The system records in-situ water quality data at a depth of 26 feet, including temperature, salinity, turbidity, backscatter, PAR (Photosynthetically Active Radiation), and currents, among other parameters. Additionally, climate data is collected at the surface, which includes wind, pressure, and PAR. This data is continuously gathered from a buoy located in Port Everglades, Florida, covering both the sea surface and the seafloor. The bottom-deployed sensor array is equipped with an Echologger ECT400 altimeter, Aqua TROLL 600 (In Situ), acoustic modem, NexSens data logger, Nortek wave/current meter, an ECO-PAR sensor that measures photosynthetically active radiation–specifically the light levels crucial for photosynthesis, and LISST-ABS acoustic sediment sensor to continuously monitor sediment dynamics. Data collected by the bottom array is logged by a NexSens logger, and then an acoustic modem transfers the data through the water column to the CB-950 data buoy on the surface that is equipped with another NexSens logger and an Airmar multiparameter weather station and LI-COR PAR sensor to measure climate conditions. Data from the surface buoy and the bottom sensor package are transferred to the cloud, where the data can be viewed via WQData LIVE.

NOAA's ENC Direct to GIS web portal provides comprehensive access to display, query, and download all available NOAA ENC data in a variety of GIS/CAD formats for non-navigational purposes using Internet mapping service technology. An area of the bottom of a body of water which has been deepened by dredging.(IHO Dictionary, S-32, 5th Edition, 1462)

Data is in the form of a Microsoft Access databases, excel workbooks and csv files, showing the original data together with site information (GPS coordinates), and date collected. Data is also in the form of a report, which will be a secured (printable, non-editable), searchable, Portable Document Format (PDF) showing the results of the analyses.

Dredge plumes are formed when dredging operations suspend rock and soil particles into the water column by mechanical, scouring and mixing actions and by direct discharges from dredging equipment. The size composition and settling velocity distribution of these suspended particles depends on the in situ characteristics of the material to be dredged and on the changes to the material which occur as it is worked by the dredging equipment.

Estimation of the far-field suspended sediment source terms is a challenging task, particularly at the EIA stage of the dredging project proposal, given project design, engineering and geotechnical uncertainties at that stage. The two basic approaches used are: • empirical - using source term estimates previously derived from on board and dredge plume data sets collected under circumstances and conditions similar to those anticipated for the current dredging proposal • process-based - using calibrated and validated numerical models based on an understanding of the physical processes and input data that determine the far-field source terms.

The environmental impact assessment (EIA) documentation associated with 15 dredging projects in Australia (12 from WA) were reviewed to examine the practices used to estimate suspended sediment source terms for input into far-field dredge plume prediction models. The review focused on the key source term contributions from CSD and TSHD dredgers.

The reviews highlighted the importance of dredge-induced sediment suspension datasets being collected according to agreed protocols and methods so that source term calculations from these data sets can be reliably ranked and compared. Overall, the number of these datasets has increased significantly in recent years. However many of these are not publicly available and their availability (and potential use) is restricted. Also, there are some relatively common dredging situations (e.g. trailing suction hopper dredging with low under keel clearance) that are not well represented by the available datasets. The acquisition of high quality datasets, from both full-scale dredging operations and laboratory experiments, also leads to an improved understanding of the physical processes involved in the generation and release of dredged material particles and the early stages of plume formation. This enables the development of process-based source models as an additional means of estimating source terms. It was not possible to recommend numerical values for source term parameters to use under local conditions based on these reviews, due to the paucity of relevant field data against which to compare estimates.

A number of recommendations were made to address this, including:

• adoption of standard protocols for field data collection to evaluate source terms during project implementation stage;

• establishment of a dredge source term data library that could be populated over time, to cover the different types of dredges used and the various geotechnical conditions encountered in capital dredging practice in Australia; • adoption of a consistent, transparent accounting method (Becker et al. 2015, van Eekelen 2015) for reporting source term estimates for dredge plume modelling as part of EIA.

