Showing papers on "Dredging published in 2004"
TL;DR: In this article, a survey of benthic macrofauna in the vicinity of a coastal marine aggregate dredging site off the south coast of UK was carried out in 1999.
Abstract: A survey of benthic macrofauna in the vicinity of a coastal marine aggregate dredging site off the south coast of UK was carried out in 1999. The object of the survey was to determine impact of marine aggregate dredging on community composition, the extent of impact outside the boundaries of the dredge site, and the rate of recolonization and recovery of the fauna following cessation of dredging. Part of the site was intensively dredged by vessels at anchor whilst other parts were less intensively exploited by trailer dredger. The impact of dredging within the intensively exploited anchor dredge site was limited to the dredged area. Impacts included a suppression of species variety, population density and biomass, as well as differences in species composition compared with the surrounding deposits. In contrast, trailer dredging had no impact on community composition of macrofauna within the dredge site. No suppression of benthic community structure was recorded beyond 100 m from the dredge site. ...
90 citations
TL;DR: The U.S. Department of the Interior, Minerals Management Service, provides policy direction relative to the development of all marine mineral resources located beneath Federal waters of the United States as discussed by the authors.
Abstract: The U.S. Department of the Interior, Minerals Management Service, provides policy direction relative to the development of all marine mineral resources located beneath Federal waters of the United States. Over the last ten years or so, geological studies encompassing the collection and analysis of seismic, vibracore, and grain size data have been conducted in partnership with coastal States in the Atlantic and Gulf of Mexico to locate suitable sources of compatible sand for beach and coastal restoration. Environmental studies have been initiated to provide biological, physical, and other pertinent information for decisions regarding leasing and use of this resource. Aggregate dredging studies also have been conducted in the event that an offshore aggregate mining operation is proposed in the future. A symposium was held in New Orleans in January 2002 to report results from several studies completed over the past 2 years. The papers prepared for this Special Issue summarize the findings of recentl...
72 citations
TL;DR: In this paper, the authors show strong ramifications of dredging estuaries in other parts of the world, which are currently facing increased pressure from urbanisation and navigation requirements in conjunction with industrial developments.
Abstract: Extensive dredging in the Brisbane River estuary since European settlement has significantly altered estuarine hydrological and sediment transport processes. A large tidal ingress resulting from extensive dredging in the lower Brisbane River estuary and gravel extraction including point and non-point inputs in the upper estuary are currently maintaining two distinct turbidity maximum zones within the estuary: at the mouth (100–150 mg/L) and at about 60 km upstream (>300 mg/L). In addition, extensive dredging has also increased Brisbane estuary dry season flushing time significantly (>300 days) and as a consequence the estuary is currently unable to flush any point and non-point inputs beyond 35 km upstream from its mouth during the entire dry season resulting in a very high suspended sediment (SS) concentration all along the estuary except an area between two turbidity zones. In general, this work shows strong ramifications of dredging estuaries in other parts of the world, which are currently facing increased pressure from urbanisation and navigation requirements in conjunction with industrial developments.
68 citations
TL;DR: A detailed study of the seabed surrounding dredge pits created during the mining of marine aggregate from a small licence off the south coast of the United Kingdom (“Licence Area 122/3”) has been completed.
Abstract: A detailed study of the seabed surrounding dredge pits created during the mining of marine aggregate from a small licence off the south coast of the United Kingdom (“Licence Area 122/3”) has been completed. Over 350 km of high-resolution sidescan sonar imagery and 177 sediment samples have been obtained over a study area extending 10 km either side of the dredge zone (representing one full tidal excursion) in order to identify far-field effects on both physical and biological resources of the seabed. The physical results presented here for Area 122/3 clearly show that the physical impact of dredging (without screening) on the seabed is limited to a zone within approximately 300 m downtide of the dredge area. This will generally be within the dredge licence boundary due to operational procedures. There is no evidence of suspended sediments falling to the seabed beyond this zone and causing significant changes, which may be manifested as infilling of small pits by fine sediments, siltation within c...
