A Área Portuária do Maranhão, situada na costa ocidental da Ilha de São Luís, na Baía de São Marcos, constitui-se no segundo maior complexo portuário da América Latina e um dos maiores do mundo em termos de movimentação de carga. Esta área portuária abrange o Complexo Portuário de Ponta da Madeira, da CVRD - Companhia Vale do Rio Doce S. A., o Porto de Itaqui, da EMAP - Empresa Maranhense de Administração Portuária e o Porto da ALUMAR, da Alcoa, Alcan, BHPBilliton e Abalco. A caracterização da hidrosedimentologia do Canal de Acesso do Complexo Portuário do Maranhão foi conduzida a partir da compilação e análise dos dados de correntes existentes e da aplicação de modelagem computacional. A caracterização das conformações de fundo foi efetuada a partir da análise de mais de 20 anos de sondagens batimétricas nas áreas de interesse do Canal de Acesso. Com a caracterização da área pretende-se fornecer subsídios à Engenharia Portuária, possibilitando o planejamento de sondagens batimétricas e dragagens de manutenção do Canal. Este trabalho também contempla uma metodologia para fornecimento de previsão de campos de corrente, a partir dos resultados das simulações hidrodinâmicas, e o fornecimento de previsão da evolução e migração das conformações de fundo. A evolução das isóbatas na Área IV mostra que as formações de ondas de areia não evidenciam significativa mudança de posição com o tempo. Em compensação, a Área I, apresenta conformações de fundo com irregularidade da forma de onda, evidenciando que existe uma maior migração destas. O modelo de transporte de sedimentos indicou pequeno transporte resultante nas Áreas IV, III e II, que explica a reduzida migração dessas ondas quando comparadas com a Área I. A determinação das ondas críticas para cada Área constitui-se instrumento na operação portuária, permitindo redução da área hidrografada para definir a tomada de decisão quanto à nova dragagem. / The Maranhão Harbour Area is the second biggest harbour Complex of Latin America and one of biggest of the world in cargo handling is located at the western coast of São Luís Island in São Marcos Bay, this harbour area is composed by the Complex of Ponta da Madeira of CVRD - Companhia Vale do Rio Doce S. A., the Itaqui Harbour, of EMAP - Empresa Maranhense de Administração Portuária and the Alumar Harbour, of Alcoa, Alcan, BHPBilliton and Abalco. The hydrossedimentological characterization of the Access Channel of Maranhão Harbour Area was achieved from current data review and analysis for numerical modeling application. The bottom sand waves description was made from more than 20 years bathymetrical surveys in the interest Areas of the Access Channel. The purpose of this characterization was to improve Harbour Engineering activities, the planning and scheduling of depth surveys campaigns and dredging maintenance. This thesis also provides an approach to get current patterns predictions from the results of the hydrodynamical simulation, and for the prediction of the evolution and the migration of sand waves. The Area IV bottom evolution shows that the sand waves have not significative temporal position shifting. Otherwise, in Area I bed forms have more irregular pattern, showing major wave migration. The sediment transport model pointed to a small sediment transport rate in Area IV, III and II, explaining the smaller migration pattern of these waves when compared with Area I. The critical wave definition in each Area can be an harbour operation tool, reducing the surveyed area needed to take a new dredging maintenance decision.

O crescimento da atividade econômica nacional na movimentação de granéis sólidos e líquidos, bem como na carga geral, vem exigindo o desenvolvimento de uma política especial para o setor de dragagem, de modo a eliminar os passivos existentes nos portos públicos relativos à expansão das atividades portuárias. Dentro desta necessidade de crescimento, as condicionantes ambientais devem ser muito bem avaliadas e integradas aos projetos de dragagem na forma de Estudos de Impactos Ambientais, oferecendo subsídios para o desenvolvimento das atividades e garantindo o controle dos impactos ambientais, através de medidas preventivas, mitigadoras e/ou compensatórias. O presente trabalho avaliou as principais metodologias, equipamentos utilizados e modos de disposição do material dragado nas atividades de dragagens portuárias marítimas, assim como as diferentes variáveis para gestão das operações de escavação e disposição material em função de seus potenciais efeitos sobre o meio ambiente, oferecendo informações que possibilitem a facilitação do processo de decisões nos projetos de dragagem. Para isto, este estudo caracterizou como a gestão ambiental de dragados, com enfoque na disposição de sedimentos em locais confinados, pode influenciar na operacionalidade portuária marítima do ponto de vista técnico, social e econômico, considerando-se as legislações e recomendações vigentes no Brasil e em nível internacional. / The growth of brazilian economic loading rate of bulk solids and liquids, as well as general cargo, requires a special policy for the dredging sector, to remove the existing liabilities in the public ports for the expansion of port activities. Within this growing need, the environmental constraints must be thoroughly evaluated and integrated with dredging projects in the form of Environmental Impact Assesments, offering subsidies for the improvement of activities and ensuring control of environmental impacts through preventive, mitigating and / or allowances. This study evaluated the main methodologies, equipment used and methods of disposal of dredged material from dredging activities in the maritimes ports, and the different variables to manage operations and disposal of excavated material, on the basis of their potential environmental effects, offering information to enable the process of making decisions in dredging projects. With this purpose, the study was characterized as the environmental management of dredged material, focusing how sediments in confined disposal can influence the seaport operation in terms of technical, social and economic development, considering the international and brazilian laws and guidelines, found in Brazil and internationally.