The objective of WAMSI DREDGING SCIENCE NODE Project 4.3 was to better understand the relationship between TSS and the orbital motion of waves using the instrumentation used during the Gorgon dredging program, at multiple sites using the baseline (pre-dredging) data and then during the dredging program. Specifically, the objective was to predict TSS levels based on the orbital velocity of waves and to identify periods where the measured TSS levels are higher than the modelled data predicts and which therefore may indicate turbidity caused by dredging or spoil disposal and which could represent periods of high sediment deposition. The information from the sediment deposition sensor can then be used to verify periods of high(er) sediment deposition..


Data is in the form of a report, which is a secured (printable, non-editable), searchable, Portable Document Format (PDF) showing the results of the analyses.

Link to the ScienceBase Item Summary page for the item described by this metadata record. Service Protocol: Link to the ScienceBase Item Summary page for the item described by this metadata record. Application Profile: Web Browser. Link Function: information

The four adjacent Outer Cape communities of Eastham, Truro, Provincetown, and Wellfleet have built an intermunicipal partnership to pursue a regional approach to shoreline management. This partnership promotes short- and long-term science-based decisions that will maximize the effectiveness and efficiency of community responses to the increased threat of coastal hazards. This layer is a product of that partnership, the Intermunicipal Shoreline Management Project, a project first initiated in 2019 with funding from CZM's Coastal Resilience Grant Program.Average annual sediment deposition rates were calculated for those areas of Pamet, Wellfleet, and Rock Harbors routinely dredged for navigation purposes. Calculation of the annual sedimentation rate was based on the total area of the dredge footprint; the historical record documenting when the harbors were dredged, and the amount of material removed. Since this rate can vary over time in response to changing environmental conditions such as rising sea levels, the number and intensity of coastal storms, and reductions in sediment sources due to coastal armoring, the data product has been provided as a potential planning metric to be developed further in the future as more dredging data becomes available. As a gross measure of the rate at which a harbor is experiencing deposition, the average annual sedimentation rate was calculated to explore it’s viability as a rule-of-thumb for estimating the frequency at which Pamet, Wellfleet, and Rock Harbors need to be dredged in order to maintain desired channel depths. The calculated rates are intended to be used as a rule-of-thumb for planning purposes only and not for calculating actual dredge volumes or payment amountsAverage annual sediment deposition rates (AASR) in vertical feet per year were estimated for Pamet, Wellfleet, and Rock Harbors as follows: AASR = ((Dvol / Time) x 27) / DareaDvol = Total volume of dredged material (cubic yards) from all yearsTime = Length of dredging record used (years)Darea = Area of dredge footprint (square feet)Last updated Nov 2022

Federal navigation projects were inventoried to determine the extent to which Regional Sediment Management (RSM) goals and beneficial use of dredged material have been implemented across the USACE Districts at the project, District, and Division levels. Data from the USACE Institute for Water Resources (IWR) Navigation Data Center’s Dredging Information System (DIS) were utilized and considerably refined using District managed information and data. A web-application, a District Specific/Quality Checked (QC) database, and a database of USACE DIS data specific to this project were produced.

Eutrophication of freshwater ecosystems is a major global problem, but restoration can be difficult due to ongoing problems relating to water pollution, sedimentary nutrient stores, and altered aquatic biodiversity. Mitigation of water quality stressors is often conducted alongside transplantation of submerged macrophytes and dredging, but knowledge of ecosystem response to post-dredging transplantation of submerged macrophytes is limited. Here, we report a long-term (2008-2018) in-situ monitoring study to evaluate the effects of two different restoration measures: dredging only (Dredged) and dredging with post-dredging transplantation of submerged macrophytes (Dredged with macrophytes) conducted in five subtropical eutrophic lakes in Lake Taihu basin, China. Water and sediment nutrients, bloom-forming algae Microcystis, and macroinvertebrate were monitored every two years for each treatment and compared with reference areas (Control) established in unrestored parts of the same lakes. Dredging only decreased sediment nutrients (nitrogen, phosphorus, total carbon, and water total phosphorus significantly, however, this effect diminished about five years later. Dredged with macrophytes had a stronger, longer-lasting positive effect on water quality than Dredged alone. Disturbance caused by dredging (without macrophytes transplantation) decreased the biomass of Microcystis, while transplantation of submerged macrophytes shortly after dredging did not contribute to the decrease of Microcystis biomass. The biomass of Microcystis in Dredged with macrophytes areas was always similar to Control over the period of our monitoring. A positive effect of submerged macrophytes transplantation post-dredging was found for macroinvertebrate abundance and diversity: Dredged with macrophytes areas had significantly higher macroinvertebrate biomass and richness than Dredged areas after 9 years’ recovery. Macroinvertebrate richness in Dredged with macrophytes areas nearly doubled compared to Control; while Dredged areas were just restored to Control levels. Synthesis and applications. Our study provides an in-situ long-term field monitoring with new findings about the benefits and caution of submerged macrophytes transplantation post-dredging, and the effect of partial restoration, which could inform eutrophic waterbody restoration schemes.