53 citations
TL;DR: In this paper, the authors present a biological and physical monitoring program to evaluate long-term impacts from sand dredging operations in the United States Outer Continental Shelf (OCS) in order to reduce environmental damage associated with longterm and large-scale use of these resources.
Abstract: NAIRN, R.; JOHNSON, J.A.; HARDIN, D., and MICHEL, J., 2004. A biological and physical monitoring program to evaluate long-term impacts from sand dredging operations in the United States Outer Continental Shelf. Journal of Coastal Research, 20(1), 126‐137. West Palm Beach (Florida), ISSN 0749-0208. The Minerals Management Service (MMS) International Activities and Marine Minerals Division is charged with management of Federal Outer Continental Shelf (OCS) sand and gravel resources that would be used for beach nourishment to repair storm damage and protect against sea-level rise. To reduce environmental damage associated with long-term and large-scale use of these resources, a project was funded by MMS to design a comprehensive physical and biological monitoring program for sand-mining activities. An initial task of this project was performance of a literature review to determine where information gaps existed regarding the effects of sand mining and which physical processes and biological resources should be the focus of monitoring. Based upon the literature review and a conference with other investigators, the monitoring program was designed to include the following elements: benthic communities and their trophic relationships to fishes, marine mammals and wildlife (operational monitoring), sediment sampling and analysis, wave monitoring and modeling, bathymetric and substrate surveys, and shoreline monitoring and modeling. Protocols were developed for these elements to ensure consistency of methods among studies. The two primary physical impacts of concern are changes to the sea bed resulting in changes to the erosion and sedimentation processes along the shore and changes to the sea bed that would have a direct and significant impact on the biological environment. The most important biological impacts from dredging to be monitored in this program are changes in benthic secondary production and trophic transfer to fishes.
47 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
TL;DR: In this article, physical processes and biological data were collected and analyzed at five sand resource areas offshore Alabama to address environmental concerns raised by potential sand dredging for beach replenishment, with borrow site sand volumes ranging from 1.7 to 8.4 × 106 m3.
Abstract: Physical processes and biological data were collected and analyzed at five sand resource areas offshore Alabama to address environmental concerns raised by potential sand dredging for beach replenishment. Nearshore wave and sediment transport patterns were modeled for existing and post-dredging conditions, with borrow site sand volumes ranging from 1.7 to 8.4 × 106 m3. Wave transformation modeling indicated that minor changes will occur to wave fields under typical seasonal conditions and sand extraction scenarios. Localized seafloor changes at borrow sites are expected to result in negligible impacts to the prevailing wave climate at the coast. For all potential sand excavation alternatives at borrow sites offshore Alabama, maximum variation in annual littoral transport between existing conditions and post-dredging configurations was approximately 8 to 10%. In general, increases or decreases in longshore transport rates associated with sand mining at each resource area amounted to about 1 to 2% ...
34 citations
TL;DR: In this paper, a method is described for estimating both direct and indirect effects of dredging on shoreline change, where the direct effect results from infilling of the dredged pit via cross-shore sediment transport and is addressed statistically, assuming that the beach profile is in some arbitrary equilibrium shape.
Abstract: Nearshore dredging for construction aggregate or beach nourishment can result in a perturbation of natural littoral processes, changes in wave transformation patterns, and a net loss of sand from the littoral system. A method is described for estimating both direct and indirect effects of dredging on shoreline change. The direct effect results from infilling of the dredged pit via cross-shore sediment transport and is addressed statistically, assuming that the beach profile is in some arbitrary equilibrium shape. The indirect effect arises from project-induced wave transformation, which alters longshore sediment transport patterns, and is described using both spectral and monochromatic, numerical wave transformation models to provide input to a one-line model for shoreline change. Infilling of the pit is neglected when estimating the indirect effect, providing a worst-case estimate of the indirect effect. The methodology is applied to a site on the Turkish Black Sea coast, using hindcast wave data. The influences of pit location and geometry are investigated systematically, and recommendations regarding optimum pit dimensions and locations are made.