More than a century of dredging for oysters in the Foveaux Strait has resulted in a decimated fishery. In 1999 the Parliamentary Commissioner for the Environment asked the question: Where did we go wrong? This thesis provides answers to this question by presenting information provided by the Bluff oyster fishermen. In order to gain as much exposure to the community of fishermen as possible, a cumulative period of approximately six months was spent living in the town of Bluff between 2002 and 2007. During this time relationships were built with key informants, and a total of more than 50 community members were interviewed. The thesis describes the practical knowledge of the oyster fishermen, and places it in the context of more that 40 years of modem scientific studies concerned with the fishery. The finding are that since 1996 when the Quota Management System was introduced in the fishery, the most knowledgeable and responsible people in the fishery have been systematically excluded from roles in management. The practical knowledge of fishermen has been discounted in an industry and government led management system, which is an elaborate justification for continued maximum exploitation of the fishery. The theoretical contribution of the thesis lies in its description of belonging as a factor as important as that of property-rights in a sustainable resource system. The practical knowledge and conservation-mindedness of the fishery elders are characteristics of belonging, but not necessarily of ownership. Fishery management should recognize belonging as cultural capital, and make use of it under the present system (i.e. the Quota Management System) by according fishermen rights of management and access to the oyster fishery.

Studies were conducted to broadly describe and understand the sediment benthos of a shallow-water coastal area (Aramoana Beach - Heyward Point - Blueskin Bay) near the entrance to Otago Harbour, a system largely representative for southeastern New Zealand. Benthic assemblages were examined in relation to gradients of wave exposure and disturbance, sediment type and bathymetry, and dredge-spoil disposal. Sediment and macrofaunal surveys in autumn and spring 2003 found little change in sediment texture gradients from historical studies and a lack of vertical stratification. Macrobenthic samples from spring produced significantly higher abundances of three numerically dominant phyla (Arthropoda, Annelida, and Mollusca) and higher taxon richness compared to autumn. Within water depths of 6-30 m, abundance, richness, and diversity increased with depth. Multivariate analyses identified similar assemblages among deeper sites, despite sediment textural differences, whereas distinct assemblages were found in the shallow portions of the three areas. Meiofaunal abundance patterns did not reflect those of macrofauna, possibly indicating greater vertical penetration of sediments in these hydrodynamic environments. Several new kinorhynch taxa were found. In a field manipulation, part of the Aramoana dredge-spoil dumpground was protected from spoil disposal for an extended period followed by experimental dumping of sandy and muddy spoil. Macrofaunal samples were collected before dumping and at nine sites < 119 d after disposal. Water velocities at the sediment-water interface were compared to a local sediment disturbance model. Dumpground samples were depauperate in individuals and taxa compared to an area protected from dumping for > 180 d. A drop in abundance and a dissimilar community coincided with muddy spoil, but fine sediments were dispersed within 26 d and macrofaunal assemblages recovered to the pre-existing state. Sandy spoil, while not altering native sediment textures, had a more prolonged impact due to transplantation of macrofauna from the dredged area that persisted for < 41 d after disposal. Side-scan sonar mapping indicated that the disposal footprint model used approximated the extent of sandy spoil impacts well, while local conditions spread muddy sediments beyond the initial impact site. A novel sediment profile imaging device was constructed that has many advantages over existing devices for spoil mound studies and habitat mapping: it is smaller, can be manually deployed from small boats, is cheaper, and can be modified to work in almost any soft sediment. Studies of one dominant taxon, the gastropod Zethalia zelandica, showed it was better able to survive sand burial than mud burial, did not vary in overall activity through a range of 5-14� C, and contributed a large proportion of biomass of its community. The spoil disposal strategy used does not appear as environmentally neutral as originally thought. Only muds are effectively dispersed whereas coarser sediments accumulate, affecting physical and biological benthic processes of a wider area. Two mitigation strategies were evaluated using a heuristic model. Reducing the disposal area and spreading mud disposal events over a longer time span may be an effective interim strategy. Overall, the studies will help guide management of the area.