Global Dredging market size earned around $17.86 Billion in 2023 and is expected to reach $22.30 Billion by 2032, with a projected CAGR of 2.5%.

This web-based application was created by BCDC to support the Long Term Management Strategy for the Placement of Dredged Material in the San Francisco Bay Region (LTMS) program and the National Marine Fisheries Service’s 2011 LTMS Programmatic Essential Fish Habitat (EFH) consultation. The web application can assist project planners in identifying potential impacts of dredging projects in San Francisco Bay to eelgrass based on the LTMS EFH consultation. Once inside the application, click on the “about” button to learn more about assessing impacts and make sure to refer to the EFH consultation linked above for more specific information. Layers in this application include: 1) the maximum extent of eelgrass beds that have been surveyed in San Francisco Bay shown in green; 2) a 45-meter growth buffer for potential bed expansion shown in blue; 3) Polygons demonstrating where dredging occurs within San Francisco Bay; and 4) a 250-meter turbidity buffer around dredging footprints. The eelgrass survey data used in this web application represents the best available data on comprehensive eelgrass extent throughout San Francisco Bay as of 2021. The original eelgrass survey data were developed by Merkel & Associates, Inc. (Merkel) using a combination of acoustic and aerial surveys and site-specific ground truthing. This web application may be used to determine potential direct and indirect impacts to eelgrass habitat from dredging projects as described in the LTMS EFH consultation. These data do not replace the need for site-specific eelgrass surveys as directed by the regulatory and resource agencies.Data from the 2003, 2009, and 2014 baywide eelgrass surveys and associated Merkel reports, which include information on mapping methodology, are available for download on the San Francisco Estuary Institute’s (SFEI) website. Data from a Richardson Bay survey conducted by Merkel in 2019 is also included in this application. For further information on methods used here please enter the application by clicking “View Application” on the right, then click the “…” next to each layer, and then select “Show item details" in the drop-down menu for each individual layer.

Dredge sampling was carried out aboard the James Clark Ross (cruise no JR77 ) during Feb and Mar 2004. The dredge target area was along the eastern segments of the West Scotia Ridge, an ocean spreading centre which stopped spreading about 10 million years ago. The spreading centre has high topographic relief and contains an axial rift, which has flanks that are suitable for dredging. The plan was to map the spreading centre using the swath bathymetry system, and then to use this map to locate the best dredging sites. Thirteen dredges were successful in recovering oceanic rocks of mixed sizes, up to and including very large boulders and dredge paths of up to 1 km were followed.