31 citations
TL;DR: The influence of former dredging activities along the river Leie on the alluvial plain quality was large and the pollution status of dredged sediment-derived soils was found to be far from negligible.
Abstract: The concept of an integrated multifunctional river management is gaining importance. For major rivers, restoring the contact between rivers and alluvial plains is an important goal, as riparian areas have a specific role for several riverine processes. However, former and current human activities are an obstruction or a limitation for river restoration. We studied the influence of former dredging activities along the river Leie on the alluvial plain quality. A soil survey and an archive query for reconstructing the history of dredging operations were conducted simultaneously. The geographical impact expressed as topographical changes and covering of the original soil profile and related processes and biota was large. The pollution status of dredged sediment-derived soils was found to be far from negligible: concentrations of Cd, Cr, and Zn were, in 10% of the cases, higher than 20, 480, and 2800 mg kg(-1) DM, respectively. Both agriculture and nature rehabilitation on dredged sediment-derived soils can only be accepted after profound risk assessment, and management should focus on ecological risk reduction. Results indicate the importance of soil quality assessment in alluvial plains for an integrated river management, rather than a priori assuming pristine soil conditions. The collected "off-line" sediment data can be used as a reconstruction of past sediment pollution, especially when long-term sediment monitoring programs are not available.
27 citations
TL;DR: In this article, the authors evaluated the differences in the output of various numerical models run with the natural and hypothetical post-dredging bottom conditions for the Fenwick and Isle of Wight Shoals offshore of the Delaware-Maryland border of the mid-Atlantic continental shelf.
Abstract: In an effort to assess the possible changes to physical oceanographic processes that might result from alteration of bathymetry as a result of dredging or sand mining, we evaluated the differences in the output of various numerical models run with the natural and hypothetical post-dredging bottom conditions. Fenwick and Isle of Wight Shoals offshore of the Delaware-Maryland border of the mid-Atlantic continental shelf served as the test site. We considered two dredging scenarios, a one-time removal of 2 × 106 m3 of sand from each of two shoals and a cumulative removal of 24.4 × 106 m3, but only the larger appeared significant. The study of wave transformation processes relied upon a series of runs of the REF/DIF-1 model using sixty wave conditions selected from analysis of the records from a nearby, offshore wave gauge. The model was tuned and calibrated by comparing measured near-shore wave conditions with data calculated using the same measured offshore waves that generated the real near-shore ...
25 citations
TL;DR: In this article, the impact of dredging on macrobenthic communities was studied in an unaltered zone, the Getares inlet of Algeciras Bay (SW Spain).
Abstract: The impact of dredging on macrobenthic communities was studied in an unaltered zone, the Getares inlet of Algeciras Bay (SW Spain). The data obtained before, during and after dredging in a time series spanning 5 years revealed the re-establishment of directly affected communities and of physicochemical substrate characteristics within 1 month of the end of dredging, although 2 years later there was a confusing biological impoverishment of the whole inlet. After 4 years, there was a high degree of population re-establishment, both on the bottoms directly affected by the works and on neighbouring areas, that was partly due to the hydrodynamic conditions. Before this type of activity is undertaken, each case should be studied regarding viability, the environmental medium where it will take place, the best time of year, and the type of dredging to be used.
TL;DR: A 34-year record of dredging in a 484-km reach of the Middle and Upper Mississippi River documents the spatial and temporal patterns of bed aggradation in an intensively engineered river as discussed by the authors.
01 Jan 2004-Journal of Environmental Science and Health Part A-toxic\/hazardous Substances & Environmental Engineering
TL;DR: High SOD-C values indicate that the sediment will cause a tremendous reduction in the oxygen concentration in a very short time at any marine environment, and even it may create anaerobic conditions, which makes the alternatives considering disposal in the Marmara Sea and Black Sea inapplicable.
