Siga este enlace para ver otros tipos de publicaciones sobre el tema: River processes.
Tesis sobre el tema "River processes"
Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros
Consulte los 50 mejores tesis para su investigación sobre el tema "River processes".
Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.
También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.
Explore tesis sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.
1
Tassi, Pablo. "Numerical modelling of river processes: flow and river bed deformation". Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/57998.
Texto completo
2
Pernik, Maribeth. "Mixing processes in a river-floodplain system". Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/19514.
Texto completo
3
Dong, Na. "Border ice processes on the Saint Lawrence River". Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28450/28450.pdf.
Texto completoResumen
Border ice is one of many ice freeze-up processes, but it is discussed only to a limited extent in the literature. Border ice formation can be a precursor for ice jam formation that may restrict navigation and lead to flooding. This master’s thesis is mainly devoted to the research on the border ice on the Saint Lawrence River from Montréal to Québec City. This reach stays artificially open all winter because commercial ships are continuously preventing a full ice cover to form. The traffic also limits the extent of border ice.
This study provides key information on ice formation and decay. Through analysis of Environment Canada’s historical data (ice charts from 2004 to 2009), the areal coverage of border ice is analyzed during freeze-up, winter and breakup periods. The historical information of ice coverage is collected in order to find out the factors which influence its formation and its spatial limits. Border ice growth and decay rates are also discussed.
The thesis shows that border ice coverage has three stages including the rapid growth period at the beginning of the winter, the relatively stable period in the mid-winter and the breakup period as March progresses. During the mid-winter period, the border ice coverage sometimes drops sharply if the air temperature rises above 0 °C and/or if there is some rain. It was also found that the maximum border ice spatial limits are quite similar over the five winter seasons.
Based on the analysis of the ice charts, a number of empirical laws regarding the formation and decay of border ice are proposed. Along the river flowing direction, the border ice is formed easily when there are obstacles particularly at the downstream end. The obstacles could include river bends, ice booms, shoals, artificial islands, bridge piers and so on. Thus, the obstacle influences the flow velocity, which is an important factor for ice formation and also provides an object against which the ice can become fast and initiate its formation.
On average, border ice reaches 20% of its maximum coverage when the accumulated freezing degree days (AFDD) reaches 124 °C-D. This is followed by a rapid growth period that ends when the ice cover reaches about 80% of its maximum cover corresponding to AFDD equal to 247 °C-D. Border ice coverage usually reaches the maximum value when the average AFDD is 551 °C-D corresponding to the end of January.
The winter period is characterised by a stable ice cover (>90% of max) upstream of Trois-Rivières except in the event of a mid-winter thaw. Downstream of Trois-Rivières there is no stable period as the decay begins very soon after the ice reaches its maximum value.
Breakup is a gradual process that normally begins on about Feb. 15th downstream of Trois- Rivières and about March 1st upstream. Most ice has normally gone by March 31st.
Moreover, the river flow velocity, river depth and Froude number along the limits of border ice once it reaches its maximal areal coverage are evaluated and analyzed. The flow velocity is almost always less than 1.0 m/s; the maximum Froude number is normally 0.1 at Lake Saint-Pierre and 0.2 in the Montréal to Sorel reach; river depth at the ice edge can vary widely.
Through numerical modelling, it was found that border ice increased the current velocity by 0.1 m/s in the Lake Saint-Pierre reach and raised water levels by 14 cm in the Montréal to Sorel reach.La glace de rive est un des nombreux processus de formation des couverts de glace sur les rivières. Cependant peu d’articles dans la littérature traitent de ce sujet malgré que la formation de la glace de rive peut-être un précurseur de l’apparition d’embâcles qui peuvent entrainer des inondations. Ce mémoire de Maitrise porte sur l’étude de la glace de rive le long de la portion du fleuve Saint-Laurent allant de Montréal à Québec. Du fait qu’il y a de la navigation commerciale toute l’année, le fleuve reste ouvert (libre d’un couvert de glace entier) artificiellement pendant tout l’hiver. Ce trafic limite aussi l’extension de la glace de rive. Cette étude fournit des informations clés sur la formation et la désagrégation de la glace de rive. À partir des données historiques d’Environnement Canada (cartes des glaces de 2004 à 2009), la répartition superficielle de la glace de rive est analysée pour les périodes de formation, de stabilité et de rupture de la glace. Les informations historiques sur les couvertures de glace sont collectées afin de déterminer les paramètres qui influencent la formation et les limites spatiales de ce type de glace. Les taux de croissance et de décomposition de la glace de rive sont aussi abordés. Il est montré que l’évolution de la structure propre à la couverture de la glace de rive se fait en trois étapes. Une période de formation rapide (début hiver), suivie d’une période stable (milieu d’hiver) et enfin une période de rupture (pendant le moi de mars). Pendant la période stable, la glace de rive se rompt partiellement parfois lorsque la température de l’air monte au dessus de zéro °C et surtout lorsque le redoux est accompagné de pluie. Il a été trouvé aussi que les limites spatiales maximales des glaces de rive sont très semblables sur 5 hivers de la période d’étude. À partir de l’analyse des cartes des glaces, un certain nombre de relations empiriques sont proposées. Ces relations caractérisent la formation et la désagrégation des glaces de rive. Le long de la direction de l’écoulement la glace de rive est formée facilement en présence d’obstacles, et particulièrement lorsqu’elles sont à l’extrémité aval. Parmi ces obstacles on peut citer les méandres de rivière, les bancs, les estacades, les iles artificielles, les piliers de ponts. Ainsi, les obstacles influencent la vitesse d’écoulement qui est un paramètre important dans la formation de la glace et peut aussi effectuer un apport d’objets sur lesquels la glace peut s’attacher et initier son accroissement. En moyenne la glace de rive atteint 20% de sa couverture maximale lorsque son le nombre de degrés jours accumulés (DJA) atteint 124 °C-j. Ceci est suivi d’une période d’accroissement rapide qui prend fin lorsque la couverture de glace atteint 80% de son maximum qui correspond à un DJA de 247 °C-j. La couverture de glace de rive atteint son maximum lorsque le DJA atteint 551 °C-j; ce qui correspond normalement à la période de fin janvier. La période d’hiver est caractérisée par une couverture de glace stable (supérieure à 90% de son maximum) en amont de Trois-Rivières, sauf pendant les périodes de dégel mi hivernales. À l’aval de Trois-Rivières, il n’y a pas de période stable, vu que la désagrégation commence très tôt après que la glace ait cru à son étendu maximal. La rupture est un processus graduel qui normalement commence vers le 15 février en aval de Trois-Rivières et vers le premier mars en amont. La grande majorité de la glace disparait généralement avant le 31 mars. Par ailleurs, la vitesse d’écoulement de la rivière, ainsi que sa profondeur et son nombre de Froude le long des limites de la glace de rive sont évalués. Ceci dans la condition où la glace de rive a atteint sa répartition superficielle maximale. La vitesse est presque toujours inférieure à 1 m/s, le nombre de Froude maximal est normalement de 0,1 au dans le Lac St Pierre et de 0,2 sur le tronçon Montréal-Sorel. La profondeur de la rivière à la limite de la glace peut varier largement. À partir d’une modélisation numérique, il a été calculé que la glace de rive cause une augmentation de la vitesse de 0,1 m/s dans le chenal maritime du Lac St Pierre et du niveau d’eau de 14 cm dans le tronçon Montréal-Sorel.
4
Trieu, Hai Q. "Bank erosion processes along the lower Mekong River". Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/340011/.
Texto completoResumen
This project conducts an analysis of bank erosion processes on a large, monsoonaffected river, the Lower Mekong River in Laos. The methodological approach taken was to build integrated models of bank erosion processes at three study sites on the Lower Mekong River in Laos (Friendship Bridge, Ang Nyay and Pakse) to simulate processes of (i) groundwater seepage and pore water pressure evolution, (ii) the effect of this on mass-wasting (using the Geo-slope model) and, (iii) fluvial erosion (using a model adapted from Kean and Smith, 2006ab). In all cases the models were parameterised using measured bank geotechnical properties. Across the study sites, a total of 42 simulations were undertaken to represent a wide range of observed flow events. Specifically, 14 selected flow hydrographs (comprising three types: single peak, multiple peak and rapid fall) were evaluated at each of the study sites, such that the influence on bank erosion of the hydrological properties of different monsoon floods could be evaluated. The main findings indicate that although the Mekong is a big river, its dominant bank erosion process is one of slow, gradual, fluvial erosion. This research forms a partial contribution to understanding bank erosion processes operating in the Mekong. It was found that bank stability on the Mekong responses to variations in flood magnitude in ways that are similar to other rivers located within humid temperate areas. However, the Mekong has had the greater stability than these rivers due to its greater bank heights and more consolidated bank materials.
5
Headey, Jonathan Mark. "Modelling of river corridors : modelling urban particulate transport processes". Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289714.
Texto completo
6
Markham, Andrew James. "Flow and sediment processes in gravel-bed river bends". Thesis, Queen Mary, University of London, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308275.
Texto completo
7
Phillips, Zachary Rockford. "Holocene Postglacial Fluvial Processes and Landforms in Low Relief Landscapes". Diss., North Dakota State University, 2020. https://hdl.handle.net/10365/32036.
