Showing papers on "Dredging published in 2013"
TL;DR: In this paper, the authors focus on the San Francisco Bay Coastal System, extending from the lower San Joaquin-Sacramento Delta, through the Bay, and along the adjacent outer Pacific Coast.
84 citations
TL;DR: Wang et al. as mentioned in this paper collected sediment-water microcosms for evaluating the effects of dredging on nitrogen cycling and found that dredging may lead to ammonia release to water column in a short term, while ammonia release risk is low few years after dredging.
67 citations
TL;DR: It is found that higher intensities of dredging caused the dolphins to spend less time in the harbour, despite high baseline levels of disturbance and the importance of the area as a foraging patch.
65 citations
TL;DR: In this article, an analysis of these activities through time and morphodynamic response of the lower Oka estuarine system is presented, and the relationships between both processes have been established.
65 citations
TL;DR: In this paper, the authors conducted repeat underwater camera surveys inside a recently established area that is permanently closed to scallop fishing and a seasonally fished area in Cardigan Bay, UK, to test for differences in scallops abundance and epibenthic community structure and examine recovery processes over a 23 mo study period.
Abstract: Fishing with bottom towed gear is widely considered an invasive form of fishing in terms of its impacts upon seabed habitats and fauna. Fishery closures or marine protected areas provide baseline conditions against which to assess the response to the removal of fishing disturbance and thus shed light on their use as fisheries management tools. We conducted repeat underwater camera surveys inside a recently established area that is permanently closed to scallop fishing and a seasonally fished area in Cardigan Bay, UK, to test for differences in scallop abundance and epibenthic community structure and to examine recovery processes over a 23 mo study period. Changes in scallop density and epifaunal diversity and community composition were primarily driven by seasonal fluctuations; no differences were found between the permanently closed area and the seasonally fished area. Temporal changes in epibenthic community inside the permanently closed area were not related to recovery processes associated with the cessation of scallop dredging. Sediment composition and bedforms shifted between surveys, suggesting that this community is exposed to a dynamic environment. It is likely that scallop dredging at the present levels of fishing may be insufficient to induce changes large enough to be detected in the presence of strong natural disturbance. We highlight the importance of considering the physical nature and dynamics of the environment and the nature of the species concerned throughout the process of designating closed areas, to avoid negative impacts on fisheries and limited conservation benefits.
45 citations
TL;DR: In this article, a multi-faceted provenance study was performed to definitively establish the primary sources, sinks, and transport pathways of beach-sized sand in the region, thereby identifying the activities and processes that directly limit supply to the outer coast.
45 citations
TL;DR: A new procedure is presented for the planning of dredging that reduces the environmental impacts by reducing the amount of dredged sediments and, at the same time, reduces costs and as the size of the CDF is significantly smaller, less dredging is necessary, causing smaller environmental impact.
45 citations
TL;DR: The findings show that creation of the artificial island with the underwater explosion sediment removal technique would greatly impact the marine environment, however, the impact for the silt dredging technique would be less.
32 citations
TL;DR: In this article, the impacts of various phosphorus load reduction scenarios on nutrient concentrations in Lake Uluabat, a Ramsar site (a wetland of international importance designated under the Ramsar Convention), including sediment dredging options and source reduction, were simulated.
26 citations
03 Jan 2013
TL;DR: In this paper, a thoroughly researched book, written by noted experts, takes the reader step-by-step through the complex development of a hydraulic fi ll project, showing that without proper hydraulic equipment and suitable specialised equipment, many major infrastructure projects such as ports, airports, roads, industrial or housing projects could not be realized.
Abstract: Without proper hydraulic fi ll and suitable specialised equipment, many major infrastructure projects such as ports, airports, roads, industrial or housing projects could not be realised. Yet comprehensive information about hydraulic fi ll is diffi cult to fi nd. This thoroughly researched book, written by noted experts, takes the reader step-by-step through the complex development of a hydraulic fi ll project.
25 citations
TL;DR: In this article, the effects of dredging on macrobenthic communities were investigated in the Mondego estuary, Portugal, between 2007 and 2008, within and around the area to be dredged.
TL;DR: In this paper, a leachate testing method was applied to contaminated sediments to simulate migration of potential contaminants in groundwater, and the results showed that most dredge spoils could be disposed of in privately owned or provincially operated landfill sites, providing less expensive disposal options compared to containment cells.