Abstract: The Golden Horn has experienced severe pollution due to uncontrolled domestic and industrial wastewater discharges until recent years. A restoration project has been developed by our universities, upon a request from Istanbul Metropolitan Municipality. Two principal alternatives for the dredging and disposal of the bottom sediments were considered: disposing on the land and disposing in the sea. Both of these alternatives include several sub-alternatives. Characterization of the sediment quality is crucially important for selecting the best alternative considering the cost, environmental impact and public acceptance. However, only a few and rather old studies were present with which it was not possible to get a comprehensive information on the critical sediment characteristics. Therefore, the aim of this study was determination of spatial distribution of sediment characteristics. The project area, at which the sediment quality determined, covers the part of the Golden Horn remaining at the upstre...
TL;DR: The geo-environmental studies carried out to revitalise a silted up channel in Guanabara Bay evaluated the presence of heavy metals and organic compounds, particularly polycyclic aromatic hydrocarbons PAH and dredging and disposal schemes are briefly outlined.
TL;DR: A general, process-based dynamic model for coastal areas for radionuclides (metals, organics and nutrients) from both single pulse fallout and continuous deposition, which may be regarded as a tool for testing working hypotheses on the relative roles of different processes in different coastal areas.
01 Jan 2004
TL;DR: Newell et al. as discussed by the authors conducted a survey of benthic macrofauna in the vicinity of a coastal marine aggregate dredging site off the south coast of UK was carried out in 1999 to determine impact of marine aggregate mining on community composition, the extent of impact outside the boundaries of the dredge site, and the rate of recolonization and recovery of the fauna following cessation of dredging.
Abstract: NEWELL, R.C.; SEIDERER, L.J.; SIMPSON, N.M., and ROBINSON, J.E., 2004. Impacts of marine aggregate dredging on benthic macrofauna off the south coast of the United Kingdom. Journal of Coastal Research, 20(1), 115‐125. West Palm Beach (Florida), ISSN 0749-0208. A survey of benthic macrofauna in the vicinity of a coastal marine aggregate dredging site off the south coast of UK was carried out in 1999. The object of the survey was to determine impact of marine aggregate dredging on community composition, the extent of impact outside the boundaries of the dredge site, and the rate of recolonization and recovery of the fauna following cessation of dredging. Part of the site was intensively dredged by vessels at anchor whilst other parts were less intensively exploited by trailer dredger. The impact of dredging within the intensively exploited anchor dredge site was limited to the dredged area. Impacts included a suppression of species variety, population density and biomass, as well as differences in species composition compared with the surrounding deposits. In contrast, trailer dredging had no impact on community composition of macrofauna within the dredge site. No suppression of benthic community structure was recorded beyond 100 m from the dredge site. Species variety, population density, biomass and body size of macrofauna was enhanced for as much as 2 kilometers in each direction along the axis of the tidal streams. Whether this reflects organic enrichment derived from the dredge site warrants further investigation. The rate of restoration of biomass following dredging was slower than that recorded for species diversity and population density. The data for the North Nab study site allow a generalised recolonization sequence to be constructed for coastal deposits.
TL;DR: In this paper, a field investigation on sediment movement and beach evolution was performed in a fluvial system composed of the Samegawa River and the Nakoso coast, which experienced significant beach erosion recently.
Abstract: A field investigation on sediment movement and beach evolution was performed in a fluvial system composed of the Samegawa River and the Nakoso coast, which experienced significant beach erosion recently. Analyses of regional sand volume in the system revealed that the rate of decrease in nearshore sand on the beach is of the same order as the rate of accumulation of sand in dam reservoirs. Dredging of the riverbed near the river mouth also influenced nearby shoreline retreat. Long-term changes in sand movement processes were estimated from the distribution of mineral composition included in the sediment samples collected in a wide area.
01 Jan 2004-Journal of Environmental Science and Health Part A-toxic\/hazardous Substances & Environmental Engineering
TL;DR: A two-dimensional analytical transport model is developed to predict the dredge induced plume concentration in the horizontal plane under steady-state for simple hydraulic conditions and provides the ability to account for the rapid settling of larger particles in the suspended sediment near the dredging operations while simulating the slower settling and diffusive transport of smaller particles moving away from the drediting sites.