Texto completoResumen
Postglacial rivers are part of the relatively young low-relief landscape system left behind by glaciers. Over time, postglacial rivers are susceptible to both minor and major channel planform changes as the Earth and its newly exposed rivers adjust to new isostatic and geomorphic equilibriums. Those planform changes result in topographic features that are well preserved among the largely unaltered landscape and offer opportunities to learn about the processes that create them. This work focuses on those minor and major planform changes and the resulting landforms, with a focus on processes effecting the glaciolacustrine Red River Valley. Here, three studies were conducted, two regarding minor planform changes and one focusing on major planform changes. Studies included in this work regard 1) the spatial distribution of meander cutoffs and meander cutoff relief on the Red River, 2), avulsion timing and length resulting from isostatic tilting and 3) mobile river ice and bank interaction frequency, locations, and erosion in meandering rivers. Results show that rivers develop meander cutoffs that faster in areas where geologic materials are more easily eroded and their relief shows a positive relationship with the rate of river incision. Major channel path changes (avulsions) in the presence of isostatic tilting were found to be most frequent soon after river establishment while rates of isostatic rebound are high enough to outpace channel incision. River ice was found to most frequently interact with the outer banks of channels with long, tight bends and high sinuosity, potentially contributing to the meandering process. From these results it can be interpreted that postglacial rivers were highly dynamic early in their history and have stabilized over time, with most of the changes occurring in areas with more erodible alluvium. Presently, rivers undergo most of their changes during the spring thaw when mobile river ice is impacting the banks, with sinuous river reaches impacted most frequently by mobile river ice.North Dakota Water Recourses Research Institute (ND WRRI) Fellowship Program
8
Allread, Tyler M. "Channel Narrowing of the Green River near Green River, Utah: History, Rates, and Processes of Narrowing". DigitalCommons@USU, 1997. https://digitalcommons.usu.edu/etd/6525.
Texto completoResumen
Previous scientific research has documented channel narrowing on the Green River near Green River, Utah, but the exact timing, rates, and causal mechanisms of that narrowing have been the source of disagreement in the scientific literature. This thesis demonstrates that the Green River has narrowed in two separate periods during the last 100 years. The narrowing is driven primarily by changes in the hydrologic regime and not by the invasion of saltcedar. The channel narrowed between 1930 and 1938, when a shift from wetter than normal conditions to a period of draught led to a reduction in river discharge. Channel width then remained relatively stable until construction of Flaming Gorge Dam in 1962, despite the presence of saltcedar. Narrowing has occurred since dam construction.
Detailed analysis of the formation of an inset floodplain deposit indicates that it formed by a process of vertical accretion, during incremental events. Inset bank deposits within the study area are composed primarily of particles smaller than 0.125 mm. Measurement of suspended sand distribution within the water column shows that particles of this size are carried in suspension by the 2-yr flood. Continued vertical accretion over time elevated the floodplain surface until inundation rarely occurs.
9
Moretto, J. "Linking River Channel Forms and Processes in Gravel Bed Rivers: Time, Space, Remote Sensing and Uncertainty". Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423802.
Texto completoResumen
The “modern” fluvial morphology, is the results of a series of events characterized by both natural and human dynamics. Recognizing the process responsible for particular morphology is not a simple analysis, it can be more difficult or impossible if the data collected have too low resolution or too high uncertainty in relation to the spatial and temporal scale assessed.
This work aims to analyse and optimize different data and collection methods, derived from different time, space and resolution scales, with a good equilibrium between time-consuming and results at low uncertainty.
Different gravel bed reaches were analysed as study area: Brenta, Piave, Tagliamento River (Italy) and Feshie River (Scotland).
Three geomorphic analyses were applied at different spatial and temporal scale. A planimetric approach through a multitemporal analysis over the last 30 years on the Brenta River. A volumetric approach through a revised colour bathymetry; hybrid digital terrain models (HDTM) building and comparison of different digital elevation models (DoD) was used to study relevant flood events that occurred in the North-East Italian rivers (Brenta, Piave and Tagliamento). A highly detailed resolution, derived from Terrestrial Laser Scanner (TLS) to study its uncertainty, was applied on the Feshie River and to some laboratory experiments.
Results show that on the Brenta River, lower active channel narrowing happened from 1981 to 1990 even if relatively important floods occurred. The active channel was likely at its minimum extent due to still relevant human impacts. Partial recovery of the active channel width was detected from 1990 to 2011 due to less gravel mining and human pressure.
The proposed methodology for producing high-resolution Digital Terrain Models (DTMs) in wet areas has an uncertainty comparable to LiDAR (Light Detection And Ranging) data in dry areas. The bathymetric model calibration only requires a dGPS survey in the wet areas contemporary to aerial images acquisition. Detailed and automatic erosion - deposition analyses starting from a DoD are possible thanks to the “principal erosion deposition analyser” script developed.
Density, angle of incidence and laser intensity seem to be the most uncertain influencing factors in DTMs building from TLS point clouds. A new TLS filter developed provides semi-automatic point cloud classifications to filter the vegetation.
The geomorphic approaches presented provide an adequate topographical description of the rivers to explore channel adjustments due to natural and human causes at different spatial and temporal scales. The study represents a valuable tool for any fluvial engineering, river topography description, river management, ecology and restoration purposes.La “moderna” morfologia fluviale, è il risultato di una serie di eventi caratterizzati da differenti dinamiche, naturali ed antropiche. Riconoscere i processi responsabili di una particolare morfologia, può divenire complesso se i dati disponibili presentano bassi livelli di risoluzione o eccessiva incertezza in funzione della scala temporale e spaziale analizzata. Questo lavoro si è focalizzato ad analizzare ed ottimizzare differenti tipi di dati e metodologie di rilievo in differenti tratti fluviali a fondo ghiaioso dell’Italia Nord-Orientale e della Scozia: Fiume Brenta, Piave e Tagliamento (Italia) e Fiume Feshie (Scozia). Tre differenti metodologie geomorfometriche sono state applicate a diverse scale spaziali e temporali. Un approccio planimetrico attraverso un’analisi multitemporale degl’ultimi 30 anni in un tratto del Fiume Brenta. Un approccio volumetrico attraverso una rivisitata applicazione di batimetria da colore, con costruzione di modelli digitali del terreno “ibridi” (HDTM) e comparazione di modelli di elevazione (DoD) per lo studio di un intenso evento di piena, avvenuto nei fiumi italiani considerati. Rilievi in laboratorio e nel Fiume Feshie ad alta risoluzione, tramite laser scanner terrestre (TLS), sono stati eseguiti per studiarne l’incertezza ed individuare metodologie di classificazione spaziale delle nuvole di punti. I risultati, mostrano che dal 1981 al 1990 nel Fiume Brenta persiste ancora un processo di restringimento dell’alveo attivo. L’impatto umano è ancora presente. L’alveo attivo presenta la sua minima estensione. Dal 1990 al 2011, sembra che un parziale recupero della larghezza dell’alveo attivo sia in atto. Minor pressione da estrazione di ghiaia e da impatto umano, caratterizzano questo periodo. La metodologia proposta per produrre DTM ad alta risoluzione in presenza di aree bagnate ha dimostrato un’incertezza comparabile con il LiDAR nelle aree secche. La calibrazione dei modelli batimetrici, richiede un rilievo dGPS nelle aree bagnate in “contemporaneo” con l’acquisizione delle foto aeree. Grazie allo script sviluppato (PrEDA), sono possibili più dettagliate e automatiche analisi dell’erosione e della deposizione. Densità, angolo di incidenza ed intensità laser sembrano essere i fattori che maggiormente influenzano l’incertezza nella realizzazione di modelli di elevazione da TLS. Il filtro sviluppato per nuvole TLS è in grado di fornire semi-automatici filtraggi della vegetazione. Gli approcci geomorfometrici presentati, forniscono adeguate descrizioni topografiche dei sistemi fluviali; utili ad esplorare aggiustamenti dei canali dovuti a cause naturali o antropiche in differenti scale spaziali e temporali. Lo studio proposto, può rappresentare un valido supporto alla topografia in ambito fluviale, alla progettazione di interventi di ingegneria fluviale, ad una adeguata gestione fluviale, considerando aspetti ecologici e di riqualificazione fluviale.
10
Ansari, Saber. "Automated Monitoring of River Ice Processes from Shore-based Imagery". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35180.
Texto completoResumen
Ice plays an important role in hydraulic processes of rivers in cold regions such as Canada. The formation, progression, recession and breakup of river ice cover known as river ice processes affect river hydraulics, sediment transport characteristics as well as river morphology. Ice jamming and break up are responsible of winter flash floods, river bed modification and bank scour. River ice cover monitoring using terrestrial images from cameras installed on the shores can help monitor and understand river ice processes. In this study, the benefits of terrestrial monitoring of river ice using a camera installed on the shore are evaluated. A time-lapse camera system was installed during three consecutive winters at two locations on the shores of the Lower Nelson River, in Northern Manitoba and programmed to take an image of the river ice cover approximatively every hour. An image analysis algorithm was then developed to automatically extract quantitative characteristics of the river ice cover from the captured images. The developed algorithm consists of four main steps: preprocessing, image registration, georectification and river ice detection. The contributions of this thesis include the development of a novel approach for performing georectification while accounting for a fluctuating water surface elevation, and the use of categorization approach and a locally adaptive image thresholding technique for target detection. The developed algorithm was able to detect and quantify important river ice cover characteristics such as the area covered by ice, border ice progression and ablation rate, and river ice break up processes with an acceptable accuracy.
11
Harris, N. M. "Spatial Changes in Bank Erosion Processes in the River Severn". Thesis, University of Birmingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496467.
Texto completo
12
Bailey, Eva Machelor. "Processes Affecting Macroalgal-Seagrass Dynamics in the York River, Virginia". W&M ScholarWorks, 1998. https://scholarworks.wm.edu/etd/1539617969.
Texto completo
13
Potucek, Mark J. "Channel Change Processes and Rates in a Mixed Alluvial-Bedrock River, Huron River, North-Central Ohio (U.S.A.)". Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1498841176288786.
Texto completo
14
Bigelow, Sarah Grace y University of Lethbridge Faculty of Arts and Science. "Impacts of flow augmentation on river channel processes and riparian vegetation". Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2006, 2006. http://hdl.handle.net/10133/649.