Coastal development is contributing to ongoing declines of ecosystems globally. Consequently, understanding the risks posed to these systems, and how they respond to successive disturbances, is paramount for their improved management. We study the cumulative impacts of maintenance dredging on seagrass ecosystems as a canonical example. Maintenance dredging causes disturbances lasting weeks to months, often repeated at yearly intervals. We present a risk-based modelling framework for time varying complex systems centred around a dynamic Bayesian network (DBN). Our approach estimates the impact of a hazard on a system's response in terms of resistance, recovery and persistence, commonly used to characterise the resilience of a system. We consider whole-of-system interactions including light reduction due to dredging (the hazard), the duration, frequency and start time of dredging, and ecosystem characteristics such as the life-history traits expressed by genera and local environmental conditions. The impact on resilience of dredging disturbances is evaluated using a validated seagrass ecosystem DBN for meadows of the genera Amphibolis (Jurien Bay, WA, Australia), Halophila (Hay Point, Qld, Australia) and Zostera (Gladstone, Qld, Australia). Although impacts varied by combinations of dredging parameters and the seagrass meadows being studied, in general, 3 months of duration or more, or repeat dredging every 3 or more years, were key thresholds beyond which resilience can be compromised. Additionally, managing light reduction to less than 50% can significantly decrease one or more of loss, recovery time and risk of local extinction, especially in the presence of cumulative stressors. Synthesis and applications. Our risk-based approach enables managers to develop thresholds by predicting the impact of different configurations of anthropogenic disturbances being managed. Many real-world maintenance dredging requirements fall within these parameters, and our results show that such dredging can be successfully managed to maintain healthy seagrass meadows in the absence of other disturbances. We evaluated opportunities for risk mitigation using time windows; periods during which the impact of dredging stress did not impair resilience.

Percent dredged canal density and wetland loss in Louisiana https://doi.org/10.5061/dryad.sn02v6x9s The dose-response relationships between the percent dredged canals and percent land loss in Louisiana and Nigeria coastal zone were quantified using land and water data. Published data in 7.5' and 15' quadrangle maps for the Louisiana deltaic coastal zone from 1932 to 1990 are included in this data file as well as some unpublished data records. The %land loss relative to the baseline land area at the start of the interval was calculated. A direct relationship between dredged area and land to water conversion is demonstrated that accelerates over decades. ## Description of the data and file structure The data are in an excel spreadsheet accompanied by location maps for the Louisiana coast. The units for the area of land and water are 'acres' (the original reporting units). The percent land or percent canal in maps of different dates are in %. * Worksheet Baseline Numbering: The base map identification numbering is given that is common to all data sets from 7.5' and 15' quadrangle maps of the Louisiana coast. * Worksheet Britsch and Dunbar 1993: The data from these authors are for map in the early 1930s, 1958, 1974, 1983 and 1990. The worksheet includes the area of canal and land in 15' quadrangle maps, and the calculated % canal and land in each quadrangle map. The Quadrangle number is the base map number identified in the Worksheet 'Baseline Numbering' * Worksheet Scaife et al. 1983: These are data that Scaife et al. (1983) used to measure the relationship between % land loss from 1955 to 1978 and the canal density relative to that existing in 1958 in 7.5 minute quadrangle maps for St. Breton Sound, Barataria and Terrebonne Parishes. The Quadrangle number is the base map number identified in the Worksheet 'Baseline Numbering' * Worksheet Turner and Rao 1990: These are data that Turner and Rao (1980) developed when studying the relationship between pond size and distance from canals in Terrebonne and Barataria Parishes, but did not report in the journal article. Maps identified as 'near' or 'far' maps include a portion of the Mississippi River or not, respectively.The Quadrangle number is the base map number identified in the Worksheet 'Baseline Numbering' * Worksheet Bass and Turner 1997: These are data that Bass and Turner (1997) used to quantify the relationship between the % canal in 1990 of land in 1956 and the land loss from 1956 to 1990. Ninety nine percent of the land was wetland. The sites were in Terrebonne, Barataria and St. Bernard Parishes. The Site number refers to the number in the original paper by Bass and Turner (1997). ## Sharing/Access information This is a section for linking to other ways to access the data, and for linking to sources the data is derived from, if any. none Data was derived from the following sources: Bass, A. & Turner, R. E. Relationships between salt marsh loss and dredged canals in three south Louisiana estuaries. J. Coastal Res. 13, 895-903 (1997). Britsch, L. D. & Dunbar, J. B. Land loss rates: Louisiana coastal plain. J. Coastal Res. 9, 324–338 (1993). Scaife, W. W., Turner, R. E. & Costanza, R. Coastal Louisiana recent land loss and canal impacts. Environ. Managmt. 7, 433–442 (1983). Unpublished data acquired from the Corps of Engineers, New Orleans District, LA is merged with this data. Turner, R. E. & Rao, Y. W. Relationships between wetland fragmentation and recent hydrologic changes in a deltaic coast. Estuaries 13, 272-281 (1990). ## Code/Software no codes Excel software The direct effects of converting wetlands to open water by dredging can be magnified by indirect effects. For example, the dredged canal allows for recovery of mineral fluids 1000s of m belowground which may induce geological subsidence or faulting; dredged material deposited at the surface to form continuous levees may create hydrologic stressors on the wetland plants resulting in a conversion to open water habitat as a result of both soil waterlogging and drying, less organic matter and sediment accumulation, or greater erosion. We quantified indirect effects by demonstrating a robust dose-response relationship between coastal land loss and dredging canals in the Mississippi and Niger river deltas over 60 years. Importantly, the ratio of land loss to canal area increases with time – a legacy effect. We also found that flood protection levees on the main channel did not magnify the effect of dredging on wetland loss by inhibiting sediment flow into adjacent wetlands along its banks. Published and unpublished data are reported for digitized areas of land and canal for 15' and 7.5' maps in the Louisiana coastal zone. No transformations of the data were done.

