Дисертації з теми "Floodplain sediments"
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1
Denys, Frank. "Transverse transport of suspended sediment across the main channel - floodplain shear boundary /." Link to the online version, 2007. http://hdl.handle.net/10019/415.
2
Denys, Frank. "Transverse transport of suspended sediment across the main channel – floodplain shear boundary." Thesis, Stellenbosch : University of Stellenbosch, 2006. http://hdl.handle.net/10019.1/2602.
Анотація:
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006.The floodplain of a river forms a close relationship with the stream that created it. Not only does the river influence the characteristics of the floodplain, the floodplain can also very easily influence its river, as is evidenced by examples such as the Huang He River in China and the Columbia River in Canada. These two cases clearly indicate that suspended sediment has a pronounced influence on the floodplain. This thesis investigates the processes which cause sediment to move onto the floodplain. As observed in many rivers worldwide suspended sediment on the floodplain has a tendency to settle near but not directly next to the main river channel. This gap between the river channel and the location of highest sedimentation rate stems from the fact that there is a zone of relatively higher turbulence at the boundaries of the floodplain. Close to this zone flow on the floodplain is increased in velocity whilst the flow velocity in the main channel is decreased as can be seen in the figure below: ...
3
Zhao, Yingkui. "Heavy metal distribution in floodplain sediments of the river Severn, UK." Thesis, University of the West of England, Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327475.
4
He, Qingping. "Interpretation of fallout radionuclide profiles in sediments from lake and floodplain environments." Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358000.
5
Alderson, Danielle. "The fate of carbon in upland floodplain sediments : a combined geomorphological and organic geochemical approach." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/the-fate-of-carbon-in-upland-floodplain-sediments-a-combined-geomorphological-and-organic-geochemical-approach(fb0b0de9-6906-4000-9d1d-897c382ca479).html.
Анотація:
As conveyors of water and sediment, rivers play an instrumental role in landscape evolution (Turner et al., 2015). River systems were traditionally considered as passive pipes of terrestrial organic carbon (OC), but are now viewed as active sites of OC processing, redistribution and storage (Aufdenkampe et al., 2011). Floodplains are an important part of this system and have the capacity to act as sources or sinks of carbon (Zehetner et al., 2009), but most importantly active hotspots of organic matter (OM) transformation (Hoffmann et al., 2009; Zocatelli et al., 2013). POC eroded from highly-organic peat soils, may be interrupted in its transport through the fluvial system, by temporary storage on floodplain landforms (Evans and Warburton, 2005; Evans et al., 2006). It is important to investigate the fate of fluvial peatland POC, in order to fully close the terrestrial peatland carbon budget, to account for subsequent mineralisation and explore the processes that lead to redistribution and storage. The River Ashop in the southern Pennines, UK, drains the slopes of both Bleaklow and Kinder Scout which are upland plateaux, which support an extensive cover of blanket peat (Evans and Lindsay, 2010). These peatlands have been severely eroded and are vulnerable to future erosion as they are marginal to the climatic space suitable for growth of peat bogs in the UK (Clark et al., 2010). The wider peatland catchment features cohesive, organic-rich floodplains, which are atypical in an upland landscape, and thus suitable for investigation in their role in the fate of eroded carbon. OM quality was an important focus of this research into the redistribution of terrestrial organic carbon. As such, OM quality was conceptualised, by identifying how different research disciplines identify with the term, and ultimately providing a classification scheme to assist individuals in their exploration of OM character. A novel approach using ITRAX core scanning data was used to establish carbon stocks of floodplains in the River Ashop catchment. Sedimentological characteristics were insufficient to distinguish between allochthonous and autochthonous organic matter storage. However, dating was used as a rapid and accurate tool to assess carbon source on the 'off-site' floodplain, and could perhaps be used in the wider environment where there are large discrepancies between the ages of source materials. Investigations into the OM quality, provided suitably convincing evidence that substantial overbank deposition of eroded 'old' peat had occurred. Despite this, viewing these sites simply as areas of carbon storage is misleading. In fact, these systems have potentially been turning over substantial quantities of carbon to the atmosphere. Contextual information from modern-day fluvial POC fluxes showed that both 'off-site' and 'on-site' floodplains only play a minor role in storing carbon. Geomorphological events, particularly the substantial sediment flux generated from peatland erosion were critical in the formation of these floodplains. In these peatland systems, erosion, deposition and turnover of carbon are intimately linked at the landscape scale, and floodplains are a dynamic component of this system.
6
Vandeberg, Gregory Scott. "The distribution of trace elements in floodplain soils and sediments of the upper Blackfoot River, Montana /." Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
7
Michel, James T. Helfield James M. "Seed rain and selected species germination and growth trials : implications for natural and augmented revegetation of post-dam Elwha River floodplain and reservoir sediments /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=361&CISOBOX=1&REC=5.
8
Bechtold, James Scott. "Fluvial sediment influences on floodplain soil biogeochemistry /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/5358.
9
Euzen, Cassandra. "Reconstruction spatio-temporelle des dépôts métalliques le long d'un hydrosystème fluvial fortement anthropisé : combinaison d'approches géochimiques, hydrogéomorphologiques et géochronologiques appliquée au Rhin supérieur." Electronic Thesis or Diss., Strasbourg, 2023. http://www.theses.fr/2023STRAH006.
Анотація:
Connaitre l'évolution temporelle de la composition chimique des rivières fortement anthropisées est essentiel pour évaluer l'impact des activités humaines et des mesures de réduction de la pollution. La plupart des contaminants s'associant aux sédiments fins, l'analyse géochimique de dépôts sédimentaires bien datés formés dans les plaines inondables peut permettre de reconstruire la trajectoire des fleuves sur plus d’un siècle. Dans ce cadre, cette thèse a eu pour objectif de reconstruire, à partir d’archives sédimentaires, l’évolution des émissions humaines en métaux dans le Rhin supérieur. Plus précisément, une première partie s’est intéressée à la datation robuste et précise des sédiments déposés durant les 200 dernières années à partir d’une analyse multiméthodes (anciennes cartes, hydrologie, datation par luminescence, 137Cs, 210Pbxs). Une séquence sédimentaire longue et continue a ensuite été étudiée pour reconstruire les impacts humains historiques en métaux sur le Rhin. Enfin, la variabilité spatiale de l’enregistrement des contaminations historique a été étudiée entre Bâle et Strasbourg grâce à plusieurs archives sédimentairesUnderstanding the temporal evolution of the geochemical composition of heavily impacted rivers is crucial for assessing the impact of human activities and measures to reduce river pollution. To this end and since most contaminants are associated with suspended load, geochemical analysis of well-dated floodplain sedimentary deposits can allow reconstructing the chemical trajectory of rivers over a century or more. This thesis aimed to reconstruct the historical metal emissions in the Rhine by studying its sedimentary archives. Specifically, the first part of the work focused on robust and precise dating of sediments deposited during the last 200 years using a combination of historical planimetric (old maps) and hydrological data with geochronological dating (single grain IRSL, 137Cs, 210Pbxs). Subsequently, the work focused on a long and continuous sedimentary sequence to reconstruct historical metal emissions in the Rhine. Finally, the spatial variability of the historical contamination record was studied between Basel and Strasbourg using several sedimentary archives
10
Ahmed, Joshua. "Sediment-triggered migration and floodplain habitat development in meandering rivers." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/105765/.
Анотація:
Meandering rivers create some of the most intricate and diverse regions on the planet. Lateral migration excavates floodplain material from the outer banks of meanders and subsequently deposits it at the hydrodynamically calmer inner bank region, creating point bars. Point bars are constructed by the progressive attachment of sediment in the form of scroll bar deposits: sediment shoals up and becomes deposited on the margins of the bar, increasing its aerial extent, which becomes stabilised by vegetation once regular inundation ceases. Point bars have the potential to affect flow as it is routed through the meander by both increasing the curvature of the bend and topographically forcing water to flow outwards, increasing boundary shear stress and rates of bank erosion. A combination of remotely-sensed data, GIS, and a 2D morphodynamic flow model was used to examine the role of externally-imposed sediment supply on point bar growth and floodplain evolution in the Amazon Basin. Externally-derived sediment supply is important since it provides the material used to build point bars – of course supplemented by internal sediment sources. A simulated reach on the Sacramento River, USA was used to investigate the role of increased sediment supply on bar growth and meander evolution through time. It is demonstrated that rivers characterised by high sediment loads have greter migration rates, rates of cutoff production, and larger populations of oxbow lakes driven by the maintenance of a steady-state sinuosity on the rivers through time. Channel sinuosity increases with migration rate, although the rate of sinuosity increase is determined by the type of meander deformation: downstream translating bends increase their length more quickly than their upstream translating or extensional counterparts. Point bar growth was observed to occur under high sediment loading conditions when modelled using a 2D morphodynamic model. The bar sequestered sediment at the upstream head of the bar causing it to grow ii upstream. This increased the distance of outer bank subjected to bank erosion and also increased to magnitude of bank erosion. a sediment-driven control on sinuosity increases manifested through bend deformation style, and the simulated growth of point bars in the presence of enhanced sediment loading which resulted in increased rates of bank erosion. These results are of significance for meandering theory and particularly indicate the importance of point bars in effecting the morphodynamic evolution of meandering rivers.