Texto completoResumen
The Little Bow River Project was implemented in 2003 and includes Alberta’s newest dam. The Project involves tripling the diversion of water from the Highwood River to the Little Bow River and subsequently storing the water in the Twin Valley Reservoir. This MSc Thesis provided part of the environmental monitoring for that Project and particularly investigated the impacts of augmented flows on the river channel and riparian vegetation along the upper reach of the Little Bow River. An initial component of the long-term study was to determine the existing associations between fluvial geomorphic characteristics and riparian plant communities. Poplar (Populus balsamifera L.), willow (Salix bebbiana Sargent and S. exigua Nutt.) and wolf-willow (Elaeagnus commutata Bernh.) communities were located along the upper section of the river, where the channel had a steeper gradient and was narrower and more sinuous. Cattail (Typha latifolia L.) and grass (grasses and sedges) communities were generally located along the lower section of the river that was shallower in gradient, wider and straighter. Plant community distribution also reflected impacts from cattle grazing. Initial channel and vegetation responses in the first two years following the increase in flow augmentation were slight and included bank slumping, sediment scour and inundation of flooded zones. The initial responses are consistent with the primary prediction of channel widening and this will probably be associated with some changes in the adjacent riparian plant communities.xiv, 139 leaves : ill. (some col.) ; 29 cm.
15
Burge, Leif M. "Meandering river eddy accretions, sedimentology, morphology, architectural geometry, and depositional processes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq24650.pdf.
Texto completo
16
REFAAT, Hossam El-din A. A. "THE FORMATION AND REDUCTION PROCESSES OF RIVER DELTAS AND THEIR CONTROL". Kyoto University, 1990. http://hdl.handle.net/2433/131967.
Texto completo
17
Pappalardo, Giusy. "Starting from the River Again. Community Processes to Regenerate Spoiled Ecosystems". Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1630.
Texto completoResumen
Rivers and their ecosystems are a vital core of human societies: not only do they provide resources, in particular for rural economies, they also generate symbolic meanings in different cultures around the world. The Dissertation focuses on how watershed planning and management can be enhanced with the purpose of improving the relationship of human communities and natural ecosystems. This work is located within the growing debate, in the field of environmental planning, focused on the necessity to integrate scientific knowledge with a broader understanding of how social-ecological system works (Gunderson and Hollings 2001) and how communities use various types of knowledge to innovate the way they relate with natural resources; (Ostrom 2009, Fischer 2009). Two detailed cases are presented: the Mississippi communities relating with the Delta-Yazoo River basin and Pascuagoula River basin, MS, U.S.A.; the Simeto communities relating with the Simeto River Valley, Sicily, Italy. In both cases, innovating watershed planning through stakeholders collaboration faces significant difficulties, related with long-term socio-cultural struggles. Mississippi is explored through Case Study Research; the inquiry identifies the necessity of questioning bottom-up and collaborative practices in the light of reflections about dynamics of power; research also shows that even in a very challenging context there are windows of opportunities; in this case, various stakeholders agree on the necessity of improving various forms of education, integrating environmental and social-cultural issues. The Mississippi case highlights a clear indication, for planning discipline, to bridge the traditional divide between scientific environmental knowledge and the problem of democracy. The Simeto case is a narrative of the direct engagement of the author in a Participatory Action Research (PAR) process, which was generated with questions about the need of linking environmental restoration with social-cultural and democratic innovations, so that the Mississippi conclusions are the starting point of the Simeto narrative. According with the nature of PAR methodology, in which knowledge is collectively produced and continuously reshaped through action, the narrative shows how the Simeto community has learned through a democratic approach to research, in order to innovate watershed planning, to promote the democratic dialogue and to affect institutions. From a methodological standpoint, the Dissertation discusses how Case Study Research relates with Participatory Action Research. The Dissertation offers various details on practical devices, mostly related to the need of facing challenges and changes through a process of collective re-framing and through community-based education, not only to enhance the health of river s ecosystem, but also to improve communities quality of life.
Fischer, F., 2009. Democracy & Expertise. Reorienting policy inquiry. Oxford University Press.
Gunderson, L., Holling C., 2001. Panarchy: understanding transformations in human and natural systems. Island Press.
Ostrom, E., 2009. A General Framework for Analyzing Sustainability of Social-Ecological Systems, Science.
18
Jung, Kwansue 1959. "The comparative sediment processes in channel and overbank". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277205.
Texto completoResumen
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.
19
Wu, Yiping. "Investigation of integrated terrestrial processes over the East River basin in South China". Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43085799.
Texto completo
20
Tsou, Ching-Ying. "Landscape Evolution by Fluvial Processes and Gravitational Slope Processes in Tectonically Active Mountains in Taiwan". 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188494.
Texto completo
21
Holt, Tom. "The effect of proposed Soviet river diversions on Arctic Sea ice processes". Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278089.
Texto completo
22
Ashbridge, David A. J. "Processes of river bank erosion and their contribution to the suspended sediment load of the River Culm, Devon, England". Thesis, University of Exeter, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253515.
Texto completo
23
Budi, Santoso Eko. "Tidal anomalies at river entrances and the physical processes which generate them /". St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17707.pdf.
Texto completo
24
Piqué, Altés Gemma. "Analysis of hydro-sedimentary processes and impacts affecting river basins and channels". Doctoral thesis, Universitat de Lleida, 2017. http://hdl.handle.net/10803/405448.
Texto completoResumen
Aquesta tesi estudia la dinàmica hidro-sedimentària de rius mediterranis, tant ‘naturals’ com regulats per preses. Amb aquest objectiu, s’ha realizat un estudi a escala multi-temporal i multi-espacial, que inclou treball de camp en trams de riu representatius, l’anàlisi de dades a nivell de conca, i experiments en canals de laboratori. L’alteració hidrològica aigües avall dels embassaments s’ha observat a diferents escales temporals, afectant notablement la magnitud i freqüència de les crescudes. A nivell sedimentari, s’observa un dèficit de sediments, fet que facilita l’establiment de biofilm i que, a la vegada, afavoreix l’estabilització del llit del riu. A més, l’emmagatzematge temporal de sediments a la llera modula el balanç i regula l’entrada de sediments en embassaments. La tesi mostra els efectes d’un conjunt d’activitats antròpiques en procesos fluvials i com això altera les interaccions bio-físiques del riu, i posa èmfasi en la necessitat d’una gestió contínua per la preservació dels ecosistemes fluvials.Esta tesis estudia la dinámica hidro-sedimentaria de ríos mediterráneos, tanto ‘naturales’ como regulados por presas. Con este objetivo, se ha realizado un estudio a escala multi-temporal y multi-espacial, que incluye trabajo de campo en tramos de río representativos, análisis de datos a nivel de cuenca, y experimentos en canales de laboratorio. La alteración hidrológica aguas abajo de los embalses se ha observado a diferentes escalas temporales, afectando notablemente la magnitud y frecuencia de las crecidas. A nivel sedimentario, se observa un déficit de sedimentos, lo que facilita el establecimiento de biofilm y, a la vez, favorece la estabilización del lecho del río. Además, el almacenamiento temporal de sedimentos en el lecho modula el balance y regula la entrada de sedimentos en embalses. La tesis muestra los efectos de un conjunto de actividades antrópicas en procesos fluviales y en la alteración en las interacciones bio-físicas del río, y enfatiza la necesidad de una gestión continua para la preservación de los ecosistemas fluviales.
This PhD thesis studies hydro-sedimentary dynamics in Mediterranean rivers, both in ‘natural’ and in dammed rivers. For this purpose, a multi-temporal and spatial research was carried out, including field measurements in representative river reaches, data analysis at the basin scale, and experiments in artificial streams. The hydrological alteration downstream from dams was documented at different temporal scales, notably affecting the magnitude and frequency of floods. Regarding sediments, a severe deficit was observed below dams, a fact that facilitates the establishment of biofilm which, in turn, favours river bed stabilisation. Moreover, the study shows how in-channel storage influences the river sediment budget and regulates sediment input in reservoirs. The thesis examines the effects of a suit of human activities on fluvial processes and how this alter rivers’ bio-physical interactions, and emphasises the need of continuous monitoring of all these processes to achieve a sound management of fluvial ecosystems.
25
Bever, Aaron J. "Physical Processes Behind Delta Propagation and Flood Layer Dynamics, Po River, Italy". W&M ScholarWorks, 2006. http://www.vims.edu/library/Theses/Bever06.pdf.
Texto completo
26
Carver, Robert. "Inferring hydrogeologic processes with distributed temperature sensing in Indian River Bay, Delaware". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114580.