Abstract: Sediment dredge disposal options were reviewed to improve cost-effectiveness and environmental safety for dredging of coastal sediments at the Department of Fisheries and Oceans Small Craft Harbours (DFO-SCH) program in Canada. Historically, contaminated dredge sediments exceeding federal guidelines were disposed of in nearby landfills. Recent federal regulatory changes in sediment quality guidelines adopted by provincial regulators in Canada has resulted in updates to guidelines for disposal of contaminated solids in landfills. Updates now require specific and general disposal options for contaminated dredge material destined for land-based disposal, resulting in more expensive disposal in containment cells (if contaminated sediments exceed federal guidelines). However, as part of this study, a leachate testing method was applied to contaminated sediments to simulate migration of potential contaminants in groundwater. Using this approach, leachate quality was compared to federal freshwater criteria and drinking water quality guidelines for compliance with new regulations. Leachate testing performed on the highest sediment contaminant concentrations triggered less than 2 percent potable water exceedances, meaning that most dredge spoils could be disposed of in privately owned or provincially operated landfill sites, providing less expensive disposal options compared to containment cell disposal. Current dredge disposal practices were reviewed at 35 harbor sites across Nova Scotia and their limitations identified in a gap analysis. Improved site management was developed following this review and consultation with interested marine stakeholders. New disposal options and chemical analyses were proposed, along with improvements to cost efficiencies for management of dredged marine sediments in Atlantic Canada. © 2013 Wiley Periodicals, Inc.
01 Nov 2013
TL;DR: In this article, the authors assessed the evolution of sedimentation in the Abrolhos coastal reefs during the past decades by analyzing samples from sediment cores collected near the reefs of Coroa Vermelha (located 15 km from the coast), Pedra de Leste and Popa Verde.
Abstract: Coral reefs of the coastal area of Abrolhos are located in an environment with a high influx of terrigenous sediments that are carried out to the sea, either as a result of natural processes (river output, coastal erosion, and torrents) or due to anthropogenic influences (deforestation, coastal development, and dredging). Excessive terrigenous sediment in coastal areas has been identified as one of the major threats to coral reefs, leading to their worldwide decline. The present study assessed the evolution of sedimentation in the Abrolhos coastal reefs during the past decades by analyzing samples from sediment cores collected near the reefs of Coroa Vermelha (located 15 km from the coast), Pedra de Leste (located 12 km from the coast) and Popa Verde (located 35 km from the coast). The purpose of this assessment was to observe whether the previously described pattern of surficial bottom sediment distribution in Abrolhos, which consisted of terrigenous mud in the nearshore reefs, to carbonate-dominant sediments towards the offshore reefs, is still a prevalent feature. Sediment color, texture, CaCO3 percentage, biogenic compounds and clay minerals, as well as the sedimentation rate and the geochronology of the sediment cores were analyzed. The results showed indications of an increase in the deposition of terrigenous mud, over the last decade, in the vicinity of the reefs nearest to the coast, though this does not yet constitute a definitive evidence of such a change. However, this observation therefore suggests that local processes resulting from anthropogenic actions are most likely causing an increase of the sedimentation rate of continent-derived sediment runoff in the Abrolhos coastal areas. To minimize this situation, there is an urgent need for the development of new management strategies to protect the already disturbed Abrolhos coastal reefs, especially during times of global changes.
TL;DR: The vertical stratification of sediment concentration and of animal numbers in the water column suggests that even if some of these species respond actively to the presence of the dredge, once entrained, they are transported more or less passively in the same way as the larger sediment particles.
TL;DR: In this paper, the authors investigated the socioeconomic effects of a dredging process on the Bahia Blanca Estuary System. And they found that the economic cost of the dredging related with the project is between US$ 5 million and US$ 6.5 million depending on how the displaced labor force can be reallocated.
TL;DR: In this article, the marginal costs of agricultural best management practices (BMP) implementation become >$6.90/t of sediment reduction, then dredging becomes the economically preferred alternative.
Abstract: Erosion of agricultural cropland has been identified as a major source of sediment accumulating in water reservoirs. Emphasis is increasingly on finding the most cost-effective ways to control soil erosion to reduce reservoir sedimentation. In this study, biophysical and economic models for the Tuttle Creek Lake watershed in northeastern Kansas were integrated to determine if implementation of alternative cropland management strategies to reduce reservoir sediment are more cost-effective than dredging. In the Tuttle Creek Lake watershed, we found that if the marginal costs of agricultural best management practices (BMP) implementation become >$6.90/t of sediment reduction, then dredging becomes the economically preferred alternative. Meeting this cost requires that BMP in the form of filter strips and no-till cultivation are implemented in a targeted, cost-effective manner, not in a random pattern of voluntary adoption that may characterize BMP adoption in some watersheds. Although reservoir dred...