11
Blake, William Henry. "The use of â·Be as a tracer in sediment budget investigations." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324133.
12
Stone, Peter Michael. "The particle size selectivity of suspended sediment delivery from drainage basins." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337807.
Анотація:
The delivery of suspended sediment from drainage basins has frequently been quantified in mass terms by use of the suspended sediment budget approach, which identifies sources, storage and output of mobilised sediment. This thesis investigates the particle size characteristics of the sediment associated with the key components of the suspended sediment budgets of four drainage basins in Devon, U. K. to determine whether particle size selectivity occurs in the delivery of suspended sediment from the hillslopes to the basin outlet. Attention focused on pasture land because previous studies had indicated that this was the dominant source of suspended sediment and that arable fields and channel banks were relatively insignificant in these catchments. Samples of sediment were mobilised from pasture hillslopes using a field-portable rainfall simulator; samples of suspended sediment were collected from the river channel during storm events either manually, by automatic pump samplers or by using rising limb siphon samplers; suspended sediment deposited on the channel bed was sampled using bed traps and by resuspending sediment deposited on the river bed during low flows; and sediment deposited on the floodplain during overbank flooding was collected using Astroturf mat traps or by sampling surface material. Samples were collected to investigate both temporal and spatial variability in grain size behaviour. All sediment samples were pretreated to remove organic matter and their chemically dispersed (absolute) particle size composition was measured using a Coulter LS 130 laser granulometer. The particle size composition of transported/deposited sediment was compared with that of the samples from potential sources to determine whether particle size selectivity had occurred. Where possible, measurements of the natural in situ particle size distribution (effective particle size) were also undertaken by quick return of samples to the laboratory for immediate measurement without pre-treatment using the laser granulometer. Particle size selectivity was found to have occurred in the mobilisation of sediment from the hillslope pasture land sources. Seasonal variations were identified in the particle size characteristics of both sediment mobilised from the hillslopes and suspended sediment samples. Spatial variations were identified in the particle size composition of sediment deposited on the floodplain. These seasonal and spatial variations reflect the particle size selectivity of detachment, transport and deposition processes which is in turn influenced by the aggregation or flocculation (effective particle size) of the sediment.
13
Jung, Kwansue 1959. "The comparative sediment processes in channel and overbank." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277205.
Анотація:
The question posed in this study is why alluvial soil on a floodplain is finer than the bed material of the river that supplied the sediments deposited to form the floodplain. A schematic, simplified river/floodplain system is used in an approximate analysis to find the size distribution of the floodplain soil. It is assumed that the stable limiting condition is a suspended load in the floodplain flow of the same concentration and composition as the sediment load in that portion of the river channel flow above the level of the floodplain. It was found that floodplain soil should be finer than the channel bed material; how much finer depending on the bank height, and to a lesser degree the width of the floodplain.
14
Souffront, Alcantara Michael A. "Channel Adjustment and Channel-Floodplain Sediment Exchange in the Root River, Southeastern Minnesota." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/3334.
Анотація:
A better understanding of transport and deposition of fine sediment in alluvial rivers, including their floodplains, is essential for improved understanding of sediment budgets and prediction of river morphological changes. Previous work in the Root River indicates that channel-floodplain sediment exchange exerts strong control on the sediment flux of this system. In addition, improvements in agricultural practices and increases in high and low flows during the past five decades have led us to believe that sediment sources in the Root River may be shifting from uplands to near-channel sources. This thesis estimated the total amount of fine sediment contributed to the channel from near-channel sources due to the processes of lateral channel adjustment (channel migration and channel widening) using a quantitative approach based on the use of multiple epochs of aerial photographs (1930s-2010s), lidar data available for the entire watershed from 2008, and other GIS analysis. The results obtained in this thesis serve as another line of evidence to constrain a sediment budget for the Root River watershed and to improve our understanding of the sediment dynamics within the watershed. In addition, we found that the Root River presents a marked division between its lateral channel adjustment trends before and after the 1970s. We also found that while increases in flows have affected lateral channel adjustment rates throughout the entire channel network, other factors like sediment supply and riparian vegetation may be playing an equally important role.
15
Brooker, Michael R. "Physical and Chemical Characterization of Self-Developing Agricultural Floodplains." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1513778530623727.
16
Cooper, Dylan Morgan. "Nutrient release potential during floodplain reconnection: Comparison of conventional and ecological stream restoration approaches." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/82487.
Анотація:
In the last few centuries, many streams in the eastern United States have been severely disturbed by land use change and are now disconnected from their original floodplain due to the aggradation of legacy sediment. Currently, stream-floodplain reconnection is advocated as a stream restoration practice to take advantage of ecosystem services. The objective of this study is to compare two current stream restoration approaches for their nutrient flushing ability: 1) a conventional approach leaves legacy sediment on the floodplain; and 2) an ecological approach that involves removing the accumulated legacy sediment in order to restore the original floodplain surface wetland, revealing a buried A soil horizon. Soil cores were taken from the surficial legacy sediment layer and the buried A soil horizon in the floodplain of a 550-meter reach of Stroubles Creek in the Valley and Ridge province near Blacksburg, VA, to evaluate potential for flushable DOC, TDN, NO3-, NH4+, and SRP content. In addition, an inundation model was developed to evaluate the extent of flooding under the two restoration scenarios. The inundation model results and nutrient flushability levels were then used to simulate the release of nutrients as a function of stream restoration approach. Results indicate that the buried A horizon contained less flushable nutrients, but the ecological restoration would have a higher frequency of inundation that allows for more flushable nutrient release at the annual scale. Understanding the nutrient release potential from the floodplain will provide the ability to estimate net nutrient retention in different stream-floodplain reconnection strategies.Master of Science
17
Benassi, Roseli Frederigi. "Dinâmica espaço-temporal de um sistema de áreas alagáveis na planície de inundação do rio Jacupiranguinha, Vale do Ribeira de Iguape, SP." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/18/18138/tde-26012007-101647/.