Abstract: A two-dimensional analytical transport model is developed to predict the dredge induced plume concentration in the horizontal plane under steady-state for simple hydraulic conditions. The derivation of the analytical solution is based on the solution to the advection-diffusion equation. The application of this analytical model is limited to mechanical dredge operations, bucket dredge, which has continuous point source in the water column. The analytical model developed herein is used to simulate sediment concentration distributions from a hypothetical dredging site and compared to results from a similar model using Stokes' settling. The result shows that Stokes' settling underestimates settling in the near-field and overestimates settling in the far-field plume. In summary, the model provides the ability to account for the rapid settling of larger particles in the suspended sediment near the dredging operations while simulating the slower settling and diffusive transport of smaller particles moving away from the dredging sites.
TL;DR: Throughout the project area the mussel fauna exhibited little or no evidence of recent recruitment, dominance of relatively few species, and low species diversity (H') and evenness, and maintenance plans were redesigned to minimize environmental damage.
01 Jan 2004
01 Jan 2004
TL;DR: Wang et al. as mentioned in this paper 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.
TL;DR: The water quality assessment software developed herein will greatly enhance the ability of the predictive tool for estimating sediment transport and resuspension during dredging operations.
Abstract: A Web-based dredge plume simulation software has been developed for estimating sediment transport and contaminant release from dredging operations. This application software comprises a near-field source model and far-field sediment transport model, combined with the settling analysis of flocculent particles. It is designed to run on all computing platforms with a standard Web browser and is accessible over the Internet. This paper describes its internal software structures and the major features of the application software. In addition, an example application of sediment transport in the Savannah River, GA, is included to illustrate typical input and output screens and to demonstrate the accuracy of the model. The water quality assessment software developed herein will greatly enhance the ability of the predictive tool for estimating sediment transport and resuspension during dredging operations.
Patent•
18 Feb 2004
TL;DR: A technology for building artificial land includes pumping the sludge generated by dredging the navigation channel or harbour in mixing pool, adding coagulant, stirring, pumping in deposition pool, depositing, removing water layer, and naturally drying the earth layer for 2-3 years as discussed by the authors.
Abstract: A technology for building artificial land includes pumping the sludge generated by dredging the navigation channel or harbour in mixing pool, adding coagulant, stirring, pumping in deposition pool, depositing, removing water layer, and naturally drying the earth layer for 2-3 years.
Journal Article•
TL;DR: The sediment dredging was conducted for decreasing the pollution load and controlling the eutrophication in Xuanwu Lake in 1998 as discussed by the authors, and the monitoring results of total nitrogen (TN), total phosphorus (TP) and heavy metals in sediment were used to assess the effect of the dredging.
Abstract: The sediment dredging was conducted for decreasing the pollution load and controlling the eutrophication in Xuanwu Lake in 1998. The monitoring results of total nitrogen (TN), total phosphorus (TP) and heavy metals in sediment were used to assess the effect of the dredging. Compared with 1998, TP content of the sediment decreased slightly in 1999, but increased in 2000. A continuous increase of TN content in sediment took place after dredging. At the same time, the pollution loading of heavy metals, such as Hg, Cu, Pb, Cd, Cr, has been rising since 1998. Especially, in 2000 Hg content in Northwestern part of Xuanwu Lake was 36 times as much as that in 1997 (before dredging).
15 Jan 2004
TL;DR: In this paper, a modified dredge impact model was developed using the data collected in this study, which should estimate crab adult equivalent loss and associated error rates to gain a population-level perspective on the potential entrainment impacts at each of the three alternative sump areas.