This is data collected during dredging by the Townsville Port Authority in Cleveland Bay in 1993. Data are divided into a number of main groups: Wind, tide gauge, wave rider, S4, sediment traps, water samples and nephelometers.

Unique site numbers were assigned within Cleveland Bay at which data were collected. Some of these sites were named, and others were unnamed.

Analysis of ‘LIS Dredged Material Disposal Sites’ provided by Analyst-2 (analyst-2.ai), based on source dataset retrieved from https://catalog.data.gov/dataset/7fd4cda6-6db6-46e3-85f1-0462666af6dd on 27 January 2022.

--- Dataset description provided by original source is as follows ---

LIS Dredged Material Disposal Sites is a polygon feature-based layer that depicts the official locations of the four active (currently used) sites for depositing sediments approved for open water disposal in Long Island Sound. It does not include historic or discontinued disposal sites. The layer was compiled initially between 1999 and 2001 and depicts current conditions. Compilation scale is unknown. Attribute information is comprised of codes to uniquely identify individual features (locations of dredge disposal sites), encode the features, and cartographically represent (symbolize) these features on a map. This layer is updated as needed. Disposal activities in Long Island Sound are regulated by the following Federal statutes: the Clean Water Acts of 1977, the Coastal Zone Management Act, the Endangered Species Act of 1973, the Marine Protection, Research, and Sanctuaries Act of 1972, the National Environmental Policy Act of 1969, the Fish and Wildlife Coordination Act of 1958, and the Rivers and Harbors Act of 1899. In addition to Federal oversight, both Connecticut and New York also regulate open water disposal in the waters of Long Island Sound. In Connecticut, authority stems from the state's Structures, Dredging and Fill statute, the Tidal Wetlands statute, and the Connecticut Coastal Management Act. In New York, disposal is regulated through the Use and Protection of Waters Regulation, the Tidal Wetlands Use Regulations, the Coastal Erosion Management Regulations, the State Environmental Quality Review Act, the State Historic Preservation Act, the Waterfront Revitalization and Coastal Resources Act, and the New York Coastal Management Program. The practice of open water disposal in Long Island Sound utilizes one of the following management strategies: 1. Unconfined Open Water Disposal: A process by which material deemed to be environmentally safe is deposited at a given site. 2. Confined Open Water Disposal: A process by which sediments not suitable for unconfined open water disposal are deposited and then covered or "capped" with environmentally safe material. A variation of this method occurs when previous sediment mounds are used to form a ring into which material not suitable for unconfined open water disposal can be placed and then capped accordingly. The datalayer was originally created from information provided by: (1) Carey, D., Valente R., Murray P., and Rhoads, D. 1998. State of Connecticut Dept. of Environmental Protection Office of Long Island Sound Programs Dredged Sediment Management Study: Long Island Sound Dredged Material Management Approach. SAIC Peport No. 442, Science Applications International Corporation. Appendix F.; and (2) Various US ACOE DAMOS Monitoring Cruise Reports, 1991-2000. Updates for the 2005 edition included information from The Final Rulemaking and Response to Comments Document for the Final Environmental Impact Statement (FEIS) for the Designation of Dredged Material Disposal Sites in Central and Western Long Island Sound, US Environmental Protection Agency, May 19, 2005.

