Dissertations / Theses on the topic 'Effect of dredging'
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1
n, Hussin Wan Mohd Rauhan. "Measurement of changes in marine benthic ecosystem function following physical disturbance by dredging." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/2838.
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Measuring the impact of physical disturbance on macrofaunal communities and sediment composition is important given the increased demand for the exploitation and disturbance of marine ecosystems. The aim of the present investigation was to provide a comprehensive study about the extent to which the disturbance (especially aggregate dredging) may affect benthic ecosystem function. The first part of the thesis concerns a field investigation of the impacts of dredging on the benthic community and related ecosystem function which was measured by different approaches including traditional methods based on benthic community structure and a more novel approach based on the functional traits of benthic organisms. The assessment was done by comparing dredged sites (Area 222, southeast England) with nearby undisturbed reference sites from the years 2001 to 2004 and in 2007. In general, low dredging intensity did not appear to impose great impacts on the benthic community and related ecosystem function compared to the higher intensity activity. Most of the analyses suggested that the community at the high dredging intensity site had yet to recover at the end of this study period. Among many factors related to the recovery of the benthic community was sediment composition where gravel deposits appeared to support a faster biological recovery. Meanwhile, the recovery of species with specific traits, such as tube-building and filter feeding also indicate a faster recovery for the whole community. The experimental work to determine different impacts of Hediste diversicolor on its surrounding depending on its relative size is discussed in Appendix 1.
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Selden, Justin D. "The Effect of Dredging on Fish Communities in Agricultural Streams in Crawford, Sandusky and Seneca Counties of Ohio." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372421206.
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Tamuno, P. B. L. "Eco-livelihood assessment of inland river dredging : the Kolo and Otuoke creeks, Nigeria, a case study." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/2334.
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Conventionally environmental assessments (EAs) have been carried out to enhance the understanding of the environment and for the purpose of developing appropriate environmental management and protection strategies. There are, however, limitations to the application of traditional EA approaches, particularly in rural communities in the developing world, where livelihood is dependent on common pool resources (CPRs), and baseline data are inadequate or unavailable. Eco-livelihood assessment (EcLA) is an adaptive approach that integrates a people focused sustainable livelihood approach with ecological assessment, as well as exploring traditional eco-livelihood knowledge (TELK). EcLA is identified as a promising EA tool that could help environmental professionals in planning for equitable development. This approach has been used in the Kolo and Otuoke Creeks, Niger Delta, Nigeria to investigate the ecological impact of dredging that may impact on livelihoods in such a rural setting. Ecological and social surveys have been carried out in four communities in the Study Area; two Test communities and two Reference communities (two communities from each study creek). The information collected from the social survey includes TELK, and has been used to build up a baseline scenario of the Study Area. Abundance and diversity of fish are good indicators of the eco-livelihood impacts of inland river dredging. The research shows that livelihood characteristics, river use profile, fish species diversity and abundance are very similar among all four sample communities. In addition, all sample communities have been associated with similar natural and human induced environmental consequences except that the Test communities have had river sections dredged for the purpose of land reclamation representing the baseline scenario. The analysis of the results of the ecological survey shows a difference in fish catch per unit effort, catch per unit hour, and species diversity between the Test and Reference communities, this have been attributed to the impacts of inland river dredging. The study shows that TELK has a place in environmental assessment, and that eco-livelihood assessment is one promising environmental assessment approach that could be used in areas where livelihood is strongly dependent on common pool resources.
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Knight, Peter David, and n/a. "Where did we go wrong? : a critical assessment of management in the Bluff Oyster Fishery." University of Otago. School of Surveying, 2008. http://adt.otago.ac.nz./public/adt-NZDU20081218.160813.
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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.
5
Croft, Alex. "The effects of thin layer dredge material disposal on tidal marsh processes, Masonboro Island, NC /." Electronic version (PDF), 2003. http://dl.uncw.edu/etd/2003/crofta/alexcroft.html.
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Milburn, Elizabeth Anne. "The effects of dredging on dissolved oxygen in agricultural waterways in King County, Washington." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Spring2007/E_Milburn_030907.pdf.
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MacDonald, David Simpson. "Ecological studies on the effects of scallop dredging on the benthos of the North Irish Sea." Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333574.
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Barber, Michael R. "Effects of Hydraulic Dredging and Vessel Operation on Atlantic Sturgeon Behavior in a Large Coastal River." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4792.