Abstract: The Portland District of the U.S. Army Corps of Engineers is investigating plans to provide sediment to nourish beaches north of the Mouth of the Columbia River (MCR). Under the currently designed proposal, sediment dredged from the MCR will be temporarily stored at one of three proposed areas south of the North Jetty before being redredged and moved by a cutterhead pipeline dredge over the jetty to nourish Benson Beach. Resulting potential impacts to resident Dungeness crab (Cancer magister) and fishes represent one of the criteria for evaluating each of the alternative locations. To establish the species composition and relative abundance of crabs and fishes associated with each of the three proposed sump areas, researchers from the Pacific Northwest National Laboratory Marine Sciences Division completed nine field sampling trips from July 8, 2003, to November 1, 2003, for a total of 113 successful trawls comprising an area of over 7.4 ha (74,156 m2). This report documents the results of that effort. To understand the relative risk of losses to crab populations associated with dredging impacts at the sump alternative areas, it is recommended that a modified dredge impact model be developed using the data collected in this study. This modelmore » should estimate crab adult equivalent loss and associated error rates to gain a population-level perspective on the potential entrainment impacts at each of the three alternative sump areas. As well, a sustained survey of Dungeness crab distribution and movement within the Columbia River estuary would clarify the relative value of the sump areas as a migratory corridor for crab populations, and support management decisions relative to issues associated with dredged material handling and disposal.« less
01 Jan 2004
TL;DR: In this article, the authors developed a dredging index by combining four numerical sets of sediment quality judgement into a quadrodiagram for prudential decisions, which was applied to the data obtained from Masan Bay before and after the dredging process.
Abstract: There is a need to have a dredging index for decision of contaminated sediments dredging. Some differences from nation to nation were found in sediment quality guideline being applied by several nations because of economic level, environmental nature, and multiple uses. Therefore, it is not reasonable to adapt one guideline to be applied to sediments dredging. In this study, we developed dredging index by combining four numerical sets of sediment quality judgement into a quadrodiagram for prudential decisions. This newly developed dredging index was applied to the data obtained from Masan Bay before and after the dredging process. The quadrodiagrams of DI give us a nice graphical comparison and numerical values to explain the relative dredging effect under the circumstances of continuous input loadings. When the guideline value of DI is determined for the judgement of dredging considering social and economic impacts on local community, the DI value will be a scientific and reasonable tool in deciding dredging area and dredging depth.
01 Jan 2004
TL;DR: In this paper, the impact from silting and sedimentation of sediment spill is very local due to the low content of fines in the resource, and that the impact on valuable habitats outside the dredging area is insignificant.
Abstract: In the Danish part of the western Baltic Sea, marine aggregates can roughly be classified into basic geological settings suitable for sand fill for land reclamation, and sand, fine gravel and coarse gravel for construction purposes, primarily as aggregate for concrete. In addition to this, some sand and gravel products possess unique qualities making them suitable for special purposes such as moulding sand. Taking natural and administrative restrictions into account, marine aggregates are dredged at a number of designated locations in coastal waters, and in open waters where dredging takes place in the Adler Ground - ROnne Bank area. Total annual extraction in the region is 1.5 to 2 million m 3 , depending on local and international demand. Based on geological surveys, including seismic, surface sampling and coring, the late glacial and Holocene history of the Ronne Bank-Adler Ground is described, and an example of habitat identification and impact assessment is illustrated. More than 1.5 billion m 3 of sand and gravel are located in different resource areas on the Ronne Bank and Adler Ground, which probably makes it the largest known resource in the Baltic. The sand fraction on the Ronne Bank is generally of high quality suitable for the production of high class concrete. Also the coarse aggregates are of high quality and large amounts have been exported to Germany over the years. Based on sediment distribution, a number of habitats have been identified and mapped according to the EU-Habitat Directive. Examples of hydrographical settings and content of fines in the resource have been used to model the environmental impact from sediment spreading during aggregate dredging in the area. The results show that the impact from silting and sedimentation of sediment spill is very local due to the low content of fines in the resource, and that the impact on valuable habitats outside the dredging area is insignificant.
01 Jan 2004
TL;DR: Sediment characteristics and bottom fauna were investigated extensively in and around Cochin harbour at 38 sampling stations grouped into seven areas, covering an area of 130 km, during premonsoon and monsoon periods as mentioned in this paper.