Анотація:
O objetivo principal deste estudo foi verificar a dinâmica espaço-temporal das variáveis limnológicas de um sistema de áreas alagáveis naturais, em microbacia no Vale do Ribeira de Iguape, rio Jacupiranguinha, sob influências de pulsos hidrológicos distintos, para inferir a capacidade destes sistemas em depurar e ou aprisionar carga de nutrientes potencialmente poluidoras que aportam nestas áreas. Para tanto, foram selecionados 11 pontos de amostragem: 1 e 2 no rio Jacupiranguinha; 3 no córrego Serrana; 4 a 10 no sistema de áreas alagáveis; e 11 saída do sistema, próximo ao rio Jacupiranguinha. Amostras de água foram coletadas em 4 períodos, em todas as estações de coleta, e determinadas as concentrações de nutrientes, DBO, DQO, coliformes fecais e totais. No sedimento foram determinadas as concentrações de nitrogênio total, fósforo total e matéria orgânica. Nas estações do sistema de áreas alagáveis foram coletadas macrófitas aquáticas. Medidas de temperatura, condutividade elétrica, pH, OD foram realizadas utilizando-se sonda multiparamétrica. Realizou-se um levantamento topográfico, estudo batimétrico na planície e foram instaladas réguas hidrométricas na área. As vazões e os níveis hidrométricos do rio Jacupiranguinha tiveram relação direta com a precipitação. As lagoas da planície não apresentam comunicação permanente com o rio, são necessários valores acima de 2,47 m para que ocorra o transbordamento e, consequentemente, a fertilização do sistema de áreas alagáveis. Com a utilização do software PULSO foram observados 5 e 3 pulsos completos, nas cotas topográficas 2,47 m e 2,97 m, respectivamente. A duração de ambas as fases dos pulsos (potamofase e limnofase) foram diferentes, a limnofase prevaleceu no período estudado. O regime de pulsos parece ter um efeito homogeinizador no sistema. Diferenças espaciais e sazonais foram observadas nas variáveis limnológicas da água. O sedimento não apresentou diferenças sazonais e espaciais significativas, entretanto, mostrou-se o compartimento de maior armazenamento de nitrogênio, fósforo e matéria orgânica nas estações das lagoas I e II. Números mais elevados de coliformes foram registrados nos pontos 1 e 2. As macrófitas aquáticas presentes no sistema de áreas alagáveis apresentaram importante participação na determinação dos padrões de ciclagem e aprisionamento de nitrogênio e fósforo total, pois estocam quantidades significativas destes nutrientes em sua biomassa. Em termos de reduções de cargas, no período seco, o sistema de áreas alagáveis apresentou reduções consideráveis levando em consideração a série nitrogenada, fosfatada e DBO. Assim, o regime de pulso mantém a conectividade do rio Jacupiranguinha com o sistema de áreas alagáveis e determinam a dinâmica dos fatores abióticos e bióticos, fundamentais para que esse sistema possa funcionar como armazenador e ou depurador de cargas poluidoras advindas deste rio. Entretanto, recomenda-se a construção de sistema de áreas alagáveis artificial para a complementação do tratamento de esgoto existente na área.The aim of this study was to verify the spatial and temporal dynamics of natural wetland limnological variables, in Jacupiranguinha river, a micro basin from Ribeira de Iguape Valley, under distinct hydrological pulses. This was made to infer these systems capacity in depurating or retaining potentially polluting nutrients in wetlands. It was selected 11 sample points: 1 and 2 in Jacupiranguinha river; 3 in Serranas brook; 4 to 10 in wetland system and 11 in the exit of the system, next to Jacupiranguinha river. Samples were collected in four different periods for nutrients determination, BOD, COD, fecal and total coliforms analysis. In sediment was determined nitrogen and phosphorus concentrations and organic matter. It was collected aquatic macrophytes too. Temperature, electric conductivity, pH and dissolved oxygen were measured with YSI probe. Topography was determined and a batimetric study was made in floodplain; besides, it was installed hydrometric rulers in the area. Discharge and hydrometric levels of Jacupiranguinha river were positively related with precipitation. The floodplain ponds were not permanently connected with fluvial course; it is necessary values above 2,47 meters to overflow the wetland and connect it with the river. With the software PULSO was observed 5 and 3 complete pulses, with respectively 2,47 m and 2,97 m of topographic level. Duration of pulse phases (potamophase and limnophase) was different, and limnophase had predominated. Pulse regime seems to homogenize the system. Seasonal and spatial differences were observed in water limnological variables. The differences in sediment were not significant; however it showed the higher nitrogen, phosphorus and organic matter concentrations in the two ponds. Higher coliform concentrations were registered in points 1 and 2. The aquatic macrophytes present in the studied wetland were very important in nitrogen and phosphorus cycle and retention of these nutrients in their biomass. In terms of load reduction, nitrogen, phosphorus and BOD were considerable reduced in dry season. Thus, pulse regime maintains the wetland connected with Jacupiranguinha river and guide the biotic and abiotic factors dynamics, very important factors for a better operation of the system, serving as nutrient storage and depurative. However, we recommend the construction of an artificial wetland system to complement the waste treatment in the studied area.
18
Remor, Marcelo Bevilacqua. "Geoquímica do sedimento do pantanal brasileiro." Universidade Estadual do Oeste do Parana, 2017. http://tede.unioeste.br:8080/tede/handle/tede/278.
Анотація:
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Previous issue date: 2017-02-17Floodplains have a high potential for nutrients transformation, however, when they accumulate at critical levels, generates an ecosystem degradation. The hydrological regime that controls nutrient dynamics in floodplains it is very responsive to changes in soil use and soil occupation or by changes climate pattern. In this context, this research aimed at reconstructing the history of nutrient accumulation and eutrophication of the Brazilian Pantanal, identifying the factors and/or phenomena that have influenced those variables. The sedimentation cores were collect in ponds that showed permanent connections to the main channel of Paraguai, São Lourenço and Cuiabá Rivers. The sediment cores were sliced in two-centimeter uniform intervals and quantification of total organic carbon and total nitrogen were carried out by readings in CNS elemental analyzer. Quantification of phosphorus was carried out by mass spectroscopy by inductively coupled plasma. The organic carbon in sediment of Brazilian Pantanal is mainly from allochthonous origin, being the nitrogen and phosphorus nutrients limiting of the productivity in the system, elements whose origins are agricultural practices in the drainage basin. The establishment of geochemical background is indispensable to determine the actual state of soils and sediments contamination. However, there is no scientific consensus about the methodology to determine those values. In this sense, this paper has established the geochemical background in Brazilian Pantanal sediments, based on the integrated method, in order to identify the appropriate calculation methodology for that region. The use of integrated methods, mainly the non-parametric statistics, has proved be useful in reliably determining geochemical reference values. Therefore, the authors recommend integrated methods to establish the geochemical background for others points in the Brazilian Pantanal.
As planícies aluviais apresentam elevado potencial de transformação dos nutrientes, entretanto, o seu acúmulo em níveis críticos gera a degradação do ecossistema. O regime hidrológico que controla a dinâmica de nutrientes nas planícies aluviais, é muito sensível às mudanças no uso e ocupação do solo ou por mudança no padrão climático. Nesse contexto, o presente estudo tem por objetivo reconstruir o histórico do acúmulo de nutrientes e da eutrofização do Pantanal brasileiro, identificando os fatores e/ou fenômenos que influenciaram essas variáveis. Perfis de sedimento foram coletados em lagoas com ligações permanentes ao curso principal dos rios Paraguai, São Lourenço e Cuiabá. Os perfis de sedimento foram fatiados em intervalos uniformes de dois centímetros e as quantificações do carbono orgânico total e nitrogênio total foram realizadas por leituras em analisador elementar CNS. A quantificação do fósforo foi realizada por espectrometria de massa por plasma acoplado indutivamente. Observou-se que o carbono orgânico total no sedimento do Pantanal brasileiro é principalmente de origem alóctone, sendo o nitrogênio e o fósforo os nutrientes limitantes da produtividade no sistema, cuja origem são as práticas agrícolas na bacia de drenagem. O estabelecimento de valores geoquímicos de referência é indispensável para determinar o real estado de contaminação dos solos e sedimentos. Entretanto, não existe consenso científico quanto à metodologia de determinação destes valores. Nesse sentido, esta pesquisa busca estabelecer os valores geoquímicos de referência dos sedimentos do Pantanal brasileiro a partir do método integrado, a fim de identificar a metodologia de cálculo mais apropriada para a região. A utilização dos métodos integrados, principalmente a utilização de estatística não paramétrica, demonstrou-se útil para determinar, de forma confiável, os valores geoquímicos de referência. Sendo assim, os autores recomendam o uso de métodos integrados para que se estabeleçam os valores geoquímicos de referência para outros pontos no Pantanal brasileiro
19
Jayakaran, Anand D. "The formation of benches in agricultural channels in Ohio." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149002547.
20
Hung, Nguyen Nghia [Verfasser], and András [Akademischer Betreuer] Bárdossy. "Sediment dynamics in the floodplain of the Mekong Delta, Vietnam / Nguyen Nghia Hung. Betreuer: András Bárdossy." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2012. http://d-nb.info/1021343994/34.
21
Southwell, Mark, and n/a. "Floodplains as dynamic mosaics : sediment and nutrient patches in a large lowland riverine landscape." University of Canberra. n/a, 2008. http://erl.canberra.edu.au./public/adt-AUC20081217.144116.
Анотація:
Rivers around the world are under increasing pressure from a variety of human activities.
Effective management of riverine landscapes requires an ecosystem approach and one that
recognises the complex interactions between their physical, chemical and biological
components. Perceptions of pattern and process are central to our understanding of riverine
landscapes. Pattern and process operate over multiple scales to produce heterogeneous
mosaics of landscape patches that change over time. Hierarchical patch dynamics provides a
useful approach to unravel pattern and process at multiple scales in riverine landscapes. This
thesis adopts a hierarchical patch dynamics approach to investigate floodplain sediment and
nutrient dynamics within the Barwon-Darling River in South Eastern Australia.
The flow regime of the Barwon-Darling River is highly variable. As a result, it has a complex
channel cross section featuring inset-floodplain surfaces that occur at multiple elevations
within the channel trough. These surfaces formed the focus of this study. The texture of inset- floodplain
surface sediments displays a patchy spatial distribution and one that did not reflect
lateral or longitudinal gradients within this floodplain landscape. Rather a sediment textural
patch mosaic was identified. Nutrient concentrations associated with the surface sediments of
the inset-floodplains were also shown to vary significantly resulting in a nutrient patch
mosaic. This spatial nutrient mosaic was enhanced by factors including the surface elevation
of the floodplain surface.