The sediment resuspension and turbidity created during dredging operations is both an economical and environmental issue. The movement of sediment plumes created from dredging operations has been predicted with numerical modeling, however, these far-field models need a “source term” or near-field model as input. Although data from field tests have been used to create near-field models that predict the amount of material suspended in the water column, these results are skewed due to limitations such as non-uniform sediment distributions, water currents, and water quality issues. Laboratory investigations have obtained data for turbidity during dredging operations, but these results do not take advantage of the most contemporary testing methods. The purpose of this dissertation is to provide an estimation of turbidity created during a cutter suction dredging operation. This estimation was facilited by the development of resuspension measurement and data acquisition techniques in a laboratory setting. Near-field turbidity measurements around the cutter head were measured in the Haynes Coastal Engineering Laboratory at Texas A&M University. The laboratory contains a dredge/tow tank that is ideal for conducting dredging research. A dredge carriage is located in the dredge/tow tank and is composed of a carriage, cradle, and ladder. Acoustic Doppler Velocimetry (ADV) and Optical Backscatter Sensor (OBS) measurements were taken at specific points around the cutter head. The variables of suction flow rate, cutter speed, and the thickness of cut were investigated to understand their specific effect on turbidity generation and turbulence production around the cutter head. A near-field advection diffusion model was created to predict resuspension of sediment from a cutter suction dredge. The model incorporates the laboratory data to determine the velocity field as well as the turbulent diffusion. The model is validated with laboratory testing as well as field data. Conclusions from this research demonstrate undercutting consistently produced larger point specific turbidity maximum than overcutting in the laboratory testing. An increase in suction flow rate was shown to increase production and decrease turbidity around the cutter head. In general, an increase in cutter speed led to an increase in turbidity. The thickness of cut produced less resuspension for a full cut versus a partial cut. Data for a “shallow cut” also produced less turbidity generation than partial cuts. The numerical model was compared to all laboratory testing cases as well as the Calumet Harbor and New Bedford cutter resuspension data and produced suitable MRA values for all tests. The numerical model produced higher point specific regions of turbidity for undercutting but produced larger mean values of turbidity for overcutting.

This study was conducted to ascertain the impacts of bed leveling, following ship channel dredging operations, and to also investigate the hydrodynamic flow field around box bed levelers. Laboratory experiments were conducted with bed levelers operating in the laboratory using video cameras for flow visualization. Computer software and numerical codes, called FANS, were used to validate the laboratory experiments. The study was split into two major parts: laboratory experiments and hydrodynamic modeling. The laboratory experiment was conducted to model how bed levelers interact with the ship channel bottom after hopper dredge dragheads (blades) made passes and created uneven trenches. These interactions were observed using both underwater and hand-held cameras. The hydrodynamic modeling was accomplished using GRIDGEN and PEGSUS commercial software for generating grid and input data files in the pre-processing phase, Finite-Analytic Navier-Stokes (FANS) software for simulation in the processing phase, and two commercial software (Fieldview and Tecplot) for plotting the images and graphs in the post-processing phase. An interesting phenomenon was observed in the laboratory experimental runs. The flow field showed reversed flow in front of the moving bed leveler and the trench parallel to the direction of the bed leveler. The flow in the parallel trench was observed to be in the same direction as the bed leveler movement, and it was expected that the flow would travel under the bed leveler. The bed leveler was towed at two specified constant speeds: 0.25 m/s (0.82 ft/s) and 0.5 m/s (1.64 ft/s) and at a water depth of 1.22 m (4.00 ft) Similarly, the images and plots of the hydrodynamic modeling obtained from FieldView and Tecplot software showed flow reversal, depicted by the negative velocities, within the vicinity of the trench, as the model bed leveler moved past and interacted with the fluid. The negative velocity had a magnitude close to 0.5 m/s (1.64 ft/s), which was the velocity used in running the laboratory experiments. The hydrodynamic simulation matched closely with the experimental observations, and thus, the laboratory observation was confirmed. The final results obtained from the numerical modeling helped to understand the hydrodynamic effects around the box bed leveler.