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The tidal James River, a focus of VCU's Atlantic Sturgeon program, supports both commercial shipping and hydraulic dredging. These anthropogenic threats present documented but preventable sources of mortality to the endangered species. Using three separate VEMCO Positioning System (VPS) receiver arrays, spatial data of previously-tagged fish were collected. ArcGIS and Programita software were used to analyze fish spatial distributions in the presence and absence of potential threats, using additional data including automatic identification system (AIS) vessel locations, vessel passages compiled using camera footage, and dredge records provided by the US Army Corps of Engineers. The data showed a change in distribution associated with vessels that varied according to river width but not vessel type. Dredging was associated with differences in spatial distribution, but more clearly for adults than sub-adults. The responses of Atlantic Sturgeon provide information necessary to propose potential threat mitigations, including seasonal restrictions for both vessels and dredging.
9
Morris, Stephanie M. "Effects of Dredging-Induced Sedimentation and Turbidity on Two Species of Stony Corals of Southeast Florida." NSUWorks, 1993. http://nsuworks.nova.edu/occ_stuetd/351.
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Sedimentation parameters, turbidity, extension (linear) growth, bleaching and polyp expansion were examined prior to, during, and after the dredge and fill activities associated with the first renourishment of Hollywood and Hallandale beaches, 1991. During the project, approximately 1.1 million cubic yards of beach compatible material was taken from two offshore borrow areas and placed on 5.3 miles of beach. Treatment stations were at offshore (adjacent to the borrow area) and nearshore (adjacent to fill area) locations. Control stations were placed at least 3km north, offshore of John U. Lloyd Beach State Recreation Area. Two coral species abundant in this area, Solenastrea bournoni and Dichocoenia stokesii, were monitored monthly on each reef for signs of bleaching and polyp expansion, indicators of stress and surface clearing ability respectively. After dredging was completed, the corals were collected for growth analysis (linear extension) by the Alizarin stain method. At treatment stations, associated with dredging, a significant decrease in extension growth rate in S. bournoni but not D. stokesii occurred. A decrease in fossa length of D. stokesii suggested that dredging effects caused a change in columella shape. Bleaching occurred in many of the colonies but may have been caused by an unknown factor. Polyp expansion, a means of sediment rejection, did not correlate with the proximity to dredging. The corals may be relying on other means of sediment removal. This study suggests that the effects of dredging on stony corals are species specific.
10
Avila, Christian L. "Effects Associated with Dredging for Beach Renourishments on Reef Fish Communities Offshore of Miami-Dade County, Florida:." NSUWorks, 2006. http://nsuworks.nova.edu/occ_stuetd/251.
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Beach erosion is an ongoing problem in South Florida. Beach replenishment has been the primary means of maintaining these economically important beaches, and dredging offshore sand deposits, adjacent to reef tracts, has been the pervasive method since the 1970's. Over the past ten years, greater attention has been paid to potential impacts dredging can have on adjacent reef communities, which has led to increased monitoring efforts. With the increase in monitoring efforts, scope has expanded from a strict focus on the benthic community to include the fish communities. This study evaluates the effects of dredging on reef fish communities associated with two separate beach replenishment projects, offshore of Miami-Dade County, Florida, U.S.A. Monitoring programs were developed and conducted by the Miami-Dade, Department of Environmental Resources Management (DERM). Monitoring took place between March 1997 and September 2000, with one project in northern portion of the county, off offshore of Golden Beach, and the other in the southern portion offshore of Key Biscayne. Both monitoring programs employed a Before After Control Impact design, with established test and control reef stations. Eight reef fish visual point count censuses (Bohnsack and Bannerot, 1986) were performed at each station prior to dredging, immediately following dredging, and three periods at bi-quarterly intervals after that.
In general evaluations of both project,s showed no indications that dredging activities had major impacts on the fish communities of adjacent reefs. For the Golden Beach project, there was one aspect of the analysis, which may be indicative of dredging related impacts; was species richness at one test station declined significantly following dredging activities (ANOVA p=0.047). However, in terms of abundance, diversity and Multidimensional scaling (MDS) plots of the Bray-Curtis dissimilarity index did not indicate that dredging activities impacted the test station. During the monitoring period of the Key Biscayne project, the south Florida region was impacted by two tropical storm events, which obscures the isolation of impacts associated with dredging. Changes in the reef fish communities, consistent with the impact and recovery of the tropical storms are evident in species richness, abundance, and MDS plots of the Bray-Curtis dissimilarity index, at both the test and control stations.
11
Panasik, Gina M. "Effects of the addition of dredged sediment to a marsh ecosystem on benthic microalgal biomass /." Electronic version (PDF), 2003. http://dl.uncw.edu/etd/2003/panasikg/ginapanasik.html.
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Obergh, Victoria Lee. "Canal Maintenance Effects on Irrigation Water Quality." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/582373.
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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.