TL;DR: In this article, the mineralogical compositions of 119 samples collected from throughout the San Francisco Bay coastal system, including bay floor and seafloor, area beaches, cliff outcrops, and major drainages, were determined using X-ray diffraction (XRD).
TL;DR: In this paper, the authors investigate the effect that freshwater inflow has on the transport of dredged material in Liverpool Bay, and show that sediment dispersal is first simulated using constant density throughout the domain, and then density gradients and stratification will be allowed to develop from riverine inputs.
Abstract: This study investigates the effect that freshwater inflow has on the transport of dredged material in Liverpool Bay. The sediment dispersal is first simulated using constant density throughout the domain, and then density gradients and stratification will be allowed to develop from riverine inputs. The first case shows the sediments slowly being transported east-westwards away from the estuary; while the simulation with freshwater shows the sediment being rapidly transported south-eastward towards the estuary. Model simulations such as these may inform decisions of where to put the dredging spoil to minimise the likelihood of it returning directly to the estuary.
TL;DR: The impact of dredging on water quality of Igbedi Creek, upper Nun River, Niger Delta was investigated from June 2009 to May 2011 as mentioned in this paper, which revealed significant spatial differences (P<0.05) between the locations in all the water quality parameters measured except for DO, Temp. and pH.
Abstract: The impact of dredging on water quality of Igbedi Creek, upper Nun River, Niger Delta was investigated from June 2009 to May 2011. Two locations – Ogobiri (Dredged) and Agoro-Gbene (Un-dredged) were studied. Two locations – Ogobiri (Dredged Location) and Agoro-Gbene (Un-dredged Location) were studied. For the purpose of this study, the selected dredged and non-dredged sites were divided into stations: Ogobiri – OGO1DA=Dredged Area, OGOI&2DS=Downstream, OGO1&2US=Upstream; Agoro-gbene – AGO1DS=Downstream, AGO1MD=Midstream, AGO1US=Upstream. The data revealed significant spatial differences (P<0.05) between the locations in all the water quality parameters measured except for DO, Temp. and pH. There were significant temporal variations as well between the locations in the following parameters: Temperature, Turbidity, Conductivity, N03 , NO2 , S04 2, and BOD5. The results further showed high increase in values for Turbidity and NO2 in the station immediately downstream of the dredged area but steadily declined downstream. These results are clear indications that dredging significantly affected the water quality of the
TL;DR: In this article, a vessel equipped with a vertical acoustic Doppler current profiler and a conductivity-temperature-depth probe with a turbidimeter followed the different dredges during their daily operations.
Abstract: The turbid plumes generated by different types of dredges have specific behaviours and diffusion patterns. The dredging of the Oil Port of Genoa Multedo (Italy) with three different dredges (grab, backhoe and trailing suction hopper) enabled us to study: the physical and hydrodynamic characteristics of the water column of the port and the area just outside it; the characteristics of the turbid plumes; and the different responses of our optical and acoustic instruments. In the dredging operations, a vessel equipped with a vertical acoustic Doppler current profiler and a conductivity–temperature–depth probe with a turbidimeter followed the different dredges during their daily operations. Using the acoustic backscatter and turbidity data acquired during the dredging phase, we investigated the turbidity variations caused by the dredging operations to study the evolution of the plume generated by the three different dredges. The grab plume was present only on the bottom up to a distance of 50 m from the grab, while at greater distances the turbidity fell to background values. The backhoe plume was present close to the bottom at a distance of 50 m from the dredging and, in the entire water column, at distances of 50–400 and 100 m inside and outside of the port, respectively. The trailing suction hopper dredge plume extended from the surface through the entire water column at distances from the dredging of 400 and 100 m inside and outside of the port, respectively. The highest values were found close to the bottom at distances from the dredging at 50 and 30 m inside and outside of the port, respectively. The choice of a combined monitoring system is a good practical solution for studying the differences between the turbid plumes created by the three dredging tools (grab, backhoe and trailing suction hopper dredge) under different hydrodynamic conditions. Furthermore, two different types of instrument should give complementary information on different aspects of sediment resuspension during a dredging operation.
TL;DR: In this paper, the authors proposed integer programming models and heuristic solution algorithms to select maintenance dredging projects for funding, while taking into account interdependent benefits, and tested on example port systems from the Great Lakes region and from mainline coastal ports and inland waterways.
