Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 164-178). Also available on the World Wide Web.

Universiẗat, Diss., 2000--Kiel.

Universiẗat, Diss., 2005--Jena.

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Many environmental free surface flows involve water and sediment transport. The net changes to the surface level of an erodible bed by sediment entrainment and deposition processes have a feedback effect on the local ow hydrodynamics. Bed morphological change is of great socio-economic and environmental importance in that it affects navigation, flood risk management, water quality, species diversity, and overall river sustainability. This thesis describes a mathematical model of the depth-averaged shallow water-sediment equations based on mass and momentum conservation laws. A 2D numerical model is then presented of the fully coupled, variable-density governing equations, which are solved using a Godunov-type HLLC scheme. Dependent variables are specially selected in the numerical model to handle the presence of the variable-density mixture in the mathematical formulation. The model includes suspended sediment, bedload transport, and bed morphological change. The numerical model is verified against benchmark analytical and semi-analytical solutions for complicated, clear water flows, bedload transport and suspended sediment transport. The well-balanced property of the governing equations is verified for a variable-density dam break flow over a bed step. Simulations of an idealised dam-break flow over an erodible bed, in excellent agreement with previously published results, validate the ability of the model to capture complex water-sediment interactions under rapidly-varying flow conditions and a mobile bed, and validate the eigenstructure of the system of variable-density governing equations. The model is then further validated against laboratory based data for complex 2D partial dam breaks over fixed and mobile beds, respectively. The simulations of 2D dam break flows over mobile beds highlight the sensitivity of the results to the choice of closure relationships for sediment transport. To investigate this further, a parameter study is carried out using a variety of commonly used empirical formulae for suspended sediment transport. The numerical model is also used to inform a theoretical model that predicts the flow through and around a porous obstruction in a shallow channel. This problem is relevant to several practical applications, including flow through aquatic vegetation and the performance of arrays of tidal turbines in a finite-width tidal channel. The theoretical model is used to reinterpret the core flow velocities in laboratory-based data for an array of emergent cylinders in a shallow channel. Comparison with experimental data indicates the maximum obstacle resistance for which the theoretical model is valid. In a final application, the theoretical model examines the optimum arrangement of tidal turbines to generate power in a tidal channel, confirming that natural bed resistance increases the power extraction potential for a partial tidal fence.

Seagrasses are marine foundation species that form ecologically important habitats in coastal areas around the world. They provide a range of ecosystem services, including coastal protection and the recently recognised large contribution to global carbon sequestration and storage. To date, the majority of published studies on the aforementioned ecosystem services is limited to specific geographic regions and seagrass species. This PhD study attempted to explore and provide the first evidence, to the best of our knowledge, on the role of Scottishseagrasses as carbon sinks and sediment stabilisers. In 2013, shoot dynamics of Zostera noltii plots were monitored biweekly and seasonally in the Forth estuary and digital images of the surveyed plots were taken for the development of a remote sensing technique which would accurately estimate the vegetation cover. In 2014, sediment samples from vegetated and unvegetated plots within beds of Z. marina and Z. noltii were collected from all the major estuaries along the east coast of Scotland, from the Firth of Forth in the south to Dornoch Firth in the north. Samples were analysed for organic matter, organic carbon, radionuclides 210Pb, 137Cs and 241Am, and δ13C in order to determine the organic matter and organic carbon density, longevity and sources of carbon respectively. To explore the role of seagrass in sediment deposition and stability, surface elevation was measured monthly in seagrass plots and bare sediment in the Forth estuary over two years. The results and main mechanisms underlying these findings are reported and discussed in detail in each chapter. In short, the proposed method based on digital images provided estimates of seagrass coverage that are more accurate than observers' estimates, with some constraints when macroalge and/or extreme light are present. Intertidal seagrass meadows in Scotland showed significantly enhanced carbon storage compared with bare sediment. Seagrass plots contained variable quantities of carbon in their sediments with species composition having a significant effect on carbon stocks, whereas depth and seagrass abundance had no effect on carbon stores. Despite their small above-ground biomass Scottish seagrass plots had a strong influence on sediment deposition and prevented erosion. Further research is needed to understand what factors drive large carbon sequestration and storage at some sites, thus contributing policy-relevant information on the prediction of the seagrass carbon hot-spots. Also, long-term datasets on surface elevation change are important in order to understand the effect of all the processes involved on sediment deposition in seagrass beds.