Abstract: Sediment characteristics and bottom fauna were investigated extensively in and around Cochin harbour at 38 sampling stations grouped into seven areas, covering an area of 130 km, during premonsoon and monsoon periods. The seven areas were: (I) Ernakulam channel (4-10 m deep). (2) Mattanchery channel (2.5-5.5 m deep). (3) Vallarpadam (2.1-4.5 m deep). (4) Dredging channel (8.5-17.0 m deep). (5) North of dredging channel (6.6-14.0 m deep). (6) South of dredging channel (6 6-14.0 m deep) and (7) Disposal site (12.8-17.5 m deep). The silty clay and sandy clay substratum predominated the study area. In the dredging and disposal areas the values for organic matter were 3.40 and 4.51% during pre-monsoon and 3.51 and 4.00% during monsoon respectively. The standing stock in terms of total biomass (wet weight) in the study area varied from 37.47 to 297.30 g m' during premonsoon and 12.63 to 215.97 g m during monsoon. The distribution of different faunal groups/species indicated a significant reduction in the dredging and disposal areas Polychaetes dominated the fauna. Bray-Curtis. Coefficient of Similarity between areas was higher during monsoon than during premonsoon in areas 4-6 with sediment characteristics controlling the occurrence of common species. Species which are highly abundant and more homogeneously distributed have low niche breadth preferably in sand dominated areas, particularly in areas 1 -4. In area 5, a similar trend was observed with high niche breadth associated with organic matter content, whereas in areas 6 and 7 a reverse in the trend was observed with finer sediment dwelling organisms showing high niche breadth. In general a decreasing trend in the species niche breadth was observed from area I to 7 with higher values during monsoon than during premonsoon for species niche breadth. Grouping of species obtained by group average linkage clustering and using R-mode analysis are compared:
01 Jan 2004
TL;DR: In this paper, the granulometric facies can be described quantitatively based on a large data set covering the entire western Baltic by a 1 x 1 nm sampling grid, and generalized parameters are used describing the grain size distributions of samples taken during fifty years of sedimentological investigations in the western Baltic Sea.
Abstract: Sand and gravel deposits in the western Baltic Sea have formed mainly as a result of postglacial erosion processes, selective transport and re-deposition of glacial sediments. The regional distribution of various types of deposit reflects the geological setting (regional pattern of glacial moraines) as well as the hydrographic environment responsible for near-bottom transport and deposition. The granulometric facies can be described quantitatively based on a large data set covering the entire western Baltic by a 1 x 1 nm sampling grid. For facies regionalisation, generalized parameters are used describing the grain size distributions of samples taken during fifty years of sedimentological investigations in the western Baltic Sea. A comparison with results from hydrographic modelling explains natural sediment transport pathways from the sources (coastal areas and sills) to the depocenters (basins). Shallow seismic lines and sediment cores provide the data needed for resource mass balancing. Based on those data sets, a total of 11000 000 m 3 gravel, and 14500000 m 3 sand have been proven in the last three decades. Thirty one percent of the deposits have been exploited and used as raw material for the construction industry. The major part of the deposits (69 %) form reserves for coastal protection of the Baltic Sea coast. Whereas the demand for psammitic sediments for the construction industry has been decreasing continuously since 1997, coastal protection plans have held the demand for sand for refilling eroded parts of sinking coastal areas within the German State of Mecklenburg-Vorpommern fairly stable since 1998. The expected demand for offshore sand and gravel during the next decade is covered by already proven resources. International and national laws and regulations have resulted in a balance between the supply of mineral resources exploited by offshore dredging and the protection and conservation of marine ecosystems.
01 Jul 2004
TL;DR: A more structured approach to conducting research into the generation and impact of sediment released by dredging was proposed at a meeting held in Washington DC in January 2003 as mentioned in this paper, including US Army Corps of Engineers (USACE) and Environmental Protection Agency (EPA).
Abstract: At a meeting held in Washington DC in January 2003 a number of organisations in the USA, including US Army Corps of Engineers (USACE) and Environmental Protection Agency (EPA), and Europe recognised the need for a more structured approach to conducting research into the generation and impact of sediment released by dredging. The authors were commissioned to produce a framework for research and presented some of the preliminary findings at WEDA XXIII.