Sediment and nutrient exchange between the river channel and inset-floodplain surfaces was
measured during several flows in 2001, 2002 and 2005. Pin and sediment trap data showed
that significant quantities of sediment were exchanged between the river channel and
floodplain surfaces during inundation with both cut and fill processes occurring. Patterns in
sediment exchange appear to be related to local sediment supply and seasonal sediment
exhaustion, rather than the top down geomorphic constraints considered. These material
exchanges resulted in a change to the spatial configuration of the sediment textural patch
mosaic. Distinct new sediment textural patches were created following inundation, while
other patches were lost post inundation and other patches changed sediment textural character
to move into pre-existing patches. Thus a truly dynamic sediment textural mosaic exists
within this floodplain landscape.
Nutrient concentrations associated with floodplain sediments also changed over time. While
nutrient concentrations increased after the December 2001 flow event, they generally
decreased after the March 2002 event, highlighting their dynamic nature over time. The
spatial distribution of nutrient concentrations also varied over time, with a 40 percent change
to the nutrient mosaic as a result of the March 2002 flow event. In addition to the influence of
the changing physical template (sediment texture mosaic), nutrient concentrations were
shown to be influenced by rainfall processes on non flooded surfaces, and also a number of
top-down constraints and bottom-up influences operating over multiple spatial scales.
Overall, the inset-floodplains studied in this thesis acted primarily as sediment and nutrient
sinks, and were a source for dissolved nutrients. Nutrient exchange was associated with the
exchange of sediments in this riverine landscape, over both inter-flow and decadal timescales.
It was demonstrated that water resource development within the catchment reduced the
number, magnitude and duration of flow events down the Barwon-Darling River and as a
result reductions in the exchange of sediment, associated and dissolved nutrients between
inset-floodplains and the main river channel were calculated. The greatest reductions were
with the release of dissolved nutrients (42-25 percent) and the exchange of sediment and
associated nutrients from high level surfaces (43 percent).
Effective conservation and management of riverine ecosystems must occur at the correct
scale. This study identified potential nutrient hotspots at several scales in the Barwon-Darling
floodplain landscape that could be targeted by management. The low predictability of the
location of nutrient hotspots at the inset-floodplain scale over time means that environmental
flows should be targeted at high level surfaces (<25 000 MLD-1) that provide long term
sources of carbon to the river channel. Conserving flows of this magnitude will also reinstate
flow variability, an important facet of the Barwon-Darling River?s hydrology that has been
changed by water resource development. The research presented in this thesis highlights the
importance of not only considering pattern and process at multiple scales, but also the way in
which these processes influence landscape patterns over time, leading to the identification of
the appropriate scales that can best be targeted for the conservation of these systems.
22
Haley, Stephen Mark. "The application of sediment source fingerprinting techniques to river floodplain cores, to examine recent changes in sediment sources in selected UK river basins." Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/3137.
Анотація:
In recent years there has been an increasing awareness of the detrimental influence of diffuse sources of pollution on aquatic systems and of the integral role played by sediment in the mobilisation and transport of pollutants. The recognition of the environmental, societal and economic importance of the ecological health of aquatic environments has led to a change in emphasis regarding agricultural and environmental policy. To implement successful delivery of emerging policy requirements, there is a current need to have an enhanced understanding of the relationship between different forms of land use and sources of diffuse pollution, particularly sources of fine sediment. To understand the potential impacts of future land use changes, including environmental conservation measures on sources of sediment, it is useful to consider them within a longer-term context. This study has successfully applied the sediment source fingerprinting technique to floodplain overbank sediment cores in a retrospective study of six diverse UK river catchments with identified sediment problems. The varying estimates of relative sediment contributions from differing sources have been compared to known land use change in the study catchments over concurrent time periods, to explore any associations which might be apparent. Over the last 40 years, the increased cultivation of high erosion risk crops, such as those which are harvested late in the season (e.g. maize) and those which are sown in the autumn (e.g. winter wheat), has contributed disproportionately to the total sediment load relative to the area of land occupied by such cultivation. Increased stocking densities have resulted in increased relative sediment contributions from grassland sources, particularly intensively managed temporary grassland, but can have an even greater impact on sediment contributions derived from channel bank sources. The installation and maintenance of drainage for agriculture or for flood risk management has resulted in increased relative sediment loads from channel bank and associated sub-surface sources. Through the further development of such research, the efficacy of mitigation measures can be tested against evidence-based historic trends and those management approaches which provide identifiable improvements can be developed as best practice options for future land management targeted at reducing the negative impacts of excessive sediment ingress to river systems. The design of the source fingerprinting methodology used in this work was based on an established successful approach and this was developed further through the incorporation of a number of refinements designed to improve the robustness of the technique and expedite its implementation.
23
Ayyoubzadeh, Seyed Ali. "Hydraulic aspects of straight-compound channel flow and bed load sediment transport." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391507.
24
González, Sanchis María del Carmen. "Flooding dynamics and nutrient retention in the middle Ebro floodplain: experimental assessment and numerical modeling." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/15242.
Анотація:
El presente trabajo destaca la simulación numérica como herramienta capaz de reproducir y predecir los principales procesos que producen y mantienen los ecosistemas de llanuras de inundación. Para ello, la dinámica del flujo, la actividad geomorfológica, la sedimentación y la captura de nutrientes de la llanura de inundación, son evaluadas experimentalmente. Seguidamente, los datos experimentales son incluidos en un modelo numérico para desarrollar una herramienta completa de simulación capaz de predecir la dinámica del flujo, la actividad geomorfológica, la sedimentación, el aporte de nutrientes del río a la llanura de inundación así como la captación de los mismos. El estudio se desarrolla en un segmento del río Ebro (NE España), representativo de su tramo medio meandriforme.
El estudio emplea un modelo numérico bidimensional (2D), basado en las ecuaciones 2D de las aguas poco profundas y calculado a partir del método de los volúmenes finitos. La calibración del modelo se basa en medidas experimentales realizadas en la llanura de inundación bajo dos caudales estacionarios. La validación del modelo se llevó a cabo comparando los resultados numéricos con las medidas experimentales de nivel de agua y extensión del área inundada realizadas durante los cinco eventos de riada ocurridos en el año 2007 (79+13 % área; 0.27+0.05m nivel de agua).
Las simulaciones fueron utilizadas para analizar la dinámica actual de inundación de la llanura así como su actividad geomorfológica. Como resultado, se obtuvo que el presente régimen de caudales y sobretodo la estructura morfológica de la llanura, no resulta suficiente para generar una actividad geomorfológica tal que mantenga el mosaico cambiante de hábitats característico de los ecosistemas de llanura de inundación.
La nueva formulación que describe la retención de nutrientes se ha desarrollado mediante la utilización de los datos experimentales, en condiciones de flujo controladas, semi-controladas y en el propio río Ebro.González Sanchis, MDC. (2012). Flooding dynamics and nutrient retention in the middle Ebro floodplain: experimental assessment and numerical modeling [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/15242
Palancia
25
Eddy, Jeremy E. "EFFECTS OF HYDROLOGIC CONNECTIVITY AND LAND USE ON FLOODPLAIN SEDIMENT ACCUMULATION AT THE SAVANNAH RIVER SITE, SOUTH CAROLINA." UKnowledge, 2017. https://uknowledge.uky.edu/ees_etds/55.
Анотація:
Floodplains, and the sediment accumulating naturally on them, are important to maintain stream water quality and serve as sinks for organic and inorganic carbon. Newer theories contend that land use and hydrologic connectivity (water-mediated transport of matter, energy, and/or organisms within or between elements of the hydrologic cycle) play important roles in determining sediment accumulation on floodplains. This study hypothesizes that changes in hydrologic connectivity have a greater impact on floodplain sediment accumulation than changes in land use. Nine sediment cores from seven sub-basins were collected from the Savannah River Site (SRS), South Carolina, and processed for grain-size, radionuclide dating (7Be, 137Cs, 210Pb), particulate organic carbon (POC), and microscopy. Historical records, including aerial and satellite imagery, were used to identify anthropogenic disturbances in the sub-basins, as well as to calculate the percentages of natural vegetation land cover at the SRS in 1951, and 2014. LiDAR and field survey data identified 251 flow impediments, measured elevation, and recorded standard stream characteristics (e.g., bank height) that can affect hydrologic connectivity. Radionuclide dating was used to calculate sediment mass accumulation rates (MARs) and linear accumulation rates (LARs) for each core. Results indicate that sedimentation rates have increased across all SRS sub-basins over the past 40-50 years, shortly after site restoration and recovery efforts began. Findings show that hydrologic connectivity proxies (i.e., stream characteristics and impediments) have stronger relationships to MARs and LARs than the land use proxy (i.e., vegetation cover), confirming the hypothesis. As stream channel depth and the number of impediments increase, floodplain sedimentation rates also increase. This knowledge can help future stream restoration efforts by focusing resources to more efficiently attain stated goals, particularly in terms of floodplain sediment retention.