As part of the overall management approach, the four sites have been extensively monitored by the US Army Corps of Engineer's (ACOE) Disposal Area MOnitoring System (DAMOS) since 1977. Each site is briefly summarized as follows: Western Long Island Sound Disposal Site: The Western Long Island Sound Disposal Site (WLIS) is located 4.63 km south of Long Neck Point, CT. Dredged material has been deposited annually at the 5.35 km2 site since 1982 and consists mainly of fine silts and clays. Sensitive local resources and public concern limit disposal to material with only low levels of contamination, therefore, only unconfined open water disposal is employed. WLIS has been extensively monitored by the DAMOS program since the mid 1980's. Feature data updated as of 2005. Central Long Island Sound Disposal Site: The Central Long Island Sound Disposal Site (CLIS) was designated in 1979 and incorporates a previous disposa

--- Original source retains full ownership of the source dataset ---

LIS Dredged Material Disposal Sites is a polygon feature-based layer that depicts the official locations of the four active (currently used) sites for depositing sediments approved for open water disposal in Long Island Sound. It does not include historic or discontinued disposal sites. The layer was compiled initially between 1999 and 2001 and depicts current conditions. Compilation scale is unknown. Attribute information is comprised of codes to uniquely identify individual features (locations of dredge disposal sites), encode the features, and cartographically represent (symbolize) these features on a map. This layer is updated as needed. Disposal activities in Long Island Sound are regulated by the following Federal statutes: the Clean Water Acts of 1977, the Coastal Zone Management Act, the Endangered Species Act of 1973, the Marine Protection, Research, and Sanctuaries Act of 1972, the National Environmental Policy Act of 1969, the Fish and Wildlife Coordination Act of 1958, and the Rivers and Harbors Act of 1899. In addition to Federal oversight, both Connecticut and New York also regulate open water disposal in the waters of Long Island Sound. In Connecticut, authority stems from the state's Structures, Dredging and Fill statute, the Tidal Wetlands statute, and the Connecticut Coastal Management Act. In New York, disposal is regulated through the Use and Protection of Waters Regulation, the Tidal Wetlands Use Regulations, the Coastal Erosion Management Regulations, the State Environmental Quality Review Act, the State Historic Preservation Act, the Waterfront Revitalization and Coastal Resources Act, and the New York Coastal Management Program. The practice of open water disposal in Long Island Sound utilizes one of the following management strategies: 1. Unconfined Open Water Disposal: A process by which material deemed to be environmentally safe is deposited at a given site. 2. Confined Open Water Disposal: A process by which sediments not suitable for unconfined open water disposal are deposited and then covered or "capped" with environmentally safe material. A variation of this method occurs when previous sediment mounds are used to form a ring into which material not suitable for unconfined open water disposal can be placed and then capped accordingly. The datalayer was originally created from information provided by: (1) Carey, D., Valente R., Murray P., and Rhoads, D. 1998. State of Connecticut Dept. of Environmental Protection Office of Long Island Sound Programs Dredged Sediment Management Study: Long Island Sound Dredged Material Management Approach. SAIC Peport No. 442, Science Applications International Corporation. Appendix F.; and (2) Various US ACOE DAMOS Monitoring Cruise Reports, 1991-2000. Updates for the 2005 edition included information from The Final Rulemaking and Response to Comments Document for the Final Environmental Impact Statement (FEIS) for the Designation of Dredged Material Disposal Sites in Central and Western Long Island Sound, US Environmental Protection Agency, May 19, 2005.