Canal maintenance, involving mechanical removal of sediments and algal growth from canal basins, is necessary for sustaining the viability of the irrigation water delivery system in the Imperial Valley of California. Maintenance activities, however, disturb canal sediments laden with bacteria and can negatively impact water quality downstream. Our work quantified fecal indicator bacteria (Escherichia coli) and pathogens (Salmonella) in canal water prior to, during, and post-maintenance events. The goal of this study was to construct a post-maintenance time matrix that will allow growers downstream to estimate when canal water once again meets water quality guidelines. In addition, we assessed the water quality impacts of lining canals with concrete, which is a costly endeavor in the short term, but may be beneficial in the long term as lined canals do not require routine dredging to maintain canal integrity. During eight maintenance events from March 2013 through August 2014, 22% of 396 water samples collected exceeded the irrigation water quality guidelines (<126 MPN E. coli 100 mL-1) during canal maintenance. During summer months (July and August 2013-2014), E. coli concentrations in water samples commonly reached maximum values (>2419.6 MPN E. coli 100 mL-1), and these samples were more readily collected from unlined canal sampling sites. During winter and spring months, 80.8% of E. coli exceedances for unlined canals met guideline standards in less than 22 hours, while 19.2% of exceedances took longer (up to 48 hours) to return to acceptable levels; in lined sites, 63.6% and 36.4% met guidelines in less than 22 hours and 48 hours, respectively. Summer months showed a different trend: in unlined canal sites, 56.3% of E. coli exceedances met standards within 22 hours and 43.7% within 48 hours; in lined sites, 100% of water samples met standards in less than 22 hours. Unlined sites averaged higher temperatures overall compared to lined sites, and canal water in July (2013) was extremely warm (averaging 32.8°C) and reached human body temperature (37°C) at several unlined sites, a temperature at which enteric bacteria are known to thrive. Culturable Salmonella were detected in water samples collected in summer, with 22.2% of Salmonella-positive samples within 1°C of human body temperature. E. coli concentrations were significantly correlated with temperature and pH in unlined canals only. Unlined canals showed 15.2% of water samples were Salmonella-positive during summer maintenance whereas 1.7% of lined canals were positive. Salmonella significantly correlated with pH in lined canals. Fecal indicators (E. coli) did not predict pathogen (Salmonella) presence. Molecular methods (qPCR) suggested far higher levels of Salmonella when compared to cultural methods, with molecular markers for Salmonella exceeding culturing by more than 600%. The results of this work suggest that growers should exercise caution when irrigating after canal maintenance events, and to be completely certain of acceptable irrigation water quality, should wait for 48 hours following the onset of maintenance (typically 24 hours following the re-introduction of water to the channels) prior to irrigating crops. Further, irrigation district guidelines may consider: 1) disposing of the“first flush”of canal water following maintenance into nearby open areas, rather than sending poor-quality water into the irrigation canal system; 2) collect sediments and algae deposited on canal banks and transport to a secondary location to prevent precipitation runoff and re-introduction of bacteria-laden sediments to canals, and 3) consider the long-term costs and benefits of canal lining.

Nordre älv är ett av två utflöden från Sveriges största vattendrag Göta älv. Estuariet som består av älvens mynning och en del av skärgården, är speciellt med blandning av sött och salt vatten och är utpekat till bland annat Natura 2000-område. I framtiden är det ett möjligt scenario att flytta delar av sjötrafiken som idag går i Göta älv genom Göteborg, till Nordre älv istället. Förutsättningarna för sjötrafiken genom Göteborg förändras i takt med att staden utvecklas och förväntade havsnivåhöjningar kan fordra större skyddsåtgärder för staden i framtiden. Här spelar både samhälls-, ekonomi- och miljöaspekter roll och en sammanvägning av konsekvenser behöver göras. Eftersom tröskelområdet i Nordre älvs mynning är mycket grunt behöver i så fall muddring utföras. Det är ett fysiskt ingrepp där bottensediment tas bort för att skapa en djupare ränna där fartyg kan passera. För ett sådant ingrepp krävs tillståndsansökan samt en miljökonsekvensbeskrivning som beskriver direkta och indirekta effekter på miljö och människa. Denna rapport är en förstudie med inspiration av miljökonsekvensbeskrivning där effekter av muddring i Nordre älvs estuarium studeras. Litteraturstudien bygger på publikationer från myndigheter och organisationer, vetenskapliga artiklar samt personlig kommunikation med berörda och sakkunniga.I estuariet finns ålgräsäng som är ett viktigt habitat för födosök och som barnkammare för många arter. Lax och öring vandrar upp genom älven för att leka och ål som är rödlistad förekommer i området. Den största effekten av muddringen är direkt borttagande av vegetation och fauna. Andra effekter som kan få stor påverkan är grumling (kortsiktigt) och förändrad hydrodynamik. Ålgräsets omfattning kommer minska men det är förhoppningsvis möjligt att genom kompensationsåtgärder öka ålgräsutbredningen utanför muddringsrännan och därigenom motverka negativ nettoeffekt. Stor tyngd bör läggas på val av tidpunkt. Under sommaren då fortplantning sker är ekosystemet mest känsligt mot störningar. Men genom god planering med åtgärder för att minska påverkan samt noga val av teknik och utrustning kan negativa miljöeffekter begränsas.För att kunna utvärdera miljöeffekterna i ett större perspektiv behöver ytterligare studier göras i och kring Göteborg för att utvärdera vilka positiva och negativa effekter som uppstår av att flytta sjöfarten och andra framtida projekt. / The Nordre älv estuary is the largest of its kind in Sweden with the typical fresh and salt water mix. It contains eelgrass which is an important habitat for many organisms as feeding ground and nursery area. The estuary is protected by several different directives, laws and conventions, such as: nature reserve and Natura 2000 according to the Habitats Directive and Birds Directive issued by the EU. Because of changed conditions for marine traffic through Gothenburg it may be necessary to relocate it to the river Nordre älv in the future. That would require a dredging since the river mouth contains a shallow threshold. An environmental impact assessment (EIA) is required as part of the permit application for dredging. This essay is a literature review inspired by EIA based on publications from agencies and organizations, research, scientific articles and personal communication with experts. The major effect of dredging is directly removal of vegetation and fauna. Other effects that may have significant impact is clouding (short term) and altered hydrodynamics. Eelgrass extent will decrease but might be offset by compensational measures. Through proper planning and precautions it’s possible to reduce negative environmental impacts.

