concentrations determined for the three aquatic systems. All metals were significantly elevated in surficial sediments in all three ecosystems with recent accumulations of copper exceeding the probable effects level as recommended by the Canadian Council of Ministers of the Environment. It is most likely the primary source of this copper is from the abrasion of tires and brake pads. In the rehabilitation of these systems, attention will have to be paid to the dredging and proper disposal of sediments that have accumulated metals over time, especially those of copper that pose a toxicological concern to aquatic life. It is recommended that Canada as is being done in various jurisdictions in the USA as well as in Europe, pass legislation prohibiting the use of copper in brake pads.

Journal ArticleDOI
TL;DR: Hydraulicshellfish Harvesting conducted on leased shellfish bed in Long Island Sound did not appear to significantly impact benthic assemblages or sediment biogeochemistry, while sediment grain size and sampling date had a greater influence on benthics community structure.

Book ChapterDOI
01 Jan 2014
TL;DR: The most common approach for contaminated sediment remediation is the removal of contaminated sediments from the water body with subsequent treatment and/or disposal of the contaminated dredged sediment as discussed by the authors.
Abstract: Removal of contaminated sediments from the water body with subsequent treatment and/or disposal of the contaminated dredged sediment is the most common approach for contaminated sediment remediation. Various excavation equipment types and approaches have been used, including both dredging (excavation underwater) and excavation of the sediments in the dry. Excavation can be used as the sole active remediation approach or can be used in combination with monitored natural recovery (MNR) and/or capping. This chapter focuses primarily on environmental dredging as a contaminated sediment remedy component. The various treatment and disposal options available for contaminated sediments are also described in this chapter with a description of how they relate to the environmental dredging process, but these options are not covered in detail.

Journal ArticleDOI
TL;DR: In this paper, an examination for the dredging plan under process and two additional plans were performed using the Hydrologic Engineering Centers River Damage Analysis System software (HEC-RAS) for a 50 km long river reach to investigate whether they can recover the designed flooding capacity of the river or just improving it.
Abstract: River Tigris divides Baghdad, capital of Iraq, in two parts. The reach of the river within Baghdad is about 60 km long. Many islands and bars are obstructing the flow of the river within Baghdad. To overcome this problem, dredging operations started along most of Tigris River inside Baghdad City to remove many islands and side bars, which reduced the flooding capacity and the efficiency of water intakes. An examination for the dredging plan under process and two proposed additional plans was performed using the Hydrologic Engineering Centers River Analysis System software (HEC-RAS) for a 50 km long river reach to investigate whether they can recover the designed flooding capacity of the river or just improving it. Calibration and verification processes were implemented in the model using observed water levels at Sarai Baghdad gauging station and along the last 15 km of the river reach. Comparisons of computed water levels were conducted with those of previous studies and historical data. Some improvement of flood capacity was achieved based on the recorded data of the last three decades. Cautions about the water intakes should be considered to maintain their function with the expected drop in water level due to dredging operations.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the relationship between fish assemblage structure and pond management and via a comparative study before and after a dredging event, they found that the fish assembly structure was significantly different after the dredging events.

Journal ArticleDOI
TL;DR: In this article, a methodological procedure to estimate the environmental risk of dredging operations in aquatic systems has been developed based on numerical models results, which provide an appropriated spatio-temporal framework analysis to guarantee an effective decision making process.
Abstract: A methodological procedure to estimate the envi- ronmental risk of dredging operations in aquatic systems has been developed. Environmental risk estimations are based on numerical models results, which provide an appropriated spatio-temporal framework analysis to guarantee an effective decision-making process. The methodological procedure has been applied on a real dredging operation in the port of Marin (NW Spain). Results from Marin harbour confirmed the suit- ability of the developed methodology and the conceptual ap- proaches as a comprehensive and practical management tool.

Journal ArticleDOI
TL;DR: The IH-Dredge model simulates the evolution of the seabed, sediment and toxic substances involved in dredging operations and has been applied in a dredging operation in the Port of Marin, Spain.
Abstract: Historically, the study of dredging processes has depended on physical laboratory tests. The IH-Dredge model has been developed to simulate these processes numerically. It simulates the evolution of the seabed, sediment and toxic substances involved in dredging operations. The model has been calibrated and validated with experimental data, and it has been applied in a dredging operation in the Port of Marin, Spain.

Journal ArticleDOI
TL;DR: In this article, the authors introduce the problems associated with the dredging of sediment in the Polish coastal zone and point out no rules in Polish legislation in this regard, and develop a new legal aspects of Polish legislation containing the criteria for dredging material and principles for new locations of spoil dredging materials in the sea and of their monitoring.
Abstract: The aim of this work is introducing the problems associated with the dredging of sediment in the Polish coastal zone and pointing no rules in Polish legislation in this regard. A particularly pressing issue is to develop a new legal aspects of Polish legislation containing the criteria for dredging material and principles for new locations of spoil dredging material in the sea and of their monitoring. The authors also tend to develop the idea of the practical use of dredging sediments, including the criteria for artificial supplement the deficit of sediments of the coastal zone.