Texto completoResumen
The interaction between coastal aquifers and estuaries governs many important ecological and water quality processes. The purpose of this research is to use distributed temperature sensing (DTS) in the Indian River Bay estuary, Delaware, to detect differences in variance and mean of temperature at the sediment-water interface. DTS uses the scatter of laser light in a fibre optic cable as a means to repeatedly measure temperature to 0.1˚C at 1m intervals along the length of the cable. Low variances in temperature are interpreted as being the result of the moderating thermal influence of groundwater discharge. From September 16 to 19 2011, two kilometres of DTS cable were deployed in the near shore environment of Holts Landing State Park. Variance increases with distance from shore as the power function s2=-33.63(d ( 1.012)) + 2.685 (r2=0.78). Narrow zones with significantly lower temperature variances (Kruskal-Wallis with Tukey's HSD, p<0.05) and means (Friedman with Tukey's HSD, p<0.05) than adjoining zones exist within the near shore area. Zones of high variance at the western and eastern edges of the study site are associated with ancient shallow peat-filled valleys capped with fine sediments. A broad zone of low variance next to the western valley is interpreted to imply that over-pressured fresh groundwater is discharging at the paleo-valley margins, creating a pattern of submarine groundwater discharge which differs from existing models. An attempt to use diurnal temperature signal amplitudes at various sediment depths to calculate vertical porewater flux were unsuccessful, likely due to rapidly-rising temperatures, interference between tidal and diurnal signals, and a short measurement period. DTS appears to hold promise in detecting temperature patterns simultaneously across different scales, and can be used to rapidly fill in gaps of knowledge in hydrogeologic systems.Les interactions entre les aquifères côtiers et les estuaires régissent beaucoup de processus écologiques importants qui ont des implications sur la qualité de l'eau souterraine et marine. La compréhension de la nature et de l'ampleur de ces interactions est devenu un foyer de recherches, facilité par des avances récentes dans notre capacité de détecter la décharge submersible d'eaux souterraines. Cette étude emploie la détection distribuée de température (DDT) dans l'estuaire de la baie Indian River, sur la côte du Delaware, afin de détecter des différences dans la variance et la moyenne de la température des eaux à l'interface entre la baie et le sédiment dans la zone près du rivage du parc Holts Landing. Des variances basses sont interprétées comme étant le résultat de l'influence de modération des eaux souterraines, compatible avec les autres études, et le fait que les zones peu profondes près du rivage, qui devraient éprouver plus de variation de la température que des zones plus profondes, sont au contraire plus stables. La variance augmente avec la distance du rivage à mesure que la fonction s2=-33.63 (d(- 1.012)) +2.685 (r2=0.78). Près du rivage, il y a des endroits étroits avec des variances (Kruskal-Wallis avec Tukey's HSD, p<0.05) et moyens (Friedman avec Tukey's HSD, p<0.05) sensiblement plus basse que leurs zones proximales. Des zones de la variance élevée aux bords a l'ouest et l'est de l'emplacement d'étude sont associées aux anciennes vallées peu profondes remplies de la tourbe et maintenant couvertes avec les sédiments fins. Une large bande de bas désaccord à côté de la vallée occidentale implique que les eaux souterraines fraîches sosu pression élevée coulent aux marges de la vallée, créant un modèle du SGD qui n'équipe pas des modèles précédents. Une tentative d'employer des amplitudes de signal de la température à de diverses profondeurs de sédiment pour calculer le flux vertical d'eau interstitielle a échoué, probablement en raison des temperatures croissantes, interférence entre les signaux de la marée et diurne, et une période d'échantillon courte. DDT semble tenir la promesse en détectant des tendences de la température à travers différentes gammes simultanément, et peut être employé pour trouver les pieces manquantes de la connaissance des systèmes hydrogéologiques.
27
Mvandaba, Vuyelwa. "Understanding and quantifying channel transmission loss processes in the Limpopo River Basin". Thesis, Rhodes University, 2018. http://hdl.handle.net/10962/63797.
Texto completoResumen
Water availability is one of the major societal issues facing the world. The ability to understand and quantify the impact of key hydrological processes on the availability of water resources is therefore integral to ensuring equitable and sustainable resource management. A review of previous hydrological studies conducted in the Limpopo River Basin has revealed a gap in the understanding of surface water-groundwater interactions, particularly channel transmission loss processes. These earlier studies, focused largely on the Limpopo River’s main stem, have attributed the existence of these streamflow losses to the presence of significant alluvial aquifers and indicated that the losses account for about 30 percent (or 1000 Mm3 a-1) of the basin’s water balance. The work conducted in this dissertation reports on the delineation of alluvial aquifers across three sub-basins of the Limpopo River Basin namely, the Mokolo (South Africa), Motloutse (Botswana) and Mzingwane (Zimbabwe) sub-basins and the estimation of potential channel transmission losses based on the alluvial aquifer properties. Additionally, an assessment of the different approaches that can be applied to simulate these channel transmission losses in the Pitman Model is presented. To delineate alluvial aquifers, general land cover classes including alluvial aquifers were produced from Landsat-8 imagery through image classification. The areal extent of the delineated alluvial aquifers was calculated using ArcMap 10.3. To quantify channel transmission losses and determine the effects on regional water resources, three approaches using the Pitman model were applied. The three approaches include an explicit transmission loss function, the use of a wetland function to represent channel-floodplain storage exchanges and the use of a ‘dummy’ reservoir to represent floodplain storage and evapotranspiration losses. Results indicate that all three approaches were able to simulate channel transmission losses, although with differing magnitudes. Observed monthly flow data were used to as a means of validating loss simulations however for each sub-basin, medium and low flows were over-simulated which accounts for water uses that were inefficiently represented due to lack of data. Knowledge of the structure of the transmission loss function dictates that it is better at representing the dynamics of channel transmission losses, as it takes into account the contribution of losses to groundwater recharge whereas the other two functions simply store water and release it back to the channel. Overall, the hydrological modelling results demonstrate the potential of each approach in reproducing the dynamics of channel transmission losses between channel and alluvial aquifer within an existing sub-basin scale hydrological model. It is believed that better quantification of losses and more efficient qualitative determination of the function which best represents transmission losses, can be attained with more reliable observed data. In conclusion, a study of this nature can be beneficial to water resource estimation programmes as it highlights the uncertainties related with quantifying channel transmission loss processes in a semi-arid environment.
28
Carini, Giovannella y n/a. "Effects of Contemporary and Historical Processes on Population Genetic Structure of Two Freshwater Species in Dryland River Systems (Western Queensland, Australia)". Griffith University. Australian School of Environmental Studies, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050113.081250.
Texto completoResumen
Arid and semiarid river systems in Western Queensland, Australia, are characterized by the unpredictable and highly variable nature of their hydrological regimes as a result of the episodic nature of rain events in the region. These dryland rivers typically experience episodic floods and extremely low or no flow periods. During low or no flow periods, water persists only in relatively wide and deep sections of the river channels, which are called 'waterholes'. These isolated waterholes serve as refugia for aquatic species during protracted intervals between floods. In such discontinuous riverine habitat, dispersal of freshwater species may be achieved only during wet seasons, when water is flowing in rivers and the nearby floodplains. Obligate aquatic species occur in habitats that represent discrete sites surrounded by inhospitable terrestrial landscapes. Thus, movements are very much limited by the physical nature and arrangement of the riverine system. In addition, the distribution of a species may be also largely dependent on historical events. Landscape and river courses continually change over geological time, often leaving distinct phylogenetic 'signatures', useful in reconciling species' biology with population connectivity and earth history. The main aim of this study was to resolve the relative importance of contemporary and historical processes in structuring populations of two freshwater species in Western Queensland river systems. To address this aim, a comparative approach was taken in analysing patterns of genetic variation of two freshwater invertebrates: a snail (Notopala sublineata) and a prawn (Macrobrachium australiense). Mitochondrial sequences were used for both the species. In addition, allozyme and microsatellites markers were employed for N. sublineata. These species have similar distributions in Western Queensland region, although N. sublineata appears to be extinct in some catchments. M. australiense is thought to have good dispersal abilities due to a planktonic larval phase in its life cycle and good swimming capabilities, whereas N. sublineata is thought to have limited dispersal abilities, because of its benthic behaviour and because this species is viviparous. It was hypothesised that these freshwater invertebrates, would display high levels of genetic structure in populations, because physical barriers represented by terrestrial inhospitable habitat, are likely to impede gene flow between populations inhabiting isolated river pools. Genetic data for the two species targeted in this study supported this hypothesis, indicating strong population subdivision at all spatial scales investigated (i.e. between and within catchments). This suggests that contemporary dispersal between isolated waterholes is relatively restricted, despite the potential good dispersal abilities of one of the species. It was hypothesised that levels of gene flow between populations of aquatic species were higher during the Quaternary (likely movements of individuals across catchment boundaries) and that they have been isolated relatively recently. There is evidence that historically gene flow was occurring between populations, suggesting that episodic dispersal across catchment boundaries was likelier in the past. Episodic historical movements of aquatic fauna were facilitated by higher patterns of river connectivity as a result of the climate changes of the Pleistocene. Because the two species targeted in this study exhibit analogous spatial patterns of evolutionary subdivision it is likely that they have a shared biogeographic history. The unpredictable flow regime of rivers in Western Queensland is likely to have considerable effects on the genetic diversity of aquatic populations. First, if populations of obligate freshwater organisms inhabiting less persistent waterholes are more likely to experience periodic bottlenecks than those inhabiting more persistent ones, they would be expected to have lower levels of genetic diversity. Second, if populations inhabiting less persistent waterholes periodically undergo local extinction with subsequent recolonisation, there should be higher levels of genetic differentiation among them, due to the founder effects, than among those populations inhabiting more persistent waterholes. Contrary to the first prediction, the observed levels of genetic diversity in both N. sublineata and M. australiense were high in both more persistent and less persistent waterholes. There was no tendency for genetic diversity to be lower in less persistent than in more persistent waterholes. However, when Cooper waterholes were ranked in order of persistence, positive correlation between water persistence time in waterholes and genetic diversity was detected in N. sublineata but not in M. australiense. Contrary to the second prediction, highly significant genetic differentiation was found among populations from both less persistent and more persistent waterholes. This indicates that not only populations from less persistent but also those from more persistent waterholes were very dissimilar genetically. This study demonstrated the importance of both contemporary and historical processes in shaping the population structure of obligate freshwater species in Western Queensland river systems. It has indicated that contemporary movements of freshwater species generally are extremely limited across the region, whereas episodic dispersal across catchment boundaries was possible during the Pleistocene, due to different patterns of river connectivity.
29
Carini, Giovannella. "Effects of Contemporary and Historical Processes on Population Genetic Structure of Two Freshwater Species in Dryland River Systems (Western Queensland, Australia)". Thesis, Griffith University, 2004. http://hdl.handle.net/10072/367070.