As part of the overall management approach, the four sites have been extensively monitored by the US Army Corps of Engineer's (ACOE) Disposal Area MOnitoring System (DAMOS) since 1977. Each site is briefly summarized as follows: Western Long Island Sound Disposal Site: The Western Long Island Sound Disposal Site (WLIS) is located 4.63 km south of Long Neck Point, CT. Dredged material has been deposited annually at the 5.35 km2 site since 1982 and consists mainly of fine silts and clays. Sensitive local resources and public concern limit disposal to material with only low levels of contamination, therefore, only unconfined open water disposal is employed. WLIS has been extensively monitored by the DAMOS program since the mid 1980's. Feature data updated as of 2005. Central Long Island Sound Disposal Site: The Central Long Island Sound Disposal Site (CLIS) was designated in 1979 and incorporates a previous disposal area, the New Haven Disposal Site, that was in use since 1972. Currently, CLIS encompasses an area of 8.26 km2 and is located approximately 10.37 km south of South End Point in East Haven CT. Because of its centralized location in Long Island Sound CLIS has been one of the most historically active disposal sites in New England. Characterized by predominantly silty material, CLIS mainly uses a confined disposal strategy, and the site has been monitored by DAMOS since 1977. Feature data updated as of 2005. Cornfield Shoals Disposal Site: The Cornfield Shoals Disposal Site (CSDS) was designated for dredged material disposal in 1976 and is located 6.12 km southeast of Cornfield Point, Old Saybrook, CT. Because of strong tidal currents in the area material deposited at CSDS is usually dispersed following release, often being transported outside the boundaries of the 3.42 km2 site. Therefore material disposed at CSDS cannot be capped and must be shown to have no adverse impact to the environment. Average annual disposal volumes at CSDS are much less than the other sites, and are typically characterized by sandy sediments. Disposal is restricted from June 1 through September 30 to protect lobster fishing and oyster spawning during the summer. CSDS has been monitored by the DAMOS program since 1978. New London Disposal Site: The New London Disposal Site (NLDS) is located 5.38 km south of Eastern Point in Groton, CT. The 3.42 km2 site is the shallowest of the four sites, ranging in depth from 14 to 24 meters, and has two distinct management areas within its boundaries. One is the 300 meter wide submarine transit corridor to allow passage for submarines to the US Navy base in Groton, CT, and the other is the New York-Connecticut state boundary line (approximately 0.43 km2 of the south east corner of NLDS lies in New York state waters.) Similar to CLIS, confined disposal methods are suitable for NLDS. Because of lobster fishing and oyster spawning during the summer, disposal is restricted at CLIS from June 1 through September 30. NLDS has been actively monitored by DAMOS since 1977.

An area of the bottom of a body of water which has been deepened by dredging.

S-57 Object Class: Dredged area

S-57 Acronym: DRGARE

This data was compiled for the use in the scale range 1:90,000 to 1:350,000.

THIS DATA DOES NOT REPLACE NAUTICAL CHARTS AND MUST NOT BE USED FOR NAVIGATION.

This data is based on the S-57 data format used in Electronic Navigational Charts (ENCs) published and maintained by the New Zealand Hydrographic Authority at Land Information New Zealand (LINZ). Refer to the following link for information about S-57 data: http://www.linz.govt.nz/hydro/regulation/