26
Aalto, Rolf Erhart. "Geomorphic form and process of sediment flux within an active orogen : denudation of the Bolivian Andes and sediment conveyance across the Beni Foreland /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/6718.
27
Simm, David John. "The deposition and storage of suspended sediment in contemporary floodplain systems : a case study of the River Culm, Devon." Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334992.
Анотація:
This thesis documents the rates and patterns of contemporary and recent overbank deposition along the lower reaches of the River Calm, S. E. Devon, England. Two temporal perspectives are adopted: (i) short-term rates based on contemporary flood events, using sediment traps, the sampling of in-channel suspended sediment and qualitative field observation of inundation processes; and, (ii) recent (over the past 35 years) rates of vertical accumulation, using the caesium-137 technique. These techniques also enable lateral and downstream trends to be identified. Longer-term implications are also addressed using a simple lithofacies classification of alluvial sections, supplemented by historical evidence of channel change and anthropogenic impact along the study reach. Overbank deposition rates are generally low along the study reach, averaging 0.7 mm year-1 (using estimates of suspended sediment conveyance losses), 0.4 mm year-1 (sediment traps) and 0.5 mm year-1 (caesium-137 studies). In general, the highest deposition rates are associated with the levee, depressions and breaches. Deposition rates, however, are temporally and spatially highly variable, being dependent upon the microtopographic relief and vegetation of the floodplain, the mode of inundation, and the extent of retention pondage. Anthropogenic impact on the floodplain is also noted, in particular the role of ditches in distributing floodwaters across the floodplain and the compartmentalisation effect of barriers to flow. These have important implications for the rates of overbank deposition and the sedimentological characteristics of deposits. The role of scour remobilisation of sediment is also assessed. The spatial detail afforded by the caesium-137 technique has been used to identify areas of the floodplain which may be locally susceptible to scour. This study highlights the potential for lowland floodplains undergoing regular flooding to suffer contamination from radionuclides and other pollutants, and leads to an improved understanding of the spatial and temporal rates and trends in deposition and sedimentological characteristics of overbank deposits on the floodplain of a suspension load-dominant river system.
28
Pazol, Jordan Samuel. "Effects of Floodplain Reconnection on Storm Response of Restored River Ecosystems." Ohio University Honors Tutorial College / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1618926160551753.
29
Apagu, Buba Ankidawa. "Sustainability of water abstraction by hand drilling in the floodplain of River Benue of Yola, NE Nigeria." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/8401.
Анотація:
The aim of the research is to assess the sustainability of groundwater supply and the suitability of hand-drilling techniques for accessing groundwater for irrigation practices along the shallow alluvial floodplains of River Benue, NE Nigeria. Hand-drilling techniques are affordable means for the farmers to abstract water from these shallow aquifers. Determining the most sustainable hand-drilling techniques (taking into account the hydrology and sedimentology of the floodplain) will improve farming activities and food security in this region and the country at large. Hydrological data (obtained from fieldwork and modelling) demonstrate that the River Benue is the main source for recharge of the shallow alluvial aquifers of the floodplain during the dry season period. Water table heights were estimated by resistivity survey using ABEM Terrameter equipment and measured by automatic piezometer instruments. Floodplain sedimentology and hydrogeology were assessed at seventeen natural riverbank outcrops and twelve hand-drilled boreholes. At each location, sediment samples were collected from every exposed sedimentological unit. Locations and elevations were measured using a ProMark3 dual frequency GPS instrument, to create a detailed topographic map with updated contours. Twenty-four electrical resistivity sounding profiles and twelve-groundwater measurement were also obtained to explore the groundwater level of the floodplain. The resistivity results confirm the availability of water in the alluvial aquifers of the floodplain. In order to determine the most appropriate hand drilling techniques, a Field Shear Vane Tester was used to measure sediment shear strength at twelve different borehole locations. Shear strength forces were higher on clayey silt and sandy silt, and lower on sand formations. It appeared that in some areas of the floodplain, the farmers are already above the shear strengths that can be provided by human power. Hence, any increase of the hardness of the surface of the sediment would make low-cost hand drilling impractical. Particle size analysis for the sediment samples showed that the samples were largely sandy in nature, which enables easy movement of water through the layers for aquifer recharge. Magnetic susceptibility (used to classify the source of sediment and the process of their formation) revealed that the main source of the sedimentary materials was upstream of the study site and varies little over time. The groundwater level of the study area decreased away from River Benue valley during the dry season period. One perched aquifer formations and possibly two others were observed in three different locations, which reflects a low-permeability stratigraphic unit (such as lens of clayey silt) within alluvial sands. These should be avoided by farmers, as they are likely to provide water only in the short-term. Finally, groundwater modelling was undertaken (with various scenarios) for the River Benue floodplain using acquired sedimentology and hydrology data integrated into MODFLOW software. The results revealed that low-cost hand-drilling techniques such as augering and jetting remain possible for abstracting the shallow alluvial aquifers on the floodplain for irrigation farming in the study area, unless the most likely low river water stages in River Benue, over-exploitation of the shallow alluvial floodplain groundwater and drought scenarios occur.
30
Nguyen, Van Manh [Verfasser], and Bruno [Akademischer Betreuer] Merz. "Large-scale floodplain sediment dynamics in the Mekong Delta : present state and future prospects / Van Manh Nguyen ; Betreuer: Bruno Merz." Potsdam : Universität Potsdam, 2014. http://d-nb.info/1218491116/34.
31
Song, Song [Verfasser]. "Assessment of flow and sediment transport in rivers and on floodplains ecosystem based on hydraulic modeling / Song Song." Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/1050388690/34.
32
Stout, Justin Collin. "Identifying and quantifying sediment sources and sinks in the Root River, Southeastern Minnesota." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1304.
Анотація:
Currently, our ability to predict the flux of fine sediment at the watershed scale is limited by the precision of erosion rate estimates for the many potential sources distributed throughout a landscape as well as our understanding of the connectivity of sediment pathways during transport. In absence of a robust predictive model which can be validated by measurements of sediment fluxes and use of geochemical tracers. Predicting fine sediment yield at the watershed scale requires multiple redundant lines of information. This thesis outlines the methods used, and the data sets collected in the Root River watershed in Southeastern Minnesota, all of which are multiple lines of evidence to the sediment dynamics in the Root River. The research indicates that the Root River is a very dynamic watershed. The hydrologic regime of the watershed has shifted over the last half century. Due to this shift sediment fluxes are very dependent of the magnitude and sequence of events. Geomorphic analysis of the landforms and the use of a developed tool, TerEx, indicate that many reaches of the river have easily accessible near-channel sources of sediment. Sediment fingerprinting results illustrate that source tracer concentrations are variable across the landscape, that as a whole, upland sources are still a major contributor to the suspended sediment load, and that in some sub-watersheds near-channel sources are dominate in the suspended load. Over all the channel-floodplain exchange exerts strong control on the flux of sediment through this river system.
33
Gurrola, Annika J. "Analyzing Floodplain Reconnection as a Restoration Method: Water Storage, SedimentDynamics, and Nutrient Cycling in Restored and Unrestored Streams." Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1620132487227832.
34
Ismail, Zulhilmi. "A study of overbank flows in non-vegetated and vegetated floodplains in compound meandering channels." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/7905.
Анотація:
Laboratory experiments concerning stage-discharge, flow resistance, bedforms, sediment transport and flow structures have been carried out in a meandering channel with simulated non-vegetated and vegetated floodplains for overbank flow. The effect of placing solid blocks in different arrangements as a model of rigid, unsubmerged floodplain vegetation on a floodplain adjacent to a meandering channel is considered. The aim was to investigate how density and arrangements of floodplain vegetation influence stage-discharge, flow resistance, sediment transport and flow behaviours. Stage-discharge curves, Manning's n and drag force FD are determined over 165 test runs. The results from the laboratory model tests show that the placing of solid blocks along some part of the bend sections has a significant effect on stage-discharge characteristics. The change in stage-discharge by the blocks is compared using different arrangements, including the non-vegetated floodplains case. The experimental results show that the presence of energy losses due to momentum exchange between the main channel and the floodplain as well as the different densities of the blocks on a floodplain induce additional flow resistance to the main channel flow, particularly for shallow overbank flows. In general, the results show that the density and arrangement of blocks on the floodplains are very important for stage-discharge determination and, in some cases, for sediment transport rates, especially for a mobile main channel. Also, the correction parameter, a is introduced in order to understand the effects of blocks and bedforms on the force balance equation. By applied the correction factor c; a stagedischarge rating curve can be estimated when the avalue is calibrated well. Telemac 2D and 3D were applied to predict mean velocity, secondary flow and turbulent kinetic energy. Telemac computations for non-vegetated and vegetated floodplain cases in a meandering channel generally give reasonably good predictions when compared with the measured data for both velocity and boundary shear stress in the main channel. Detailed analyses of the. predicted flow variables were therefore carried out in order to understand mean flow mechanisms and secondary flow structures in compound meandering channels. The non-vegetated and two different cases of vegetated floodplain for different relative depths were considered. For the arrangement on a non-vegetated floodplain shows how the shearing of the main channel flow as the floodplain flow plunges into and over the main channel influences the mean and turbulent flow structures, particularly in the cross-over region. While applying vegetated floodplain along a cross-over section confirmed that the minimum/reduction shearing of the main channel flow by the floodplain flow plunging into and over the main channel is observed from the cross-sectional distributions of the streamwise velocity (U), lateral velocity (V), and secondary flow vectors. In addition to that, the vegetated floödplain along the apex bend region shows a small velocity gradient within the bend apex region. However, strong secondary flow in the cross-over section suggested that the flow interaction was quite similar to the non vegetation case in the cross-over section region.