Texto completoResumen
Arid and semiarid river systems in Western Queensland, Australia, are characterized by the unpredictable and highly variable nature of their hydrological regimes as a result of the episodic nature of rain events in the region. These dryland rivers typically experience episodic floods and extremely low or no flow periods. During low or no flow periods, water persists only in relatively wide and deep sections of the river channels, which are called 'waterholes'. These isolated waterholes serve as refugia for aquatic species during protracted intervals between floods. In such discontinuous riverine habitat, dispersal of freshwater species may be achieved only during wet seasons, when water is flowing in rivers and the nearby floodplains. Obligate aquatic species occur in habitats that represent discrete sites surrounded by inhospitable terrestrial landscapes. Thus, movements are very much limited by the physical nature and arrangement of the riverine system. In addition, the distribution of a species may be also largely dependent on historical events. Landscape and river courses continually change over geological time, often leaving distinct phylogenetic 'signatures', useful in reconciling species' biology with population connectivity and earth history. The main aim of this study was to resolve the relative importance of contemporary and historical processes in structuring populations of two freshwater species in Western Queensland river systems. To address this aim, a comparative approach was taken in analysing patterns of genetic variation of two freshwater invertebrates: a snail (Notopala sublineata) and a prawn (Macrobrachium australiense). Mitochondrial sequences were used for both the species. In addition, allozyme and microsatellites markers were employed for N. sublineata. These species have similar distributions in Western Queensland region, although N. sublineata appears to be extinct in some catchments. M. australiense is thought to have good dispersal abilities due to a planktonic larval phase in its life cycle and good swimming capabilities, whereas N. sublineata is thought to have limited dispersal abilities, because of its benthic behaviour and because this species is viviparous. It was hypothesised that these freshwater invertebrates, would display high levels of genetic structure in populations, because physical barriers represented by terrestrial inhospitable habitat, are likely to impede gene flow between populations inhabiting isolated river pools. Genetic data for the two species targeted in this study supported this hypothesis, indicating strong population subdivision at all spatial scales investigated (i.e. between and within catchments). This suggests that contemporary dispersal between isolated waterholes is relatively restricted, despite the potential good dispersal abilities of one of the species. It was hypothesised that levels of gene flow between populations of aquatic species were higher during the Quaternary (likely movements of individuals across catchment boundaries) and that they have been isolated relatively recently. There is evidence that historically gene flow was occurring between populations, suggesting that episodic dispersal across catchment boundaries was likelier in the past. Episodic historical movements of aquatic fauna were facilitated by higher patterns of river connectivity as a result of the climate changes of the Pleistocene. Because the two species targeted in this study exhibit analogous spatial patterns of evolutionary subdivision it is likely that they have a shared biogeographic history. The unpredictable flow regime of rivers in Western Queensland is likely to have considerable effects on the genetic diversity of aquatic populations. First, if populations of obligate freshwater organisms inhabiting less persistent waterholes are more likely to experience periodic bottlenecks than those inhabiting more persistent ones, they would be expected to have lower levels of genetic diversity. Second, if populations inhabiting less persistent waterholes periodically undergo local extinction with subsequent recolonisation, there should be higher levels of genetic differentiation among them, due to the founder effects, than among those populations inhabiting more persistent waterholes. Contrary to the first prediction, the observed levels of genetic diversity in both N. sublineata and M. australiense were high in both more persistent and less persistent waterholes. There was no tendency for genetic diversity to be lower in less persistent than in more persistent waterholes. However, when Cooper waterholes were ranked in order of persistence, positive correlation between water persistence time in waterholes and genetic diversity was detected in N. sublineata but not in M. australiense. Contrary to the second prediction, highly significant genetic differentiation was found among populations from both less persistent and more persistent waterholes. This indicates that not only populations from less persistent but also those from more persistent waterholes were very dissimilar genetically. This study demonstrated the importance of both contemporary and historical processes in shaping the population structure of obligate freshwater species in Western Queensland river systems. It has indicated that contemporary movements of freshwater species generally are extremely limited across the region, whereas episodic dispersal across catchment boundaries was possible during the Pleistocene, due to different patterns of river connectivity.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Full Text
30
Niu, Jun y 牛俊. "A comprehensive analysis of terrestrial hydrological processes over the Pearl River basin in South China". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45587462.
Texto completo
31
McEwan, Robert. "Interdisciplinary study of hydrodynamic and biogeochemical processes of a large-scale river plume". Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1551.
Texto completoResumen
This research has utilised the Massachusetts Institute of Technology gen- eral circulation model (MITgcm) along with observations taken as part of the River In uences on Shelf Ecosystems (RISE) study to investigate the dynamic processes associated with the Columbia River plume at different temporal and spatial scales. Firstly, a high resolution ( x= y=25 m) investigation of the near-field plume was undertaken using the fully non-hydrostatic mode of the MITgcm. This resulted in the reproduction of a detailed inner plume as well as a series of radiated internal waves. In addition to first mode internal waves, second order waves were radiated from the plume boundary when propagation ve- locity becomes sub-critical. Third mode internal waves were also observed, trapped at the plume head. The fine plume structure produced revealed sec- ondary fronts within the plume that also generated internal waves. These features increase the mixing occurring inside the plume, resulting in greater entrainment of underlying waters into the plume. The use of Lagrangian drifters within the model produced detailed results of the recirculation tak- ing place within the emerging plume and how this recirculation changes with depth. This has implications for the near-field recirculation of biologically important solutes present in the plume waters. A second coarser resolution horizontal grid ( x= y=500 m) was imple- mented to investigate the processes of the large-scale plume with the addi- tion of wind forcing. Experiments with both simplified and realistic wind scenarios were carried out and comparisons with in-situ data were made. This revealed the dominance of wind effects on the outer plume and tidal effects on the inner plume. In the simplified wind cases, the classical the- ory of plume propagation under the action of upwelling and downwelling favourable winds was recreated. For the case of realistic winds, there was some success in reproducing a hindcast of the plume location. Tracer fields were used to represent nutrient concentrations based on observed data. Whilst these results showed variations from observations, they did allow a spatially and temporally complete view to be taken of nutrient distribu- tion in the region.
32
Bicudo, Tacio Cordeiro. "Estudo da formação da bacia hidrográfica do rio Amazonas através da modelagem numérica de processos tectônicos e sedimentares". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/14/14132/tde-04062018-143103/.
Texto completoResumen
A bacia hidrográfica do rio Amazonas abrange uma área de 6 × 106 km2 da região norte da América do Sul. O seu canal mais longo, com quase 7.000 km tem origem nos Andes peruanos e cruza todo o continente até chegar na foz, no Atlântico Equatorial. Apesar dos diversos esforços científicos, os processos que guiaram a evolução da paisagem na Amazônia ainda são discutidos, assim como a data do estabelecimento dessa grande bacia hidrográfica que culminou com a forma¸cao do rio Amazonas como um rio transcontinental. O presente trabalho teve como objetivo estudar como se deu a evolução da paisagem na regiao norte da América do Sul, com foco na forma¸cao do Rio Amazonas, através de simulações usando um modelo numérico que incorpora orogenia, flexura, isostasia da litosfera, clima e processos superficiais de erosao e sedimentação. Diversos experimentos numéricos foram realizados alterando-se a topografia original, taxa de espessamento crustal nos Andes, erodibilidade das rochas, entre outros parâmetros. Constatou-se que o instante da formação do rio transcontinental é muito sensível a modificações na paleotopografia inicial do modelo e erodibilidade das rochas. Porém, em todos os modelos, o instante da formação do rio Amazonas ´e marcado por um aumento expressivo na taxa de sedimentação na foz do rio Amazonas e uma correspondente queda no aporte sedimentar na foz do rio Orinoco. Adicionalmente, um aumento na taxa de espessamento crustal na região andina não modifica expressivamente as taxas de sedimentação na foz do Amazonas. Isso ocorre pois o aumento no aporte sedimentar proveniente do Andes é essencialmente depositado nas bacias de ante-país devido ao aumento no espaço de acomodação gerado pela carga adicional sobre a placa litosférica. O aumento da taxa de precipitação sobre a cordilheira dos Andes se reflete em um aumento nas taxas de deposição nas bacias de ante-país, na Bacia do Solimões e na foz do Orinoco, porém na foz do Amazonas as taxas de sedimentação sofrem um crescimento pouco expressivo. Já um aumento na precipitação sobre todo o modelo faz com que, em todas as bacias sedimentares, as taxas de sedimentação sofram um aumento gradativo.The Amazon hydrographic basin is the largest in the world, covering 6 × 106 km2 of northern South America. Its longest channel, with almost 7000 km, brings sediment from the Andes to the Atlantic Ocean, in brazilian equatorial coast. Despite the scientific efforts, the timing of origin of this hydrographic basin is still debated, as well as the processes that guided its evolution and shaped the landscape in this region. In my research, I used an adaptation of the numerical model developed by Sacek (2014) to study the landscape evolution of the north of South America, focusing on the establishment of the Amazon River as a transcontinental river. The numerical model accounts for the contributions of orogeny, climate, isostasy and flexure of the lithosphere, and surface processes (erosion and deposition of sediments). I performed dozens of experiments, testing a range of values for the different parameters of the model, and I was able to reproduce, in many aspects, the evolution of landscape in the region, as hypothesized by others researchers. I also observed in my results a changing in drainage pattern, that corresponds to the onset of the Amazon River. Furthermore, it was predicted by the simulations, at the moment of the onset of the Amazon River, a great increase in sedimentary deposition at the Amazon Fan, simultaneously with a fall in sedimentary deposition at the Orinoco mouth. However, in the simulations, the moment of the onset of the Amazon River is very sensitive to changes in the initial topography of the model. I also tested the influence of crustal thickening rate in the Andes, precipitation rate, and resistance to erosion of sediments of the model, in the sedimentation pattern of the region. I concluded that an increase in precipitation rate in the model can significantly alter the rate of deposition at the region of Amazons mouth and in others sedimentary basins in the model. However, an increase in crustal thickening or precipitation rate in the Andes does not expressively change the rate of deposition at the region of Amazons mouth, but changes occur at foreland basins and at Solimoes Basin.
33
Marda, Saurabh. "Effect of Ozonation and BAC Filtration Processes on Monochloramine Demand". Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/10577.