The effects of intensive hydraulic cockle dredging during one tidal cycle on the sediment and infaunal community compostion of two areas of sediment flat were studied during the period June 1989 - January 1990. The 2 areas selected for the study were on the mid-shore of Lavan Sands, N Wales and on the mid-shore of Blackshaw Flats, Solway Firth. The infaunal community of the Lavan Sands (LS) sites were dominated by the cockle C. edule, the baltic tellin shell M. balthica, the lugworm A. marina and the amphipod C. arenarium, with a variety of small polychaetes and other infaunal species. The infaunal community of Blackshaw Flats (BF) sites was less diverse, and dominated by cockles, baltic tellin shells and the small snail H. ulvae, with a variety of other small infaunal species. 6 sites were established in each area, 3 to act as controls for the 3 experimental sites which were dredged during one tidal cycle during June (LS) or July (BF). The sites were sampled for infaunal and sedimentological analyses on the day before dredging and then one day, one week, 3 months and 6 months after dredging. The data were analysed with the aid of a variety of statistical and graphical techniques. Prior to dredging, there was only a smally variability between the sediment characteristics of the 6 sites, at both LS and BF. However, the abundances of many infaunal species varied significantly between sites and between the control and experimental areas, particularly at LS. This is considered to be due extreme patchiness in the distribution patterns of the infauna, rather than to differences in the environmental characteristics of the sites. Comparison of the experimental sites the day before and the day after dredging found very few differences in sediment characteristics, although there was a small but significant increase in the mean grain size of the sediment at BF. There was no significant difference in the precentage mud content. Immediate effects on the infauna at LS were considerable, with significant reductions in the abundances of most species. The total number of recorded taxa dropped from 27 the day before to 20 the day after. The mean abundance of all individuals was reduced from 7,000 to 3,300 per squ. m, while the precentage reduction in abundance of most individual species was around 50%. However, at BF the effects were less dramatic, with significant reductions of only one species H. ulvae, reduced from a mean abundance of 3.313 to 1.293 per squ. m. Analysis of seasonal trends at all sites over the 6 months after dredging found that the sediment characteristics showed very little variation at either LS or BF. The percentage organic matter of the LS sites did show a small but significant reduction from summer to winter, at both the control and experimental sites. Seasonal variations in the fauna, however, were significant for most species, and at LS there was a peak in the abundance of most species in the October samples. At BF the individual species showed very different trends from each other. Comparison of the control and experimental sites over the 6 month 'recovery period' found that the fauna appeared to have recovered from the efects of the dredging within 3 months, and few effects were visible 1 week after dredging. Although there were significant differences in some faunal parameters at all sampling times, these differences were probably due to natural variation.

Abstract

Environmental degradation has continued to pose threat to the sustainability of Africa's natural resources endowment. Increasing demand for sand for construction purposes and the supply gap created by dredging on land has made river/sea sand dredging a major threat to aquatic habitat and artisanal. The importance of artisanal fishing as a source of animal protein and means of livelihood cannot be over emphasized bearing in mind particularly the high level of unemployment in Nigeria.

It is therefore imperative to determine the economic burden of sand dredging on the artisanal fishing using cross-sectional data collected through structured questionnaires from Ikorodu and Epe local government areas of Lagos state. The survey intends to identify the sand dredging and non-dredging fishing sites. The survey is aimed at comparing fish production per day, distance covered (km), labor-hour utilized per kg of fish caught and cost and returns of fishermen in sand dredging and non-dredging areas of study.

Geographic coverage

Lagos state Ikorodu Local Government Epe Local Government

Analysis unit

Individual

Universe

Individual artisanal fishing follks

Kind of data

Sample survey data [ssd]

Sampling procedure

Data were collected using two-stage sampling technique (purposive and simple random). The two Local Government Areas (LGAs) as well as the nine communities that spread across the two LGAs were purposively selected because they are known for artisanal fishing.

The nine fishing communities sampled in the two LGAs are Oreta, Majidun, Itoikin, Ofin, Bayeku, Ijede, Ejinrin, Elubo and Iponmi via Agura Gberigbe. These communities are not only known for fishing but also for intensive sand dredging which provides sand for construction firms. In the second stage fifty (50) respondents were randomly selected from each of the nine fishing communities.

A total of 450 questionnaires that addressed the objective of the study were administered while 332 were returned.

Sampling deviation

No deviation

Mode of data collection

Face-to-face [f2f]

Research instrument

The questionnaire is divided into six (6) sections: Section A: Socioeconomic characteristics Section B: Fishing as an occupation Section C: Sand dredging Section D: Cost of fishing Section E: Returns on artisanal fishing Section F: Constraint to artisanal fishing

Cleaning operations

Manual editing was carried out to remove duplicated questionnaires. Also removed were questionnaires that respondents failed to provide answers to key questions on the quantity of fish caught, the cost items, the status of the location (whether sand dredging is taking placeor not), fishing hours per day among others. Questionnaires that filled with ambiguous data such as falsified quantity of fish caught per day were removed.

Microsoft Excel was used for data entering. Data editing took place during data entering and structure checking and completeness.

Response rate

The response rate was approximately 74%

(A total of 450 questionnaires that addressed the objective of the study were administered while 332 were returned).

Sampling error estimates

No sampling error

Data appraisal

No other form of data appraisal