35
Barbosa, Laís Rodrigues. "Degradação anaeróbica à CH4 e CO2 e caracterização da matéria orgânica em sedimentos de reservatórios de hidrelétricas e várzeas amazônicas." Niterói, 2016. https://app.uff.br/riuff/handle/1/1540.
Анотація:
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ
Todos os corpos d’água continentais, naturais ou antrópicos, emitem gases do efeito estufa a partir da degradação da matéria orgânica (MO). Em ambientes tropicais este processo é favorecido por altas temperaturas, influenciando no ciclo global do carbono. Os objetivos deste trabalho foram: (1) avaliar as produções de CH4 e CO2 em incubações de sedimentos de reservatórios de hidrelétricas e, comparativamente, em várzeas amazônicas; e (2) caracterizar a MO que foi degradada pela atividade microbiana. Sedimentos dos reservatórios Funil, Tucuruí e Segredo; e das várzeas Curuai, Janauaca e Yahuarcaca, foram incubados em anaerobiose e analisados quanto às suas composições elementares, isotópicas e moleculares (lignina e esteróis) da MO. As várzeas produziram mais gases que os reservatórios sendo a produção de CO2 superior à de CH4 em todos os pontos. A produção de CH4 foi insignificante nos pontos de rio do reservatório Tucuruí, em Segredo e Janauaca. A várzea de Yahuarcaca apresentou as maiores taxas, com produção total de gases de 18426,13 nmol g-1d-1, num período de incubação de cerca de 3 meses, e baixos teores de lignina e carbono orgânico (CO). Curuai apresentou uma produção de 11232,35 nmol g-1d-1, e alto teor de CO (20%), NT (0,7%) e esteróis (≈ 48μ∙g-1) sendo a segunda maior produção de gases com predominância de CO2. Janauaca apresentou resultados similares, porém proporcionalmente inferiores à Curuai. Funil e o ponto central de Tucuruí produziram cerca de 4000 nmol g-1d-1, porém concentrações distintas de compostos orgânicos, maior teor de esteróis no Funil e maior teor de lignina no Tucuruí. Segredo e os pontos de rio do Tucuruí apresentaram as menores produções de gases e composições similares de lignina (≈2-4 mg∙100mgCO-1) e esteróis (≈ 5-7μ∙g-1). A composição isotópica (δ13C e δ15N) pôde ser relacionada, nas várzeas, com a predominância de plantas vasculares e constante renovação de MO e, nos reservatórios, com características de sistemas fechados e MO regenerada. As taxas de produção de CH4 e CO2 foram associadas à quantidade de MO em alguns pontos e à labilidade, determinante para sua degradação microbiana, em outros. Os fatores que possivelmente controlaram a degradação de MO foram: o teor de CO, as fontes de C e os tipos de substratos que definiram a formação de comunidades bacterianas.
All the continental water bodies, natural or man-made, emit greenhouse gases from the degradation of organic matter (OM). In tropical environments this process is facilitaded by high temperatures, influencing on the global carbon cycle. The aims of this study were to: (1) evaluate the production of CH4 and CO2 in incubations of sediments from hydroelectric reservoirs and comparatively in Amazonian floodplains; (2) characterize the OM which was degraded by microbial activity. Sediments of Funil, Tucuruí e Segredo reservoirs and Curuai, Janauaca and Yahuarcaca floodplains were incubated anaerobically and analyzed for elemental, isotopic and molecular compositions (lignin and sterols) of OM. The wetlands produced more gas than reservoirs, being the production of CO2 higher than CH4 at all points. The CH4 production was negligible at the Tucuruí reservoir river points, Segredo e Janauaca. The floodplain Yahuarcaca exhibited the highest rates with 18426,13 nmol g-1d-1 of the total production of gases in about a 3 months period and low lignin and organic carbon (OC). Curuai presented a production of 11232,35 nmol g-1d-1 and high content of OC (20%), TN (0,7%) and sterols (≈ 48μ∙g-1) being the second largest production of gases with predominance in CO2. Janauaca showed similar results, proportionately less than Curuai though. Funil and the central point of Tucuruí produced about 4000 nmol g-1d-1 however with different concentrations of organic compounds, higher content of sterols in Funil e higher lignin content in Tucuruí. Segredo and the points at Tucuruí river showed lower production of gases and similar compositions of lignin (≈ 2-4 mg∙100mgOC-1) and sterols (≈ 5-7μ∙g-1). The isotopic composition could be related the predominance of vascular plants and constant renewal of OM in the floodplains and in reservoirs with characteristics of closed systems and regenerated OM. CH4 and CO2 production rates were associated with the amount of OM in some points and with lability, determinant to microbial degradation, in others. Factors that possibly controlled the OM degradation were: the OC content, the C sources and the types of substrates that have defined the formation of bacterial communities.
36
Hughes, Andrew Owen Physical Environmental & Mathematical Sciences Australian Defence Force Academy UNSW. "An assessment of recent changes in catchment sediment sources and sinks, central Queensland, Australia." Awarded by:University of New South Wales - Australian Defence Force Academy. Physical, Environmental & Mathematical Sciences, 2009. http://handle.unsw.edu.au/1959.4/43622.
Анотація:
Spatial and temporal information on catchment sediment sources and sinks can provide an improved understanding of catchment response to human-induced disturbances. This is essential for the implementation of well-targeted catchment-management decisions. This thesis investigates the nature and timing of catchment response to human activities by examining changes in sediment sources and sinks in a dry-tropical subcatchment of the Great Barrier Reef (GBR) catchment area, in northeastern Australia. Changes in catchment sediment sources, both in terms of spatial provenance and erosion type, are determined using sediment tracing techniques. Results indicate that changes in sediment source contributions over the last 250 years can be linked directly to changes in catchment land use. Sheetwash and rill erosion from cultivated land (40-60%) and channel erosion from grazed areas (30-80%) currently contribute most sediment to the river system. Channel erosion, on a basin-wide scale, appears to be more important than previously considered in this region of Australia. Optically stimulated luminescence and 137Cs dating are used to determine pre-and post- European settlement (ca. 1850) alluvial sedimentation rates. The limitations of using 137Cs as a floodplain sediment dating tool in a low fallout environment, dominated by sediment derived from channel and cultivation sources, are identified. Low magnitude increases in post-disturbance floodplain sedimentation rates (3 to 4 times) are attributed to the naturally high sediment loads in the dry-tropics. These low increases suggest that previous predictions which reflect order of magnitude increases in post-disturbance sediment yields are likely to be overestimates. In-channel bench deposits, formed since European settlement, are common features that appear to be important stores of recently eroded material. The spatially distributed erosion/sediment yield model SedNet is applied, both with generic input parameters and locally-derived data. Outputs are evaluated against available empirically-derived data. The results suggest that previous model estimates using generic input parameters overestimate post-disturbance and underestimate predisturbance sediment yields, exaggerating the impact of European catchment disturbance. This is likely to have important implications for both local-scale and catchment-wide management scenarios in the GBR region. Suggestions for future study and the collection of important empirical data to enable more accurate model performance are made.
37
Aniceto, Keila Cristina Pereira. "Reconstrução paleohidrológica em sistemas de várzea na Amazônia Peruana." Niterói, 2016. https://app.uff.br/riuff/handle/1/1656.