Abstract: Budget allocation to annual maintenance dredging projects conducted by the U. S. Army Corps of Engineers is addressed. Of the many projects requested, only a subset may be selected for funding because of budgetary constraints. The benefits of conducting maintenance dredging at one dredging project depend on other projects in the system that also are being dredged to take advantage of transportation efficiency gains derived from deeper navigable waterways. The proposed integer programming models and heuristic solution algorithms selected dredging projects for funding, while taking into account interdependent benefits. The models considered the waterway network topology, which was derived from flow data of historic waterborne cargo. The solution algorithms ensured efficient computational performance and quality of solutions. The models and algorithms were tested on example port systems from the Great Lakes region, as well as from mainline coastal ports and inland waterways. The models were shown to increase...
TL;DR: Morang et al. as discussed by the authors studied regional sediment processes, sediment supply, and their impact on the Lousiana coast and found that sediment supply and sediment processes are correlated with changes in coastal ecosystems of the Northern Gulf of Mexico.
Abstract: Morang, A.; Rosati, J.D., and King, D.B., 2013. Regional sediment processes, sediment supply, and their impact on the Lousiana coast. In: Brock, J.C.; Barras, J.A., and Williams, S.J. (eds.), Understanding and Predicting Change in the Coastal Ecosystems of the Northern Gulf of Mexico, Journal of Coastal Research, Special Issue No. 63, pp. 141–165, Coconut Creek (Florida), ISSN 0749-0208.
TL;DR: In this article, the authors examined two sand budget components in the lower Columbia tidal river, fluvial supply and human removal, and found that a sand deficit has existed for >50 of the last 85 years.
Abstract: Long-term changes in the sand balance of a river-estuary system can strongly affect navigation and ecosystems. Here, we examine two sand budget components in the lower Columbia tidal river, fluvial supply and human removal. Rating curves were used to estimate daily sand input between 1900 and 2010. Publications, interviews, and data analyses were used to evaluate sand removal by dredging and mining. Comparison between sand input and removal indicates that a sand deficit has existed for >50 of the last 85 years. Since 1962, the deficit has averaged 4.62 (±1.74)×106 ts-yr−1. Although historic sand transport to the ocean cannot be estimated, it is now small. Several factors contribute to the sand deficit: dredging, sand mining, flow regulation by dams, and climate change. The sand deficit documented here has likely contributed to the lower water levels in the tidal river observed in recent decades, which decreases habitat availability during high flows and channel depths during low-flow periods.
TL;DR: In this article, numerical and experimental investigations were conducted to study the sediment transport and deposition in this target area, and the accumulated sediment deposition on the seabed and wetland surface were calculated.
TL;DR: In this paper, an analysis of the effect of climate change on modifying the dredging cost to maintain the navigation channel at the actual capacity of the Parana waterway (Argentina) is presented.
Abstract: This paper presents an analysis of the effect of climate change on modifying the dredging cost to maintain the navigation channel at the actual capacity of the Parana waterway (Argentina). The Parana−Paraguay Rivers system is one of the most important inner navigation waterways in the world, where approximately 100 million tons of cargo are transported per year. Maintenance of the navigation channel requires continuous dredging by Hidrovia SA (limited liability company), which is responsible for ensuring the minimum water depth for navigation. A failure event occurred during January 2012 when a bulk cargo carrier ran aground, interrupting fluvial trading for 10 days. Numerical models were applied to simulate hydro-sedimentation processes at the Lower Parana River to estimate dredging costs for a given flow discharge. The resulting function relates the sedimentation rate (i.e. the dredging effort required to keep the present depth for vessel draft) to forcing hydrology conditions. This function and the sta...
TL;DR: The selection of the best site for the placement of dredged sedimentary material from the Aliveri coastal area in the adjacent South Euboean Gulf (Greece) was accomplished through a screening procedure based on a cluster analysis, which tested the physicochemical resemblance of the dredged material and the surface sediments of 19 potential placement locations in the gulf.