Studies were conducted to broadly describe and understand the sediment benthos of a shallow-water coastal area (Aramoana Beach - Heyward Point - Blueskin Bay) near the entrance to Otago Harbour, a system largely representative for southeastern New Zealand. Benthic assemblages were examined in relation to gradients of wave exposure and disturbance, sediment type and bathymetry, and dredge-spoil disposal. Sediment and macrofaunal surveys in autumn and spring 2003 found little change in sediment texture gradients from historical studies and a lack of vertical stratification. Macrobenthic samples from spring produced significantly higher abundances of three numerically dominant phyla (Arthropoda, Annelida, and Mollusca) and higher taxon richness compared to autumn. Within water depths of 6-30 m, abundance, richness, and diversity increased with depth. Multivariate analyses identified similar assemblages among deeper sites, despite sediment textural differences, whereas distinct assemblages were found in the shallow portions of the three areas. Meiofaunal abundance patterns did not reflect those of macrofauna, possibly indicating greater vertical penetration of sediments in these hydrodynamic environments. Several new kinorhynch taxa were found. In a field manipulation, part of the Aramoana dredge-spoil dumpground was protected from spoil disposal for an extended period followed by experimental dumping of sandy and muddy spoil. Macrofaunal samples were collected before dumping and at nine sites < 119 d after disposal. Water velocities at the sediment-water interface were compared to a local sediment disturbance model. Dumpground samples were depauperate in individuals and taxa compared to an area protected from dumping for > 180 d. A drop in abundance and a dissimilar community coincided with muddy spoil, but fine sediments were dispersed within 26 d and macrofaunal assemblages recovered to the pre-existing state. Sandy spoil, while not altering native sediment textures, had a more prolonged impact due to transplantation of macrofauna from the dredged area that persisted for < 41 d after disposal. Side-scan sonar mapping indicated that the disposal footprint model used approximated the extent of sandy spoil impacts well, while local conditions spread muddy sediments beyond the initial impact site. A novel sediment profile imaging device was constructed that has many advantages over existing devices for spoil mound studies and habitat mapping: it is smaller, can be manually deployed from small boats, is cheaper, and can be modified to work in almost any soft sediment. Studies of one dominant taxon, the gastropod Zethalia zelandica, showed it was better able to survive sand burial than mud burial, did not vary in overall activity through a range of 5-14� C, and contributed a large proportion of biomass of its community. The spoil disposal strategy used does not appear as environmentally neutral as originally thought. Only muds are effectively dispersed whereas coarser sediments accumulate, affecting physical and biological benthic processes of a wider area. Two mitigation strategies were evaluated using a heuristic model. Reducing the disposal area and spreading mud disposal events over a longer time span may be an effective interim strategy. Overall, the studies will help guide management of the area.

Thesis (M.M.S.)--Memorial University of Newfoundland, 2001. / Includes bibliographical references (leaves 75-82).