01 Jan 2014
TL;DR: In this paper, the authors investigated the impact of dredging on water quality of Dhamra estuary by evaluating the samples collected bi-monthly from various sampling stations during April-2008 to March-2010.
Abstract: Present investigation deals with the study of impact of dredging on water quality of Dhamra estuary, by evaluating the samples collected bi-monthly from various sampling stations during April-2008 to March-2010. Study revealed that the dredging operation has drastic impact on water quality of Dhamra, as total suspended solid and turbidity of both surface and bottom waters are high at dredging channel. Similarly, higher concentration of nutrients in dredging channel and disposal site shows clear impact of dredging. However, in certain points higher dissolved oxygen were observed in surface water at dredging channel may be due to higher phytoplankton production. But Biochemical Oxygen Demand of both surface and bottom water was intensely influenced by dredging due to release of organic rich sediment.

Journal ArticleDOI
TL;DR: Wang et al. as discussed by the authors analyzed the morphologic change caused by sand dredging in Poyang Lake basin by overlaying two DEMs acquired in 1952 and 2010 respectively, showing that the reflectance of middle infrared band for sand-diverging vessel is much higher than that of water surface, and can be counted in 12 Landsat images acquired in flooding season during 2000~2010.
Abstract: . Sand dredging has been practiced in rivers, lakes, harbours and coastal areas in recent years in China mostly because of demand from construction industry as building material. Sand dredging has disturbed aquatic ecosystems by affecting hydrological processes, increasing content of suspended sediments and reducing water clarity. Poyang Lake, connecting with Yangtze River in the lower reaches of the Yangtze River, is the largest fresh water lake in China. Sand dredging in Poyang Lake has been intensified since 2001 because such practice was banned in Yangtze River and profitable. In this study, the morphologic change caused by sand dredging in Poyang Lake basin was analysed by overlaying two DEMs acquired in 1952 and 2010 respectively. Since the reflectance of middle infrared band for sand dredging vessel is much higher than that of water surface, sand dredging vessels were showed as isolated grey points and can be counted in the middle infrared band in 12 Landsat images acquired in flooding season during 2000~2010. Another two Landsat images (with low water level before 2000 and after 2010) were used to evaluate the morphologic change by comparing inundation extent and shoreline shape. The following results was obtained: (1) vessels for sand dredging are mainly distributed in the north of Poyang Lake before 2007, but the dredging area was enlarged to the central region and even to Gan River; (2) sand dredging area reached to about 260.4 km2 and is mainly distributed in the north of Songmen Mountain and has been enlarged to central of Poyang Lake from the distribution of sand vessels since 2007. Sand dredged from Poyang Lake was about 1.99 × 109 m3 or 2448 Mt assuming sediment bulk density of 1.23 t m−3. It means that the magnitude of sand mining during 2001–2010 is almost ten times of sand depositions in Poyang Lake during 1955–2010; (3) Sand dredging in Poyang Lake has alternated the lake capacity and discharge section area, some of the watercourse in the northern channel was enlarged by more than 1 km when in low lake level. This study is useful to understand the change of hydrological system, especially the drying up trend in Poyang Lake in recent autumns and winters.

Patent
Ma Tao, Liu Yaqin, Liu Juan, Sun Fengkai, Gu Junjie 
22 Oct 2014
TL;DR: In this article, an environment-friendly dredging system for contaminated bottom sludge comprises a ship body and a square sludge sucking box, which is connected with a dredge pump through a sludge-sucking pipeline.
Abstract: The utility model provides an environment-friendly dredging system for contaminated bottom sludge. The environment-friendly dredging system for contaminated bottom sludge comprises a ship body and a square sludge sucking box. A comprehensive control room, a ship position GPS, a locating pile and a winch are arranged on the ship body. The winch is connected with the square sludge sucking box through a rope. The square sludge sucking box is connected with a dredge pump through a sludge sucking pipeline. A bottom sludge GPS and a fathometer are arranged on one side of the square sludge sucking box. An underwater lighting lamp and an underwater camera are arranged on the other side of the square sludge sucking box. A flow jetting device is arranged in the square sludge sucking box. A seal device is arranged at the bottom of the square sludge sucking box. An exhaust pipe is arranged on the top of the square mud sucking box. A controller is arranged in the comprehensive control room of the ship body. The dredging method of the environment-friendly dredging system comprises the steps of locating the ship body in place, making preparation for sludge suction, conducting environment-friendly sludge suction, making preparation for sailing away, sailing the ship body away and the like. By the adoption of the environment-friendly dredging system, high-precision locating of the dredging position and accurate control over the dredging process are achieved, secondary pollution caused by spreading of sludge during sludge suction is avoided, the dredging cost is effectively reduced, and the dredging efficiency is effectively improved.