13
Adda, Michele. "Possible ecological effects of continuous hydraulic sediment removal as an alternative to dredging at a small port entrance (Cervia, northern Adriatic Sea)." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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Siltation and sediment accumulation is a problem that affects many ports and harbours worldwide. Usually, dredging is the most common technique to handle this issue, but nowadays there is increasing concern about its several effects and impacts to the marine environment, especially referred to benthic communities, so that the need to find sustainable alternatives is becoming a topic of wide interest. One of these possible alternatives is represented by the so-called sand by-passing plants. In this study, the potential ecological effects of a new sand by-passing plant, called ejectors plant, have been investigated through a before-after control-impact design (beyond-BACI). The plant was installed in the proximity of the port inlet of Cervia, a small municipality situated in Emilia-Romagna, on the northern Adriatic coast. For the study, 3 different sampling periods (one before and two after plant installation) and 5 different sampling locations (one impact and four control locations) were established. The analysis has evaluated the sediments organic matter percentages and grain size classes composition, the shell debris weight, the structure of benthic communities and fish assemblages. PCO analysis and DistLM were performed to evaluate similarity between benthic communities and to find taxa and environmental variables most correlated with macrofaunal patterns. Moreover, a literature analysis about impacts of dredging on benthic communities have been performed. All results indicate that in last sampling period, 2nd after plant installation, the two possibly affected areas (sand pickup and deposit areas, respectively) values were more similar to control ones than before, suggesting that the ejectors plant could represent an eco-friendly solution alternative to dredging for harbour siltation problems. This work is part of the LIFE15 MARINAPLAN PLUS project, which had the aim of testing the efficiency and sustainability of the ejectors plant at industrial scale.
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Robbins, Jena. "Effects of ocean warming, sedimentation, and parental genotype on the post-settlement survival and growth of Acropora cervicornis recruits." Thesis, NSUWorks, 2018. https://nsuworks.nova.edu/occ_stuetd/483.
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Ocean warming and increased sedimentation from coastal activities are major threats to coral persistence. This study assessed the effects of increased temperature and sedimentation on the survival and growth of Acropora cervicornisrecruits. The potential for adults from different regions and genotypes to confer their offspring with higher or lower tolerance to heat and/or sediment was also determined. Gametes were collected and brought to the laboratory for cross fertilization of different genotypes within the regions collected. Larval rearing and settlement were then performed in the laboratory. Newly settled recruits were reared at 29 and 31°C (current summer temperature for August 2017 and +2°C as predicted for 2050) and 4 deposited sediment levels and turbidity (0, 30, 60, and 120mg cm-2, corresponding to 0, 4.52-5.35, 8.16-9.7, and 18.53-19.4 NTU). Recruit survival and growth were measured weekly for 3 months. Increased temperature reduced survival, suggesting faster usage of energy reserves. Regardless of temperature, survival was maximized under 30mg cm-2sediment; the highest sediment level drastically reduced survival. Increasing temperature by 2°C was as deleterious as doubling the natural level of deposited anthropogenic sediment, suggesting that eliminating local stressors may allow recruits to better sustain ocean warming. Growth was not affected by temperature nor sedimentation. Recruits produced by parents from the Florida Keys had a lower initial size but higher growth rate than those from Broward County. None of the parental genotypes conferred their offspring with higher or lower tolerance to warming and/or sedimentation. Reducing turbidity to 4.52-5.35 NTU or less during coastal construction may facilitate the persistence of this species by reducing recruit mortality the first 3 months post-settlement.
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Stephenson, Morgan. "Effects of deposited sediment and turbidity on survival and growth of Orbicella faveolata recruits." Thesis, NSUWorks, 2019. https://nsuworks.nova.edu/occ_stuetd/509.