Анотація:
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ
As variações paleohidrológicas pelas quais passaram os lagos Hubos e Quistococha ao longo do Holoceno Médio e Superior, foram reconstruídas através de análises semi-quantitativas e qualitativas dos argilo-minerais e dos elementos Al, Si, S, K, Ca, Mn Ti, Fe, Rb, Sr e Zr. A fim de avaliar como o Rio Amazonas influencia os processos sedimentares destes ecossistemas, determinou-se a concentração elementar de carbono (carbono orgânico total-COT) e nitrogênio (nitrogênio total-NT), composição isotópica do carbono e nitrogênio (δ13C e δ15N). O Lago Hubos, está situado próximo à confluência dos rios Ucayali e Marañon, faz parte da planície de inundação do Rio Ucayali e sua conexão com o canal principal se dá de forma indireta e através do pequeno rio Yarapá e sua distância do canal rio é de aproximadamente 2 km. A sedimentação do lago Hubos nos últimos 4130 anos cal AP, se deu sob a influência da forte dinâmica do Ucayali, que resultou em datações 14C invertidas ou com idades muito próximas em trechos extensos do testemunho. Entre 4130 e 2870 anos cal AP a concentração de COT era baixa (<1%), os valores de δ13C e δ15N do lago apresentaram uma matéria orgânica que é mistura de fitoplancton e com matéria orgânica típica de solos e plantas C3 e a presença de laminações, o que sugere um sistema de baixa energia hidrodinâmica. A assembléia mineral com assinatura típica do Ucayali, apresentou elevados percentuais de esmectita (~61%), caulinita (~15%), clorita (~8%) e ilita (18%) e a mineralogia por FRX sugere variabilidade da maior parte dos dados, sugerindo pulsos de inundação neste período. Uma lacuna na sedimentação foi observada entre 2870 e 700 anos cal AP (unidade III). Este sedimento foi caracterizado por concentrações mais elevadas de COT (4,3%), matéria orgânica originada de plantas C3, elevados percentuais de esmectita (67%), caulinita (~12%), clorita (~6%) e ilita (15%) e predominância de material intemperizado e grosso no sedimento. Após esse período, o material sedimentado era pós-moderno e bioturbado, as concentrações de COT de 2,1% e esmectita (~52%), caulinita (~29%), clorita (~4%) e ilita (15%), esta matéria orgânica é característica de solos e plantas C3, com redução de frações mais grossas no sedimento e aumento de material inalterado. O material mais superficial é antigo, provavelmente retrabalhado, com concentração de COT 1,29% e esmectita (~46%) caulinita (~12%), clorita (~26%) e ilita (18%). A FRX, sugere material de granulometria mais grossa e mais alterado quimicamente. O lago Quistococha faz parte da Reserva Quistococha, e está localizado à 10 km do centro da cidade de Iquitos e aproximadamente 10 Km do rio Amazonas. Entre cerca de 6.100 e 4.900 anos cal AP, o lago estava sob forte influência do rio Amazonas. O que induziu a maiores taxas de sedimentação (~0,5 cm ano-1), a deposição predominante foi de partículas relativamente grossas (silte grosso) e laminadas, em detrimento do material orgânico (~5%). A mineralogia da fração argila determinou percentuais de esmectita (~41%), clorita (~9%), ilita (~20%), e caulinita (~29%). A razão FRX, sugere presença de material alterado quimicamente e laminações de 0,7 cm de espessura. A diminuição da granulometria e da espessura das laminações a partir de 5800 anos cal AP, até seu completo desaparecimento indicam a perda gradual da influência do Amazonas. Um hiato foi observado a partir de 4.900 anos calAP, cujo motivo provável ainda precisa ser investigado. Condições mais seca do Holoceno Médio impediram a volta da sedimentação, que só aconteceu apos 2600 anos cal AP, com o retorno das condições mais úmidas estabelecidas durante o Holoceno Tardio. A perda da influência do rio Amazonas induziu alterações significativas na sedimentação lacustre, determinando sua atual condição de isolamento. Caracterizado por taxas de sedimentação extremamente baixas (0,02 cm ano-1), sedimentos mais finos, ricos em material orgânico (20-80%) e fração argila composta de esmectita (~35%); clorita (~5%); ilita (~16%); e caulinita (~44%)
The palaeo-hydrological variations through which passed Hubos and Quistococha lakes along the Middle and Upper Holocene were reconstructed using a semi-quantitative and qualitative analyzes of clay minerals and the elementsAl, Si, S, K, Ca, Mn Ti, Fe, Rb, Sr e Zr. In order to assess how the Amazon River influences the sedimentary processes of these ecosystems, was determined the elementary concentration of carbon (total organic carbon-TOC) and nitrogen (total nitrogen-NT), isotopic composition of carbon and nitrogen (δ13C and δ15N). The Hubos Lake, is situated near the Ucayali and Marañon rivers confluence, part of the floodplain of the Ucayali river and its connection with the main channel occurs indirectly and through small river Yarapá and its distance from the river channel is aproximately2 Km. The sedimentation of the lake Hubos in the last 4130 years cal BP, occurred under the influence of the strong dynamics of the Ucayali, which resulted in 14C datings reversed or very close in age in extensive excerpts of testimony . Between 4130 and 2870 years cal AP TOC concentration was low (<1%), the values of δ13C and δ15N of lake showed an organic matter which is mixed with phytoplankton and typical organic matter from soils and plants C3 and the presence of laminations, which suggests a system of low hydrodynamic energy. The mineral meeting with the typical signature of Ucayali showed high percentages of smectite (~ 61%), kaolinite (~ 15%), chlorite (~ 8%) and illite (18%) and mineralogy by XRF suggests variability of most data, suggesting flood pulses during this period. A gap in sedimentation was observed between 2870 and 700 cal years BP (Unit III). This sediment was characterized by higher concentrations of TOC (4.3%), organic matter originating from plants C3 smectite high percentage (67%), kaolinite (~ 12%), chlorite (~ 6%) and illite (15 %) and predominance of the weathered and coarse sediment. After this period, the settled material was postmodern and bioturbed, TOC concentrations of 2.1% and smectite (~ 52%), kaolinite (~ 29%), chlorite (~ 4%) and illite (15%) this organic matter is characteristic of soils and C3 plants, with reducing coarser fractions in the sediment and unaltered material increase. The most superficial material is old, probably reworked, with 1.29% TOC concentration and smectite (~ 46%) kaolinite (~ 12%), chlorite (~ 26%) and illite (18%). The XRF suggests a thicker granulometry and chemically altered material. The Quistococha lake is part of Quistococha Reserve, and is located 10 km from the center of Iquitos city and approximately 10 km of the Amazon River. Between about 6100 and 4900 years cal BP, the lake was under strong influence of the Amazon River. What led to higher sedimentation rates (~ 0.5 cm-1 year), was the predominant deposition of relatively coarse particles (coarse silt) and laminated, to the detriment of the organic material (~ 5%). The the clay fraction mineralogy determined percentage of smectite (~ 41%), chlorite (~ 9%), illite (~ 20%), and kaolinite (~ 29%). The XRF reason, suggests the presence of chemically altered material and laminations of 0.7 cm thick. The decrease of granulometry and the laminations thickness from 5800 cal years BP, until its complete disappearance indicate the gradual loss of the Amazon influence. A gap was observed from 4900 cal years BP, whose probable reason still needs to be investigated. Drier conditions in the Middle Holocene prevented the sedimentation return, which only happened after 2600 cal years BP, with the return of most humid conditions established during the late Holocene. The loss of influence of the Amazon river induce significant changes in lacustrine sedimentation, determining its current condition of isolation. Characterized by extremely low sedimentation rates (0.02 cm year-1), fine sediments, rich in organic material (20-80%) and clay fraction composed of smectite (~ 35%); chlorite (~ 5%); illite (~ 16%); and kaolinite (~ 44%)
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Webb, Laura D. "Historical changes in the geomorphology of the Ottawa River (NW Ohio, U.S.A.) due to urbanization and land clearance." Bowling Green State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1276534992.
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Anderson, Christopher John. "The influence of hydrology and time on productivity and soil development of created and restored wetlands." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1132540084.
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Colarossi, Debra. "Geology and geochronology of the Nyl River floodplain sediments, Limpopo province, South Africa." Thesis, 2013. http://hdl.handle.net/10539/12951.
Анотація:
A Dissertation submitted to the Faculty of Science, University of the Witwatersrand,
Johannesburg, in fulfilment of the requirements for the Degree of Master of Science
in Geology.