Texto completoResumen
Although the kinetics and mechanism of monochloramine decay in organic-free waters are relatively well understood, those in natural waters are not, due to exceedingly complex and poorly defined interactions of monochloramine with natural organic matter (NOM) and particles. Ozonation followed by a biologically activated carbon (BAC) filtration is a commonly practiced process option that affects the characteristics of both dissolved and particulate constituents in the water. However, how these changes in water constituents affect stability of the residual disinfectant, or monochloramine in particular, are currently unknown. Kinetics of monochloramine decay in water samples obtained before and after ozonation and BAC treatments were performed under varying operating conditions were determined by bench-scale batch experiments. Stability of monochloramine in the BAC filter effluent samples obtained at different times after backwashing was determined. It was found that in most cases monochloramine stability was greatly decreased after BAC filtration. Further filtering the BAC effluents with 1.2 and #61549;m polycarbonate membrane resulted in a substantial increase in monochloramine stability. A further increase was observed after filtering the samples using a 0.4 m membrane. This finding suggested that particulate matter generated from the filters could be the major cause of monochloramine instability. The fines from the activated carbon, possible components of the particulate matter eluting from the BAC filters, were found to exert an insignificant monochloramine demand both in the presence and absence of NOM, which is contrary to previous speculation in the literature about their demand for monochloramine. While there appears to exist a relationship between chloramine demand and HPC count of the filter effluent, more research will be needed to determine the effect of nature and type of microorganisms and their byproducts have on chloramine demand. Effect of ozonation on monochloramine stability is also under investigation using both the water sampled from full-scale plant and the synthetic water prepared with Suwannee River NOM.
34
Waltner, Mason. "Quantifying Legacy Sediment in the Upper Charles River Watershed, Massachusetts". Thesis, Boston College, 2016. http://hdl.handle.net/2345/bc-ir:108052.
Texto completoResumen
Thesis advisor: Noah SnyderWhile it has been shown that extensive sedimentation in historic millponds has greatly affected streams in the Mid-Atlantic Piedmont region (Walter and Merritts, 2008), much less is known about the phenomenon in the heavily dammed areas of post-glacial New England. Some research has found similar deposits behind breached historic dams in the Sheepscot River watershed in mid-coast Maine, but at a smaller scale than those seen in the Mid-Atlantic region (Strouse, 2013; Hopkins, 2014). I attempt to further explore millpond sedimentation in New England by quantifying the volume of millpond sediment, also called legacy sediment, in the 171.3 km² upper Charles River watershed in eastern Massachusetts. Twenty three milldams were located in the watershed on 1850s maps, giving a damming density of 0.177 dams/km². Each historic dam that had since breached, 14 in total, was visited in the field to identify possible legacy sediment deposits. Legacy sediments were identified by their meter or higher terraces made of fine sands and silt and verified by comparison to sedimentary patterns found in other legacy sediment deposits and radiocarbon dating of material both within the legacy sediment and in the underlying layer. Legacy sediment terraces with an area of 1.68*10⁴ m² and a total volume of 1.29 - 2.57*10⁴ m³ were found upstream of two adjacent breached historic dam sites on the Charles River in Medway, MA. Radiocarbon dates from a coarse sand and gravel lower at 1.8 m depth returned pre-settlement dates of 1281-1391 cal AD (two σ). These dams were immediately downstream of a large glacial feature with steep banks along the river. The lack of legacy sediment at other dam sites and the lack of sedimentation behind intact dams suggest that a low sediment supply to millponds prevented legacy sediment deposits from forming in most of the watershed
Thesis (BS) — Boston College, 2016
Submitted to: Boston College. College of Arts and Sciences
Discipline: Departmental Honors
Discipline: Earth and Environmental Sciences
35
Schneider, Suzanne Zvalaren Willey Joan D. "Mercury sources and cycling processes in the Cape Fear River estuary, North Carolina". Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2906.
Texto completoResumen
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2010.Title from electronic title page (viewed Jun. 23, 2010). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Marine Sciences." Discipline: Marine Sciences; Department/School: Marine Sciences.
36
Cohn, Teresa Helene. "Settlement, identity and environment: understanding processes of vegetation change along the Wind River". Diss., Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/cohn/CohnT1210.pdf.
Texto completoResumen
Contemporary research concerning wildlands and wildlife of the American West increasingly calls for greater complexity in understanding human-environmental relationships. This dissertation investigates a culturally diverse portion of Greater Yellowstone in order to complicate these dialogues. It explores a riparian corridor along the Wind River, a region permanently settled by Eastern Shoshone, Northern Arapaho and Euro-American residents in the late 1800s and early 1900s. Using the Wind River Basin as a case study, this research observes the landscape through three different lenses: settlement geography, place identity, and vegetation change. By incorporating a variety of methods to understand regional change (including historical research, interviews with residents, and comparative aerial and ground photography), it finds that riparian change relates to a complex cultural-ecological mosaic. Not only is change perceived differently by a variety of communities in the Wind River Basin; change relates to century-old settlement geographies, government policies and cultural preferences, shifting economies and power relationships, and evolving relationships formed by interrelationships of people and environment. This dissertation argues that investigations of environmental change must not oversimplify dynamic relationships between people and place. Indeed, the complexity of these places may relate to why Greater Yellowstone has remained one of the largest intact ecosystems in the lower 48 states.
37
Wu, Yiping y 吴一平. "Investigation of integrated terrestrial processes over the East River basin in South China". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43085799.
Texto completo
38
Hubbard, Christopher George. "Acid mine drainage generation and transport processes in the Tinto River, SW Spain". Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440101.
Texto completo
39
Hortobágyi, Borbála. "Multi-scale interactions between riparian vegetation and hydrogeomorphic processes (the lower Allier River)". Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAL001/document.
Texto completoResumen
Dans les écosystèmes, tels que les rivières, les marais salés, les mangroves, les dunes côtières, qui sont exposés à des flux hydrogéomorphologiques fréquents et réguliers (c’est-à-dire à des perturbations physiques), des rétroactions se mettent en place entre la géomorphologie (eau, sédiments et formes fluviales) et les plantes (par exemple Populus nigra L., Salix alba L., Salix purpurea L. dans les rivières). L’établissement de la végétation est contrôlé par des processus hydrogéomorphologiques qui, en retour, sont modulés par la végétation. De telles rétroactions contrôlent la dynamique des écosystèmes riverains. Dans cette thèse, nous avons abordé deux questions principales afin de mieux comprendre les rétroactions entre la végétation riveraine et les processus hydrogéomorphologiques : (i) comment la végétation riveraine répond-elle aux contraintes hydrogéomorphologiques ? (ii) comment et dans quelle mesure les plantes ingénieures, une fois établies, affectent-elles la géomorphologie fluviale ? Nous avons étudié ces questions sur la rivière Allier (France) à travers une approche emboîtée multi-échelles allant de l’échelle du patron paysager au trait de plante. Nous avons testé l’applicabilité de la méthode de photogrammétrie pour quantifier la réponse et l’effet de la végétation riveraine et des rétroactions biogéomorphologiques à différentes échelles spatio-temporelles (corridor, banc alluvial et individu). À l’échelle du corridor, nous avons recherché la signature topographique de la végétation riveraine dans le paysage, en utilisant des données photogrammétriques et LiDAR. À l’échelle intermédiaire du banc alluvial, nous avons étudié l’aptitude des trois espèces pionnières dominantes riveraines de Salicaceae (P. nigra, S. purpurea, S. alba) à s’établir et à agir comme ingénieurs d’écosystème en piégeant les sédiments fins. À l’échelle la plus fine du trait de plante, nous avons quantifié la relation existante entre les attributs de trait de réponse des jeunes plantes de P. nigra et leur exposition à trois niveaux différents de stress mécanique (tête de banc fortement exposée, queue de banc moins exposée, chute alluviale). Nous avons identifié les difficultés et les erreurs à ne pas commettre pour appliquer correctement la photogrammétrie dans les études des rétroactions biogéomorphologiques. En tout état de cause, la photogrammétrie s’est avérée être un outil performant pour quantifier un ensemble de paramètres pertinents pour répondre à des questions de recherche fondamentale aux trois échelles spatiales considérées. À l’échelle la plus large, la signature topographique de la végétation est particulièrement difficile à identifier en raison de la dynamique complexe des formes fluviales de la rivière Allier. Cependant, en concentrant les observations sur des zones de taille réduite et fortement connectées (bancs alluviaux bordant le chenal), la signature de la végétation a pu être identifiée par cette méthode. Elle semble augmenter avec la croissance de la hauteur végétale (progression temporelle de la succession biogéomorphologique), ce qui est en accord avec le modèle de succession biogéomorphologique fluviale (SBF). À l’échelle intermédiaire du banc alluvial, les rétroactions biogéomorphologiques pouvaient être bien identifiées. La capacité des plantes riveraines à s’établir et à agir comme ingénieurs d’écosystème dépend à la fois des espèces et de leur physionomie, de leur âge et de leur position respective sur les bancs alluviaux. À l’échelle la plus fine de l’individu, nous avons capturé la réponse morphologique et biomécanique contrastée de P. nigra à l’exposition aux différents niveaux de contrainte mécanique d’un point de vue de trait. Dans tous les niveaux hiérarchiques, des rétroactions biogéomorphologiques liées aux échelles ont été détectées et synthétisées dans un modèle conceptuel. [...]N ecosystems, such as rivers, salt marshes, mangroves, coastal dunes which are exposed to frequent and regular hydrogeomorphic fluxes (i.e. physical disturbances), feedbacks between geomorphology (water, sediment and landforms) and plants (e.g. Populus nigra L., Salix alba L., Salix purpurea L. in rivers) can occur. Vegetation esta¬blishment is controlled by hydrogeomorphic processes which in turn are modulated by vegetation. Such feedbacks control riparian ecosystem dynamics. In this thesis, we addressed two main questions in an effort to better understand feedbacks between riparian vegetation and hydrogeomorphic processes: (i) How does riparian vegetation respond to hydrogeomorphic constraints? (ii) How, and to what extent, do established engineer plants affect fluvial geomorphology? We studied these questions through a nested multi-scale approach from landscape pattern to plant trait scales on the dynamic wandering Allier River (France). We tested the applicability of the method of photogrammetry to quantify the response and the effect of riparian vegetation and biogeomorphic feedbacks at different spatio-temporal scales (i.e. corridor, alluvial bar and individual). At the corridor scale, we searched for the topographic signature of riparian vegetation in the landscape, using photogrammetric and LiDAR data. At the intermediate alluvial bar scale, we investigated the aptitude of three dominant pioneer riparian Salicaceae species (P. nigra, S. purpurea and S. alba) to establish and to act as ecosystem engineers by trap¬ping fine sediment. At the finest, plant trait scale, we quantified the relation between response trait attributes of young P. nigra plants and their exposure to three different levels of mechanical stress (a highly exposed bar-head, a less exposed bar-tail, a chute channel). We identified some difficulties or failures to properly apply photogrammetry in biogeomorphic feedback studies. However, photogrammetry appeared as a useful tool to quantify a set of relevant parameters to respond to fundamental research questions concerning biogeomorphic feedbacks at the three nested spatial scales. At the broadest, the topographic signature of vegetation was not easy to capture because of the complex shifting mosaic of landforms of the Allier River. However, by focusing on more connec¬ted, restricted areas (i.e. alluvial bars), the signature of vegetation could be captured. It seems to increase with increasing vegetation height corresponding to the evolutionary phases of the fluvial biogeomorphic succession (FBS) model. At the intermediate, alluvial bar scale, biogeomorphic feedbacks could be well identified. The capacity of riparian plants to establish and act as ecosystem engineers depended both on species and their physiognomy, their age and their location on alluvial bars. At the finest, individual plant scale, we captured the contrasting morphological and biomechanical response of P. nigra to variable mechanical stress exposure from a trait perspective. In all hierarchical levels, scale-related biogeomorphic feedbacks were detected and described in a conceptual model. The three scales were considered as cycles composed of four different phases, which can have a variable temporality. The broadest spatio-temporal scale represents the evolution over several decades of the landscape mosaic resulting from the balance between constructive (vegetation establishment, growth and succession) and destruc¬tive (floods) forces. [...]