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Corals are frequently exposed to elevated turbidity and deposited sediment caused from coastal construction, dredging, and/or beach renourishment. This study addresses the effects of turbidity and deposited sediment on the survival and growth of newly settled and 6-week-old Orbicella faveolata recruits and disentangles the effects of turbidity and deposited sediment. We conducted two experiments in which newly settled coral recruits were reared in one of ten different turbidity and deposited sediment treatments for five weeks (0 NTU/ 0 mg cm-2, 3.4 NTU/ 0 mg cm-2, 8.2 NTU/ 0 mg cm-2, 16 NTU/ 0 mg cm-2, 29.1 NTU/ 0 mg cm-2, 0 NTU/ 0 mg cm-2, 3.4 NTU/ 27.7 mg cm-2, 8.2 NTU/ 50 mg cm-2, 16 NTU/ 101 mg cm-2, 29.1 NTU/ 220 mg cm-2). The highest turbidity treatment in the absence of deposited sediment (29.1 NTU/ 0 mg cm-2) had the best survival, suggesting that turbidity in the absence of sediment is beneficial to coral recruits, as it decreases harmful light levels. However, when recruits were exposed to both turbidity and deposited sediment, representative of normal coastal construction conditions, high turbidity when coupled with deposited sediment (16 NTU/ 101 mg cm-2 and 29.1 NTU/ 220 mg cm-2) had negative effects on coral recruits. Based on the results from the first experiment, the experiment was repeated with six-week-old symbiotic recruits for two weeks to determine if the sensitivity to light and benefits of high turbidity were related to the presence of symbionts. Six-week-old recruits also had the highest survival in the highest turbidity treatment, suggesting that light sensitivity by coral recruits is not dependent on the presence of symbionts within the first six weeks post-settlement. While the low light associated with turbidity increases recruit survival, turbidity is a proxy for deposited sediment, which has negative effects on coral recruits. Based on the results from this study, regulations should prevent turbidity from exceeding 8.2 NTU to prevent excessive deposited sediment on coral reefs, and its deleterious effects on corals.
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Paavo, Brian Lee, and n/a. "Soft-sediment benthos of Aramoana and Blueskin Bay (Otago, New Zealand) and effects of dredge-spoil disposal." University of Otago. Department of Marine Science, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070928.161657.
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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.
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WeiKao and 高瑋. "Effect of Dredging on Reduction in River Flood Stages." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/45svhd.
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碩士國立成功大學
水利及海洋工程學系
106
In Taiwan, hillslides are of the geological and topographical conditions that are unfavorable to slope stability, thus readily leading to soil-stone collapse due to earthquake and rainfall, further forming loose rock deposition area and colluvium. Heavy rain runoff will erode and transport the rock into the channel, affecting the balance of the sediment transport and channel stability. With a large amount of rock flowing into the upstream, the midstream and downstream will have river deposition issues due to insufficient sediment transport capacity. As a result, the flood discharge section will be reduced and the flood stage will rise. This will endanger flood-control structures as well as the life and property of the residents on field sides of the levee. Dredging riverbed sedimentation to harness the channel and to increase the flood discharge section is one of engineering methods used to reduce flood stages. Moreover, it will prevent flooding and maintain the stability of the riverbed. The study is aimed toward an investigation of the use of dredging methods on reducing flood stages to prevent overflow and to maintain the stability of the riverbeds. This study simulates an alluvial river flood process using the two-dimensional hydraulic and sediment transport model. Based on the comparison of current channel and the flood stages of different dredging schemes, the effectiveness of dredging on reducing the flood stage is evaluated, a result that can be used as a reference for the selection of dredging schemes. The Gaoping River watershed is prone to large-scale landslides when heavy rains or typhoons occur, the deposition often cause occasional flooding of downstream, affecting the Gaoping River Weir water usage. Therefore, it is proposed that using the dredging method to reduce the flood stage will improve upstream deposition situation and be useful to the Gaoping Weir water intake. The present study investigated dredging methods on the upstream of the Gaoping River Weir, selecting four types of dredging schemes within the dredging area that locates on the convex bank of the main channel. A two-dimensional hydraulic sediment transport model was used to calculate the flood stage along the river, and the flood stage before dredging was taken as the basis for the comparison of effectiveness. The simulation results showed that the dredging method lengthened and widened the dredging area, and thus effectively reduced the flood stage. Because of the improvement in sediment storage, the dredging area can reduce the downstream deposition and strengthen the levee and revetment.
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Kang, Chiao-Yin, and 康喬茵. "Effect of reservoir dredging on the water qualities of Zengwen River." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/fj6k98.
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碩士國立屏東科技大學
環境工程與科學系所
106
This study focuses on Zengwen Basin, and tries to analyze the water quality monitoring data of the Environmental Protection Administration Executive Yuan from 2011 to 2017. The study tries to figure out the trend of water quality changes in the dredging from the upstream reservoir in the Zengwen Basin. The study focuses on suspended solids and uses methods such as box-and-whisker plot analysis, WQI7 water quality index analysis, and qualification rate analysis. Analyzing the WQI7 index values of water quality monitoring stations from 2011 to 2017, the most water quality stations still maintain the same surface water classification standards. But from 2013 to 2017, the concentration of suspended solid has rose, and qualification rate of suspended solid has dropped, this suggests that the effect of the dredging from the upstream reservoir in the Zengwen Basin. Because dredging operations use typhoon and heavy rain to discharge muddy sand into rivers, which in turn affects river turbidity and suspended solids concentration. Statistics the WQI7 of Zengwenxi Bridge, and the proportion of Category C water bodies is 62.7%. The current classification of surface waters has designated Zengwenxi Bridge as Category B water bodies, so it is recommended to adjust the water body classification of Zengwenxi Bridge.