Johannesburg 2013The Nyl River floodplain, located in the Limpopo Province, is one of the few active sedimentary basins that exist within the South African interior, providing a unique opportunity to study the effect of climate change on fluvial systems. Progradation of tributary fans into the Nyl/Mogalakwena River has raised the surface by 30 m and forced the course of the river westwards towards the Waterberg. Periods of progradation deposited thick sequences of coarse-grained sediments with sand- to gravel-sized mean grain sizes and coarsely-skewed populations in the distal reaches of the tributary fans. These periods were interspersed with periods of relative non-deposition, when active sedimentation on the fan ceased and shallow lakes (or vleis) developed in the trunk river, resulting in deposition of fine-grained, organic-rich, floodplain sediment layers with silt-sized mean grain sizes and finely-skewed distributions in the extreme outer reaches of the tributary fan. The alternating progradational sequences and non-deposition events produced interlayered floodplain and fan deposits in the furthest reaches of the tributary fans along the banks of the Nyl/Mogalakwena River. Incised river cuts within the Rooisloot tributary fan were dated using OSL and 14C techniques. For OSL samples, the SAR protocol was used to measure the equivalent dose and the burial dose was determined using the CAM and MAM. Emission counting methods, including TSAC, GM-beta counting and HRGS were used to determine the dose-rate. The OSL ages ranged from 99 years to 3884 years, constraining the sampled deposits within the late Holocene. Although the 14C ages agreed with this range, carbon contamination of the samples resulted in inverted and overestimated ages. Based on stratigraphic relationships the non-deposition events have been dated at approximately 750–800 years ago, 600 years ago, 475 years BP and 100–150 years ago and two major periods of aggradation at ~ 800–1000 years ago and ~ 500–700 years ago. The rate of aggradation (0.29 cm/year) calculated implies that the entire 30 m deposit could have been deposited in 9 000 years. However, an independent study by McCarthy et al. (2011) proved that tributary sedimentation began prior to 220 ka. Therefore, in order to deposit 30 m of sediment over 220 ka, either the mid – late Quaternary sedimentation rate was lower than the recent past (Late Holocene) or the system periodically undergoes extensive erosion in order to flush the accumulated sediment from the tributary fan system.
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Elzidani, Emhmed Z. "The Sedimentology of Pecausett Pond: A Case Study for Sediment and Contaminants Sotrage in FloodPlain Tidal Ponds on the Lower Connecticut River." 2011. https://scholarworks.umass.edu/theses/605.
Анотація:
In this study I assess spatial and temporal patterns of sediment deposition in Pecausett Pond, located along the tidal extent of the Connecticut River, in order to assess the role of tides in the transport and storage of sediment and associated contaminants within floodplain tidal ponds. Findings reveal that tidal ponds have significantly higher rates of sedimentation compared to neighboring marshes due to the fact that these ponds have more accommodation space and receive uninterrupted tidal exchange with the main river. Tidal tie channels introduce a pulse of suspended sediment and contaminants from the main river into these ponds each flood tide, with sedimentation rates fast enough to allow settling before the subsequent ebb tide can transport these sediments back to the main river (i.e. tidal pumping). Some studies performed on the tidal floodplain of the Connecticut River show high deposition rates and have attributed periods of high accumulation to anomalously high river discharge events. However, this project shows that tides are more likely the major mechanism responsible for transporting and storing sediment and associated contaminants at backwater sites located along the tidal floodplain. Deposition rates in this 3-4 m deep pond exceed 2 cm/yr. These rates are far too high to maintain equilibrium morphology for much longer. However, ground penetrating radar surveys from the study site reveal truncated stratigraphy common to erosional unconformities, which suggest that mechanisms for sediment remobilization and removal may exist. Periods of episodic erosion therefore may be helping to maintain the morphology in this shallow environment, and allow for the high rates of short-term deposition. Further, a sudden increase in percent inorganic potentially associated with the opening or clearance of the tie-channel is observed at a sediment depth approximately between 1.9 to 2.2 m. A radiocarbon date obtained below this transition is consistent with a significant drop in sedimentation prior to this tie-channel development. High rates of sedimentation in Pecausett Pond are therefore likely relatively recent phenomena, transpiring over the last few centuries following early colonization.
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"THE SODDEN SWAMPS THAT SURROUND THEM: THREE ESSAYS CONCERNING THE LINKS BETWEEN RIVER CHANNELS AND THEIR OVERBANK ENVIRONMENTS." Tulane University, 2017.
Анотація:
acase@tulane.eduThough rivers are inextricably linked in our minds with an intermittently flooded overbank environment, surprisingly little is known about the sedimentary processes that operate there, or how they interact with those of the river. The knowledge gap is acute in deltas, where dense populations often necessitate tightly engineered control over flow patterns, leading to disconnected overbank environments that no longer receive input from the main channel. However, the need to understand sedimentary function in the overbank is also acute in deltas, as rising relative sea levels create an urgent need to manage water and sediment resources. This dissertation is presented as three primary chapters, each of which examines a different aspect of the hydrodynamic and sedimentary connection between a river’s channel and its overbank environment. In Chapter 2, my coauthors and I ask which factors enhance overbank sediment retention, and what retention rates might be considered typical in deltas. We compare the sediments stored in a crevasse splay to those transported by the river and conclude that retention rates approaching 100% might be achievable in settings that are not exposed to coastal processes. Chapter 4 is also concerned with spatial patterns of sedimentation on a delta. In it we use physical experiments to examine the influence that floods play in mobilizing sediments from the channel and storing them in the overbank environment. We find, counterintuitively, that an experiment whose input included floods has a lower proportion of floodplain to channel deposits preserved than an experiment with a constant input. Chapter 3 is focused on water and sediment dynamics in the channel in a region where significant flow is lost to the overbank environment. Here we present measurements from channel networks in the Mississippi River’s Birdsfoot Delta and show that flow loss along the channels is a critical control on channel function that causes channels of disparate sizes to behave similarly. We use our field results to inform a numerical model of channel bed evolution in a region with flow losses, and conclude that the modern flood control system in the Lower Mississippi River may have significantly changed the bed morphology.
1
Christopher R. Esposito
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Visser, Fleur. "Sediment budget for cane land on the Lower Herbert River floodplain, North Queensland, Australia." Phd thesis, 2003. http://hdl.handle.net/1885/148567.
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Burri, Nicole M. "Depositional slope surface of the western margin of the Nylsvlei, South Africa : active piedmont aggradation and sedimentation processes." Thesis, 2014.
Анотація:
The Nyl River and its floodplain are situated on the eastern foothills of the Waterberg mountain range in the Limpopo Province of South Africa. Tributaries flowing out of the Waterberg range display unusual downstream changes, as they approach and converge with the Nylsvlei (or Nyl floodplain). Tributary channels decrease in size downstream until, eventually, they disappear altogether forming unchannellized floodouts. On one such floodout, on the farm Driefontein, an actively aggrading piedmont has formed adjacent to the famous Wonderkrater peat mound, known for its pollen record dating back ~45,000 years. Sediments from the aggrading piedmont interlace with Wonderkrater’s peat layers, suggesting that as the piedmont aggrades so too does the peat mound. This setting presents a unique opportunity to study active aggradational processes, and their products, on hillslope deposits and floodout environments. This study aims to describe the geomorphology and nature of depositional processes along the length of the piedmont adjacent to the Wonderkrater peat mound. Cross-sections, drainage channels and vegetation indices based on topographic maps, orthophotographs and hyperspectral images, were created using ArcGIS in order to describe and determine the surface morphology and hydrology of the Driefontein piedmont in detail. Surface soil samples were collected in order to determine particle size distribution, which were in turn compared to vegetation indices and changes in slope elevation. Further grain samples were collected from depth for age dating using Optically Stimulated Luminescence (OSL), as well as to determine grain size distribution in relation to surface sediments and other fluvial environments. Hyperspectral indices were found to correlate to surface grain size distribution, demonstrating that the presence of vegetation acts as a retaining mechanism for particles along hillslopes where incline should be too steep to support fine-grained sedimentary material. Surface sediments were found to demonstrate the characteristics of an alluvial floodout system, affected greatly by the presence of vegetation and slope inclination. Sub-surface samples were characteristic of a colluvial setting, suggesting that pediment retreat and basin fill, coupled with evidential climatic changes, were dominant controls on the pediment’s morphological and aggradational mechanisms. OSL age results estimated the sediments to be between 37.33 and 58.66 ka old. As a result of its unique sedimentary characteristics, a new type of ‘slow creep fan’ class was established in order to describe the characteristics of the Driefontein piedmont.
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HEROVÁ, Zdenka. "Obnova vegetace revitalizovaného úseku řeky Stropnice." Master's thesis, 2016. http://www.nusl.cz/ntk/nusl-381071.
Анотація:
Three seasons of initial succession were followed in the frame of this thesis after a restoration project in a section of the Stropnice River and its floodplain. The succession tends towards formation of community of alluvial meadows, which is prevailing biotope in the neighborhood of the restored part. Strong factor influencing the course of succession is wetness of the substrate, which is partially given by distance of a site from the water-course and by the difference in the altitude of a site and of the river water table. Synantrophic species were most abundant in the first year (2014), followed by meadow and wetland species (2015, 2016).