40
Grove, James Robin. "Downstream change in the processes of riverbank erosion along the River Swale, UK". Thesis, University of Birmingham, 2001. http://etheses.bham.ac.uk//id/eprint/4429/.
Texto completoResumen
This study was designed to test the hypothesis that riverbank erosion processes altered with increasing distance from a river source. The River Swale, northern England, was monitored at nine sites throughout its 109-km length, from December 1995 – March 1998. Erosion pins, bank-edge surveying, and Photo-Electronic Erosion Pins (PEEPs) were used to determine rates and timings of erosion. The rates were compared against a range of environmental variables based on temperature, river stage, and precipitation at 14-day intervals for erosion pins and 15-minute intervals for PEEPs. This allowed processes of erosion to be inferred. Catchment erosion rates were modelled using quadratic equations, simulating a mid-basin peak of 3.58 m a\(^{-1}\). Rates of erosion were low upstream, 0.07 m a\(^{-1}\), and also downstream, 0.12 m a\(^{-1}\). Subaerial processes, especially frost action, dominated upstream. Fluvial entrainment was most influential mid-catchment. Mass failures were most efficient downstream, but were more frequent mid-catchment. Piping, sapping and cantilever failures did not follow the same trends and were modelled separately. The length of the erosion season increased downstream as the number of active processes increased.
41
Carpenter, Deborah A. "Testing the river continuum concept exploring ecological processes in the Wheeling Creek Watershed /". Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=1879.
Texto completoResumen
Thesis (M.A.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains v, 75 p. : ill., maps (some col.). Includes abstract. Includes bibliographical references (p. 53-57).
42
Josko, Troselj. "FLUVIAL INFLUENCE ON ESTUARINE SEDIMENT TRANSPORT PROCESSES AND LINKAGE OF ITS OUTFLOW DATA TO COASTAL MODELING". Kyoto University, 2016. http://hdl.handle.net/2433/217745.
Texto completo
43
Arbuthnott, Alison Gail. "An investigation into the effects of catchment processes on the water quality of southern chalk rivers". Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367967.
Texto completoResumen
The physical, chemical and biological characteristics of five southern English chalk streams in neighbouring catchments were investigated seasonally over two years. At the catchment scale, the five chalk rivers had very similar physio-chemical properties. Differences between years and between seasons were much greater than those between rivers or within-river longitudinal differences. Elevated inorganic nutrient concentrations, relative to reportedly 'pristine' systems, indicated some degree of catchment water quality deterioration in all five rivers. The effect of physical habitat degradation (channel overwidening and sedimentation) on river biota was investigated at a within-river, reach scale. The increased proportion of fine sediment within the coarse gravel substratum had a marked effect on invertebrate communities. Overwidening, however, was found to have little impact over the two years. Communities showed a high degree of stability between years, and between individual catchments, reflecting the high overall biological stability of these aquifer-fed river systems. Habitat manipulation experiments at the within-reach scale demonstrated the importance of substratum characteristics to macroinvertebrate communities. Invertebrate colonisation of newly exposed substrata over time was quantitatively and qualitatively different for coarse and fine particles - a function of shifting resource utilisation and microhabitat preferences. The relatively long time taken to fully colonise new substrata demonstrated the weak ability of chalk stream invertebrate communities to respond rapidly to changes in habitat, reflecting the stable physical nature of natural chalk streams and the vulnerability of their communities to anthropogenic disturbance.
44
Young, Adam. "Sediment Processes Influencing the Coastline of Kouchibouguac National Park, New Brunswick". Thesis, Fredericton: University of New Brunswick, 2012. http://hdl.handle.net/1882/35658.
Texto completoResumen
Parks Canada focuses its tourism and conservation efforts in Kouchibouguac National Park along the park's diverse coastline made up of a variety of sensitive ecosystems including salt marshes, stream estuaries and a shifting barrier island lagoon system. The dynamic sediment processes in the park are not fully understood, making it difficult for Parks Canada to make informed decisions as sea-level rise in the region accelerates. In this study, extensive field data were collected in two sediment zones bordering the Kouchibouguac Lagoon. Stream data were collected and used to estimate the monthly average sediment load entering the lagoon. The maximum and minimum monthly average sediment loads were 130 g/s and 11 g/s in April and September, respectively. These freshwater sediments pass through estuaries to deposit at the coastline of the park.
Changes in the barrier system surrounding the tidal inlet Little Gully were also monitored over 15 months using modern surveying techniques. The surveys showed a general southward shift in the study area and a landward migration of sediments within the flood tidal delta of the inlet. Dune surface area, volume, and vegetation cover were also examined, and the critical shear stress and velocity of the sediments were calculated. The field investigations revealed that the Kouchibouguac Lagoon was gradually filling in with sediments during the study. It is recommended that a permanent hydrometric station be installed in one of the major streams in the park and that future research along the coastline of the park complement Parks Canada's current monitoring program for the barrier island system.
45
Duffy, B. "Phase transfer processes affecting the chemistry of iron and manganese in river-estuary systems". Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356766.
Texto completo
46
Colvin, Jessica. "Site Formation Processes and Bone Preservation Along the Trinity River Basin, North Central Texas". Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc500040/.
Texto completoResumen
This thesis presents the results of geoarchaeological investigations of several archaeological sites along the Elm Fork of the Trinity River in north central Texas. Archaeological data recorded from mitigation excavations in Denton and Cooke counties were analyzed to understand the geologic impacts on faunal preservation resulting from site formation processes. The faunal assemblages are highly fragmented, even in settings known for good preservation. A combined approach using geoarchaeological and taphonomic techniques was implemented to examine how fragmentation, evidence of soil weathering, and differential preservation were impacted by differing geologic conditions throughout the river basin. Intrasite and intersite results of the sites show that a great deal of variability of faunal preservation is present at difference scales of analysis.
47
Davis, Edgar V. "Circulation and transport processes for the Pocomoke River a tributary to partially mixed estuary /". College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3264.
Texto completoResumen
Thesis (M.S.) -- University of Maryland, College Park, 2005.Thesis research directed by: Marine, Estuarine, Environmental Sciences Graduate Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
48
Mulungu, Deogratias Maganga Mohamed. "Development of a physically based model of hydrological processes in forested mountainous river basins". 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/148847.
Texto completo
49
Vericat, Querol Damià. "Sediment transport and processes in a highly regulated river. The lower Ebro, NE Iberian Peninsula". Doctoral thesis, Universitat de Lleida, 2005. http://hdl.handle.net/10803/8231.
