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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Rip current spacing in relation to wave energetics and directional spreading

Holt, Robert D. 06 1900 (has links)
Approved for public release, distribution is unlimited / Rip current spacings are compared with wave energetics and directional spreading in the Southern Monterey Bay. Southern Monterey Bay affords a unique environment to study rip currents owing to their prevalence created by near-normally incident waves on a sandy shoreline. It is hypothesized that rip current spacing is a function of wave directional spreading and energy flux, based on the morphodynamic modeling by Reniers et al. 2003. A gradient of wave energy flux exists due to headlands and refraction over Monterey Canyon. Rip currents are shown to occur between cusps in the shoreline, allowing cusp spacing to be a surrogate for rip spacing. Rip current spacing was inferred from beach morphology surveys, LIDAR imagery, and Argus cameras, and found to be O(150m) at Sand City and O(300m) at Marina, separated by 6km . Measured waves during a two month period using wave-rider buoys, show a gradient of across-shore energy flux between Sand City, 2 28000( / ) F Jm x . , and Marina, 2 33000( / ) F Jm x . . The two sites have the same peak directional spreading of energy value, 14 peak ̤= o , and slightly different bulk values for Sand City, 18 bulk ̤= o , and Marina, 20 bulk ̤= o . Therefore, the variations in rip current spacing could not be attributed to directional spreading but appear related to variations in energy flux. / Ensign, United States Naval Reserve
2

Dinâmica de cúspides praiais e fatores condicionantes: Massaguaçú, SP / Beach cusps dynamics and conditionig factors: Massaguaçú, SP

Santos, Hélio Teruo Hashizume dos 17 September 2015 (has links)
O presente trabalho tem por objetivo relacionar a ação das ondas incidentes no arco praial de Massaguaçú com a presença e o comportamento de feições morfológicas como as cúspides praiais. O conjunto de dados utilizados consiste em uma série de imagens provenientes do sistema Argus. Esse sistema utiliza cinco câmeras de alta resolução resultando em uma cobertura de 180° da zona costeira. A partir destas imagens realizou-se a digitalização das cúspides praiais encontrando-se duas linhas de cúspides, uma na face praial superior (CFS) e a outra na face praial inferior (CFI). Em conjunto com os dados de imagem foi analisado o clima de ondas atuantes durante o período. A presença de feições rítmicas foi alta no arco praial de Massaguaçú, sendo praticamente predominante na face praial superior. O espaçamento médio da CFS foi superior ao espaçamento da CFI e a alternância das condições atuantes foi determinante na redução do espaçamento assim como condições energéticas baixas. O aumento do espaçamento das cúspides ocorreu sob condições energéticas médias à altas e sob condições extremas observou tanto a destruição como o aumento das feições rítmicas. A interação entre o espraiamento e a morfologia existente, modulado pela variação do nível d\'água, foi um dos motores para a formação de cúspides em níveis inferiores enquanto que as condições extremas causaram sua destruição. / This study aims to relate the action of incident waves on Massaguaçú\'s beach with the presence and the behavior of morphological features such as beach cusps. The set of data used consists in a series of images from the Argus system. This system uses five high-resolution cameras resulting in a 180 ° coverage of the coastal zone. From these images, realize the presence of beach cusps lying in two rows on the beach face, one in the upper beach face (CFS) and the other in the lower beach face (CFI). At the same time with the image data the wave regime acting at Massaguaçú\'s beach was analyzed during the period. The presence of rhythmic features was almost constant Massaguaçú\'s beach face, nearly predominant on the upper beach face. The average spacing of CFS was greater than the spacing of the CFI and the interchange in active conditions was crucial in reducing the spacing as well as low energy conditions. The increased spacing of the cusps occurred under medium to high energy conditions and under extreme conditions both as increased and destruction of the rhythmic features were observed. The interaction between the swash motions and the existing morphology, modulated by varying the water level, was important for the formation of cusps at lower levels while the extreme conditions caused its destruction.
3