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Li, Chieh-Ting, and 李玠廷. "The Effect of Torrent Dredging on Bed Scouring and Deposition of Upstream Watershed." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/63243817315023490120.
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碩士逢甲大學
水利工程與資源保育學系
102
The study was conducted for the evolution of river sediment erosion and deposition process studies, conducted by CCHE1D torrent Mei River the erosion simulation, the model verification and validation, and to consider the anti-dam sediment under the regulation of the amount of outflow, three scenarios were simulated scenarios, the ultimate goal of proposed dredging to what extent, with the project management, the relevance of sediment erosion control facilities between change and conservation, let river erosion, siltation restore balance. The results can be summarized as following. 1. The sand sediment dam on the ability to regulate the outflow line to the flood conditions under single market estimate, As calculated at an annual three games torrent, It can adjust the amount of sediment outflow is obviously much higher than the amount of storage and production inhibiting amount of sand, Therefore, the amount of sand dam sediment mainly from the period of adjustment torrent, its value is far greater than the amount of storage and production inhibiting amount of sand. 2. Three programs explore the sand from the sand dam efficiency, In the river under the same amount of sediment inflow conditions, the less amount of sediment flow, the higher the efficiency of sand dam. 3. Simulation results show that the program, The program did not improve in the river erosion cut the circumstances presented, for the threat that already exists on both sides of the river; while improving the anti-dam after dam changed by adjusting the amount of sediment flow simulation results show that the original Nan Fung bridge upstream segment scour, erosion depth was significantly less than the program did not improve scour depth.
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Uchino, Kanako. "Long-term ecological impacts of dredging on coral reefs in Kaneohe Bay, Oahu." Thesis, 2004. http://hdl.handle.net/10125/11619.
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Weng, Tso-Hsin, and 翁作欣. "The Effect of Sediment Deposition Potential Due to Dredging-A Case Study of Laonong River Upstream." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/57835779888158125780.
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碩士國立屏東科技大學
土木工程系所
97
In river management, to ensure the flood discharge capability or protect the bridge, the application of dredging at appropriate place may reduce sedimentation and increase flood protection potential with a short term effect. Thus, it is interesting to explore the sediment deposition potential and its effects due to dredging. By using NETSTARS to simulate sediment transport, this research aims to explore the deposition and the change of hydraulics after dredging. Also, the related issues regarding the change of hydraulic of channel and riverbed elevation by dredging under the ideal conditions are also discussed. This research mainly focuses on the simulation of sediment transport in Laonong River, and the investigation of the change in hydraulics and sedimentation from the historical flood series to explore the tendency of hydraulic and sediment transport after dredging. From the results of this research, it reveals the river channel will continuously maintain as sediment deposition status while the reiver management remains the same as present. And, the study also reveals the main sediment deposition section is in upper stream. The simulation results show that the total sediment deposition varies much in different dredging proposals, however the change in upper stream is more stable, although it is the main sediment deposition section. The variance of sediment deposition is mainly affected by the change of middle, down stream, while mostly from down stream. Therefore, dredging is more effective to down stream, and has little influence to upper stream in terms of sedimentation quantity.
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Perez, Diana H. "Effects of a 4-inch suction dredge on benthic macroinvertebrates in southwestern Oregon." Thesis, 1999. http://hdl.handle.net/1957/33160.
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Effects of 4-inch (10.16 cm) suction dredge mining on benthic macroinvertebrates in 3rd to 4th order streams were investigated in 1996 by evaluating four mining claim operations in Althouse Creek, Sucker Creek, and Taylor Creek in southwestern Oregon's Rogue River basin. The effects were site-specific. The study showed no significant (p>0.05) differences between treatment and control areas in density and species diversity of benthic macroinvertebrates. However, mean taxa richness significantly (p<0.05) increased thirty days following the end of the mining period. Collector-filterers were significantly (p<0.05) lower in dredged areas thirty days after the mining season. Because of constraints in sampling design, sample sizes and relatively small treatment areas, the results from this study are tenuous at best. There were apparent inherent differences in species dominance among sites possibly a result of differences in stream size and riparian conditions. This further confounds results of this study.Graduation date: 2000
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Decker, Christopher Dylan. "The effects of sand dredging on the aquatic macroinvertebrate community in two urban piedmont streams." 2002. http://purl.galileo.usg.edu/uga%5Fetd/decker%5Fchris%5Fd%5F200212%5Fms.
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