Texto completoResumen
Aquesta tesi estudia el transport de sediment i els processos fluvials associats al tram baix del riu Ebre al llarg de dos anys hidrològicament mitjans (2002-2004). El transport de sediment, que inclou tant la càrrega de fons com el sediment en suspensió, s'ha mesurat aigües amunt i avall del complex d'embassaments Mequinenza-Riba-roja-Flix. Els canvis morfològics i granulomètrics s'han analitzat aigües avall de la presa de Flix. La càrrega mitjana anual de sediment aigües amunt de les preses és de 1,64·106 tones, de les quals un 99% ho són en suspensió. El transport mig anual aigües avall dels embassaments és de 0,45·106 tones (60% en suspensió i 40% com a càrrega de >fons). Els embassaments retenen al voltant del 95% de la càrrega transportada en suspensió. El transport mitjà anual aigües avall de la presa de Flix representa el 3% del que el riu transportava a l'inici del segle XX en absència d'embassaments. La major part del sediment que el riu transporta actualment prové, per tant, de la pròpia llera, fet que causa una incisió mitjana anual d'uns 30 mm. Una part molt important de la càrrega transportada anualment es produeix durant avingudes d'alta magnitud. Per exemple, el transport aigües amunt de les preses durant les crescudes de febrer i març de 2003 (Q10, 2.600 m3/s) va ser de 1.700.000 tones de sediment. La concentració mitjana de sediment en suspensió durant aquests episodis va ser de 0,5 g/l i la taxa mitjana de càrrega de fons de 100 g/ms. El sediment transportat com a càrrega de fons va representar un 1,5% del total del sediment transportat. Aigües avall de la presa de Flix el riu va transportar 175.000 tones de sediment durant les mateixes crescudes, la meitat com a càrrega de fons. La concentració mitjana de sediment en suspensió fou de 0,05 g/l i la taxa mitjana de càrrega de fons va ser de 150 g/ms. Ambdós modes de transport tenen una gran variabilitat temporal i espacial. La distribució granulomètrica del material del llit està directament controlada per la competència del flux i per la disponibilitat de sediment. Les crescudes d'alta magnitud de 2002-2003 van mobilitzar la cuirassa superficial, incrementant la disponibilitat de sediment (material subsuperficial) i causant una notable incisió de la llera. Contràriament, durant el 2003-2004 el cabal no fou suficientment competent per mobilitzar les fraccions més grolleres i, conseqüentment, el procés dominat fou el de re-acuirassament del llit del riu. Ambdós anys mostren un cicle complert de incisió-acuirassament. Els canvis en la morfologia fluvial aigües avall de la presa de Flix durant la segona meitat del segle XX mostren la pèrdua d'àrees sedimentàries actives (disponibilitat de sediment) degut a la colonització per la vegetació de ribera, i la disminució de l'amplada de la llera (20%), reduint, conseqüentment, la secció activa d'aquesta. La manca de sediment i la reducció de les crescudes controlen els canvis en la morfologia fluvial a mig i llarg termini.Esta tesis estudia el transporte de sedimento y los procesos fluviales asociados en el tramo bajo del río Ebro durante dos años hidrológicamente medios (2002-2004). El transporte de sedimento, que incluye tanto la carga de fondo como el sedimento en suspensión, se ha muestreado aguas arriba y abajo del complejo de embalses Mequinenza-Ribarroja-Flix. Los cambios morfológicos y granulométricos se han analizado aguas abajo de la presa de Flix. La carga media anual de sedimento aguas arriba de las presas es de 1,64·106 toneladas, de las cuales un 99% lo son en suspensión. El transporte medio anual aguas abajo de los embalses es de 0,45·106 toneladas (60% en suspensión y 40% como carga de fondo). Los embalses retienen alrededor del 95% de la carga en suspensión. El transporte medio anual aguas abajo de la presa de Flix representa el 3% de lo que el río transportaba al principio del siglo XX en ausencia d'embalses. La mayor parte del sedimento que el río transporta actualmente proviene, por lo tanto, del propio cauce, hecho que causa una incisión media anual de 30 mm. Una parte muy importante de la carga transportada anualmente lo es durante avenidas de alta magnitud. Por ejemplo, el transporte aguas arriba de las presas durante las crecidas de febrero y marzo de 2003 (Q10, 2.600 m3/s) fue de 1.700.000 toneladas de sedimento. La concentración media de sedimento en suspensión durante estos episodios fue de 0,5 g/l y la tasa media de carga de fondo de 100 g/ms. El sedimento transportado como carga de fondo representó un 1,5% del total del sedimento transportado. Aguas abajo de la presa de Flix el río transportó 175.000 toneladas de sedimento durante las mismas crecidas, la mitad como carga de fondo. La concentración media de sedimento en suspensión fue de 0,05 g/l y la tasa media de carga de fondo fue de 150 g/ms. Ambos modos de transporte tienen una gran variabilidad temporal y espacial. La distribución granulométrica del material del lecho está directamente controlada por la competencia del flujo y por la disponibilidad de sedimento. Las crecidas de alta magnitud de 2002-2003 movilizaron la coraza superficial, incrementando la disponibilidad de sedimento (material subsuperficial) y causando una notable incisión del cauce. Contrariamente, durante 2003-2004 el caudal no fue suficientemente competente para movilizar las fracciones más gruesas y, consecuentemente, el proceso dominante fue el de re-acorazamiento del lecho del río. Ambos años muestran un ciclo completo de incisión-acorazamiento. Los cambios en la morfología fluvial aguas abajo de la presa de Flix durante la segunda mitad del siglo XX muestran la pérdida de áreas sedimentarias activas (disponibilidad de sedimento) debido a la colonización por vegetación de ribera, y la disminución de la anchura del cauce (20%), reduciendo, como consecuencia, la sección activa. La falta de sedimento y la reducción de las crecidas controlan los cambios en la morfología fluvial a medio y largo plazo.
The sediment transport and the associated fluvial processes have been analysed in the large impounded lower Ebro River during two representative hydrological years (2002-2004). Sediment transport, including both suspended and bedload, have been measured upstream and downstream the Mequinenza-Riba-roja-Flix reservoirs chain. Fluvial adjustments have been monitored downstream from the Flix Dam. Results indicate that the mean annual total load upstream from the dams is estimated at 1.64·106 tonnes, of which more than 99% is transported in suspension. The mean annual total load below the dams is estimated at 0.45·106 tonnes, of which 60% is transported in suspension and 40% as bedload. Reservoirs retain up to 95% of fine sediments transported by the river. Total load represents 3% of what was transported at the beginning of the 20th century in the absence of dams. Nowadays, sediment load downstream from the dams is almost all entrained from the riverbed, causing a mean riverbed incision of 30 mm per year. Sediment transport was particularly high during floods. Around 1,700,000 tonnes were transported upstream from the dams during the February and March 2003 floods (Q10 with a peak discharge of 2,600 m3/s), with mean suspended sediment concentrations of 0.5 g/l and mean bedload rates of 100 g/ms. Bedload represented approximately 1.5% of the total load. In contrast, 175,000 tonnes were transported at the downstream monitoring section, with mean suspended sediment concentrations of 0.05 g/l and mean bedload rates of 150 g/ms, showing a high degree of temporal and spatial variability. Bedload represented approximately half of the total load. The grain-size distribution of the riverbed materials has shown to be strongly related to flow competence and sediment availability. On one side, high competent discharges during 2002-2003 were able to entrain most coarse surface material (i.e., armour layer), increasing the availability of sediment to be transported (subsurface material), causing remarkable incision. On the other, discharges during 2003-2004 were not competent to move coarse particles and a re-armouring process occurred. Both years, including five natural floods and two flushing flows, have shown a complete incision-armouring cycle. Riverchannel adjustments during the second half of the 20th century include the loss of active sedimentary areas, hence sediment availability, due to vegetation encroachment (i.e. riparian forest), and channel narrowing (20%), thus reducing the active section of the channel. The lack of sediment transport and the reduction of frequent floods below the dams control the medium and long-term changes observed in river's channel morphology.
50
Javernick, Luke Anthony. "Modeling flood-induced processes causing Russell lupin mortality in the braided Ahuriri River, New Zealand". Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2013. http://hdl.handle.net/10092/8972.
Texto completoResumen
The braided rivers and floodplains in the Upper Waitaki Basin (UWB) of the South Island of New Zealand are critical habitats for endangered and threatened fauna such as the black stilt. However, this habitat has degraded due to introduced predators, hydropower operations, and invasive weeds including Russell lupins. While conservation efforts have been made to restore these habitats, flood events may provide a natural mechanism for removal of invasive vegetation and re-creation of natural floodplain habitats. However, little is understood about the hydraulic effects of floods on vegetation and potential mortality in these dynamic systems. Therefore, this thesis analyzed the flood-induced processes that cause lupin mortality in a reach of the Ahuriri River in the UWB, and simulated various sized flood events to assess how and where these processes occurred.
To determine the processes that cause lupin mortality, post-flood observations were utilized to develop the hypothesis that flood-induced drag, erosion, sediment deposition, inundation, and trauma were responsible. Field and laboratory experiments were conducted to evaluate and quantify these individual processes, and results showed that drag, erosion, sediment deposition and inundation could cause lupin mortality. Utilizing these mortality processes, mortality thresholds of velocity, water depth, inundation duration, and morphologic changes were estimated through data analysis and evaluation of various empirical relationships.
Delft3D was the numerical model used to simulate 2-dimensional flood hydraulics in the study-reach and was calibrated in three stages for hydraulics, vegetation, and morphology. Hydraulic calibration was achieved using the study-reach topography captured by Structure-from-Motion (SfM) and various hydraulic data (depth, velocity, and water extent from aerial photographs). Vegetation inclusion in Delft3D was possible utilizing a function called ‘trachytopes’, which represented vegetation roughness and flow resistance and was calibrated utilizing data from a lupin-altered flow conveyance experiment. Morphologic calibration was achieved by simulating an observed near-mean annual flood event (209 m3 s-1) and adjusting the model parameters until the simulated morphologic changes best represented the observed morphologic changes captured by pre- and post-flood SfM digital elevation models. Calibration results showed that hydraulics were well represented, vegetation inclusion often improved the simulated water inundation extent accuracy at high flows, but that local erosion and sediment deposition were difficult to replicate. Simulation of morphological change was expected to be limited due to simplistic bank erosion prediction methods. Nevertheless, the model was considered adequate since simulated total bank erosion was comparable to that observed and realistic river characteristics (riffles, pools, and channel width) were produced.
Flood events ranging from the 2- to 500-year flood were simulated with the calibrated model, and lupin mortality was estimated using simulation results with the lupin mortality thresholds. Results showed that various degrees of lupin mortality occurred for the different flood events, but that the dominant mortality processes fluctuated between erosion, drag, and inundation. Sediment deposition-induced mortality was minimal, but was likely under-represented in the modeling due to poor model sediment deposition replication and possibly over-restrictive deposition mortality thresholds. The research presented in this thesis provided greater understanding of how natural flood events restore and preserve the floodplain habitats of the UWB and can be used to aid current and future braided river conservation and restoration efforts.