The stability and survival of salt marshes is typically linked to the competing influences of sea-level rise, subsidence, and sediment accumulation and erosion. However, consideration must also be made for wind waves that regulate the erosion of salt marsh shorelines and resuspend sediments in bordering tidal flats thus providing material for marsh accretion. This thesis examines the mechanisms in which wind waves affect marsh morphology, the mechanisms of salt marsh boundary erosion, in addition to linking the processes responsible for sediment mobilization between tidal flats and adjacent salt marshes. Sediment concentration within an open-coast marsh creek along the Louisiana chenier plain is shown to be related to the local wave climate and channel velocity. Calculations of sediment fluxes during ebb and flood tides indicates that while large volumes of sediment are mobilized into the marsh when wind waves are present, only a small portion is stored during each tidal cycle. In the coastal lagoon setting of Hog Island Bay, Virginia, marsh shoreline erosion rates were estimated from direct surveys and through analysis of aerial photographs. Erosion rates averaged 1.3 m/yr, similar to the 50-year historical average determined from previous work at the same location. Based on a calibrated numerical model for wind waves, the average erosion rate was linked to the energy of the waves attacking the marsh boundary. Additionally, results suggest that the effect of large waves forming during storms on erosion rates is negligible. Variations in erosion rates were linked to shoreline sinuosity (a proxy used to describe the result of wave concentration through erosive gullies), sediment characteristics, faunal activity, and marsh elevation. The culmination of the work leads to the hypothesis that waves have two opposite effects on salt marshes. On one hand they erode marsh boundaries thus reducing marsh area; on the other hand they mobilize large volumes of sediments in nearby tidal flats which may facilitate marsh accretion thus contrasting sea-level rise. In conclusion, wind waves destabilize marshes along the horizontal direction despite their potential vertical stability.

Submitted by GRENDA HINGRID ALCANTARA (grendaalcantara@outlook.com) on 2018-10-04T10:38:02Z No. of bitstreams: 1 Dissertação Grenda.pdf: 1551203 bytes, checksum: b29f515793930c19d42450e6fb2bd2c6 (MD5) / Rejected by Neli Silvia Pereira null (nelisps@fcav.unesp.br), reason: Solicitamos que realize correções na submissão seguindo as orientações abaixo: 1 - A ficha catalográfica e o certificado de aprovação estão em ordem invertida. Primeiro vem a ficha e depois o certificado. 2- Está faltando o resumo em inglês no repositório. Agradecemos a compreensão. on 2018-10-04T14:53:32Z (GMT) / Submitted by GRENDA HINGRID ALCANTARA (grendaalcantara@outlook.com) on 2018-10-04T22:12:52Z No. of bitstreams: 1 Dissertação Grenda imprimir .pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5) / Approved for entry into archive by Neli Silvia Pereira null (nelisps@fcav.unesp.br) on 2018-10-08T17:15:49Z (GMT) No. of bitstreams: 1 alcantara_gh_me_jabo.pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5) / Made available in DSpace on 2018-10-08T17:15:49Z (GMT). No. of bitstreams: 1 alcantara_gh_me_jabo.pdf: 1550980 bytes, checksum: 54ea8cf2c739e50badf9194898503dba (MD5) Previous issue date: 2018-07-11 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Em modelos de predição da erosão, caso do Water Erosion Prediction Project – WEPP, há a necessidade da determinação de propriedades do solo relativas à sua resistência à erosão. Deste modo, o objetivo deste trabalho foi determinar a erodibilidade em sulcos (Kr) e a tensão cisalhante crítica (tc) em Latossolos com diferentes teores de óxidos de ferro na região nordeste do Estado de São Paulo. A erosão em sulcos foi avaliada com chuva simulada de intensidade média de 65 mm h-1 aplicada por 65 minutos, além de fluxos adicionais de água (11, 39 e 64 L min-1), em seis sulcos pré-formados, em cada Latossolo, com 9,0 m de comprimento, 0,10 m de profundidade e 0,25 m de largura em cada solo. Os valores Kr para os Latossolos foram de 0,0094 s m-1 a 0,0035 s m-1. Os Latossolos mais cauliníticos apresentaram os maiores valores de Kr. Já os valores de tc foram de 2,915 N m-2 a 2,514 N m-2. A razão Ct/(Ct+Gb) explicou 90% das variações na erodibilidade em sulcos e 94% das observadas para a tensão cisalhante crítica nos quatro Latossolos. / In erosion prediction models, in the case of the Water Erosion Prediction Project (WEPP), it is necessary to determine the soil properties related to its erosion resistance. Thus, the objective of this work was to determine the RILL erodibility (Kr) and critical shear stress (tc) in Oxisols with different levels of iron oxides in the northeastern region of the State of São Paulo. Furrow erosion was evaluated with simulated rain of 65 mm h-1 mean intensity applied for 65 minutes, as well as additional water flows (11, 39 and 64 L min-1) in six preformed grooves in each Latosol, 9.0 m in length, 0.10 m in depth and 0.25 m in width in each soil. The Kr values for the Oxisols were 0.0094 s m-1 to 0.0035 s m-1. The most kaolinitic Oxisols presented the highest values of Kr. The values of tc were 2.915 N m-2 to 2.514 N m-2. The Ct/(Ct + Gb) ratio explained 90% of the variations in erodibility in grooves and 94% of those observed for critical shear stress in the four Oxisols. / CNPQ 143683/2016-0

Unconventional technology called "wet method" is a gentle pumping and removal of undesirable sediments not only in ponds and streams, but also in shallow waters, canals, harbors, lakes, recreational water areas and other tanks, decorated in treatment technology and water purification. This is a floating suction dredger WATERMASTER CLASSIC III, which functions as a classic and dragline as one and due to various peripheral devices isvaried uses. This machine is also ideal for repairing the damage during floods because of its versatility.