Abstract: The selection of the best site for the placement of dredged sedimentary material (∼7,000 m3) from the Aliveri coastal area in the adjacent South Euboean Gulf (Greece) was accomplished through a screening procedure. The initial stage comprised the determination of physical, chemical, and biological characteristics of the dredged sediment before the commencement of any dredging operation. Grain size measurements, geochemical analyses together with the use of pollution/toxicity indices and empirical sediment quality guidelines, and the conduct of an acute toxicity test showed that the dredged material consisted of “unpolluted to slightly polluted” silty sands and sandy silts. However, the local authorities planned to place this sediment in the neighboring open sea area, i.e., the South Euboean Gulf, due to the absence of any beneficial use or alternative dumping option (i.e., dumping on public lands). Therefore, the next stage of the screening procedure, based on criteria such as the national legislation, seabed and seawater column characteristics, influence of the water mass circulation pattern on the post-placement migration of dredged sediment, impact on living resources and human activities (i.e., aquaculture and fishing), effect on significant marine sites (i.e., sites of scientific, ecological, and historical importance, navigation routes, military zones), and seafloor engineering uses, led to the evaluation of the suitability of the South Euboean Gulf as a potential dumping area. Then, the identification of the appropriate dredged material placement sites in the South Euboean Gulf was based on a cluster analysis, which tested the physicochemical resemblance of the dredged material and the surface sediments of 19 potential placement locations in the gulf. After the statistical process, only four sites situated near the north shoreline of the South Euboean Gulf were qualified as the best dredged material placement locations.
TL;DR: Duclos et al. as discussed by the authors studied the dynamics of turbid plume formed by the overflow at an experimental dredging site (0.6 km2), located in the Bay of Seine (eastern English Channel), a macrotidal environment where the seabed is composed of sandy gravel.
Abstract: Duclos, P.-A.; Lafite, R.; Le Bot, S.; Rivoalen, E., and Cuvilliez, A., 2013. Dynamics of turbid plumes generated by marine aggregate dredging: an example of a macrotidal environment (the Bay of Seine, France). On the French marine shelf, marine aggregates are currently dredged by trailing suction hopper dredgers (TSHD), without screening, with an overflow process, with or against currents. In the framework of the Groupement d'Interet Scientifique (GIS) Suivi des Impacts de l'Extraction de Granulats Marins (SIEGMA), the dynamics of the turbid plume formed by the overflow was studied at an experimental dredging site (0.6 km2), located in the Bay of Seine (eastern English Channel), a macrotidal environment where the seabed is composed of sandy gravel. An original field strategy based on Lagrangian monitoring, using the back-scattered signal of an Acoustic Doppler Current Profiler (ADCP), Laser In Situ Scattering and Transmissometry (LISST) measurements, water samples, and aerial photographs, has sh...
TL;DR: In this paper, the authors evaluated the quality of dredging sediments through an integrated chemical-ecotoxicological approach and defined suitable management options for the harbour of Fiumicino, Italy.
Abstract: In order to assess sediment quality and to account for the great geochemical heterogeneity of Italian coasts, Local Sediment Quality Guidelines (LSQGs) have to be defined for specific portions of the coastline based on the approach developed by ICRAM–APAT (2007). This paper describes the application of LSQGs to the harbour of Fiumicino (Rome, Italy). The aims were to evaluate the quality of dredging sediments through an integrated chemical–ecotoxicological approach and to define suitable management options. Thirty-eight sediment cores, covering the planned dredging depth, were collected in the study area and sliced into 92 sediment samples. Chemical analyses, including inorganic and organic contaminants as well as microbiological parameters, were carried out for all the samples. A bioassay battery composed by the bacterium Vibrio fischeri, the sea urchin Paracentrotus lividus and the alga Dunaliella tertiolecta was applied on one third of the samples. LSQGs were derived from chemical and ecotoxicological data of the harbour area, and were integrated with those from the identified dumping site. The Baseline Chemical Level, corresponding to an absent or unlikely ecotoxicological hazard, and the Limit Chemical Level, corresponding to a probable ecotoxicological hazard, were the LSQGs derived for each chemical. A gradient of increasing contamination, moving inland due to urban and agricultural effluents, was observed. Ecotoxicological analyses, similar to microbiological ones, confirmed the poor sediment quality, with the exception of a sample located at the port entrance, where hydrodynamics flush sediment away from the site. Principal component analysis allowed a clear discrimination of three areas, each affected by a different contamination degree and influenced by many sources related to industrial, commercial and/or urban activities. Using LSQGs and the results of bioassays, it was possible to classify the sediment quality of the whole harbour area and to define the most suitable management options. It was found that Fiumicino harbour sediment was not suitable for either beach nourishment or for offshore dumping, with the exception of a negligible amount located at the port entrance. In turn, most sediment seemed to be suitable for disposal in a properly sealed confined disposal facility or for mechanical/chemical treatment. This case study provided useful insights for implementing the development of LSQGs for more realistic sediment management and will assist in promoting its application to harbour dredging at the local level.