Dinâmica de cúspides praiais e fatores condicionantes: Massaguaçú, SP / Beach cusps dynamics and conditionig factors: Massaguaçú, SP

Hélio Teruo Hashizume dos Santos 17 September 2015 (has links)
O presente trabalho tem por objetivo relacionar a ação das ondas incidentes no arco praial de Massaguaçú com a presença e o comportamento de feições morfológicas como as cúspides praiais. O conjunto de dados utilizados consiste em uma série de imagens provenientes do sistema Argus. Esse sistema utiliza cinco câmeras de alta resolução resultando em uma cobertura de 180° da zona costeira. A partir destas imagens realizou-se a digitalização das cúspides praiais encontrando-se duas linhas de cúspides, uma na face praial superior (CFS) e a outra na face praial inferior (CFI). Em conjunto com os dados de imagem foi analisado o clima de ondas atuantes durante o período. A presença de feições rítmicas foi alta no arco praial de Massaguaçú, sendo praticamente predominante na face praial superior. O espaçamento médio da CFS foi superior ao espaçamento da CFI e a alternância das condições atuantes foi determinante na redução do espaçamento assim como condições energéticas baixas. O aumento do espaçamento das cúspides ocorreu sob condições energéticas médias à altas e sob condições extremas observou tanto a destruição como o aumento das feições rítmicas. A interação entre o espraiamento e a morfologia existente, modulado pela variação do nível d\'água, foi um dos motores para a formação de cúspides em níveis inferiores enquanto que as condições extremas causaram sua destruição. / This study aims to relate the action of incident waves on Massaguaçú\'s beach with the presence and the behavior of morphological features such as beach cusps. The set of data used consists in a series of images from the Argus system. This system uses five high-resolution cameras resulting in a 180 ° coverage of the coastal zone. From these images, realize the presence of beach cusps lying in two rows on the beach face, one in the upper beach face (CFS) and the other in the lower beach face (CFI). At the same time with the image data the wave regime acting at Massaguaçú\'s beach was analyzed during the period. The presence of rhythmic features was almost constant Massaguaçú\'s beach face, nearly predominant on the upper beach face. The average spacing of CFS was greater than the spacing of the CFI and the interchange in active conditions was crucial in reducing the spacing as well as low energy conditions. The increased spacing of the cusps occurred under medium to high energy conditions and under extreme conditions both as increased and destruction of the rhythmic features were observed. The interaction between the swash motions and the existing morphology, modulated by varying the water level, was important for the formation of cusps at lower levels while the extreme conditions caused its destruction.
4

Reinforcement of edge waves by beach cusps

Schönfeldt, Hans-Jürgen 27 September 2017 (has links)
Beach cusps, formed during a storm are observed. The storm acted for three hours together with high water conditions. These beach cusps exhibited a quasiuniform wavelength of 8 m. The measured topography after the storm, the calculated drift velocity of the incident wave and the synchronous edge wave are similar in scale and shape. The over one wavelength measured grain size is also correlated to the topography. A nonlinear hydro-numerical model is used to investigate the reaction of edge waves on alongshore change in bottom topography. Edge waves are greatly amplified over beach cusps. The relative amplification of edge waves on beach cusps is more than 17 times that without a change in longshore topography. Amplification is slightly greater for edge waves travelling in the same direction as the longshore current during the storm. An almost random positioning of sediment starts a feedback loop, which allows edge waves to grow and build short periodic cusps.
5

Alternative Statistical Methods for Analyzing Geological Phenomena: Bridging the Gap Between Scientific Disciplines

Van Gaalen, Joseph Frank 01 January 2011 (has links)
When we consider the nature of the scientific community in conjunction with a sense of typical economic circumstances we find that there are two distinct paths for development. One path involves hypothesis testing and evolution of strategies that are linked with iterations in equipment advances. A second, more complicated scenario, can involve external influences whether economic, political, or otherwise, such as the government closure of NASA's space program in 2011 which will no doubt influence research in associated fields. The following chapters are an account of examples of two statistical techniques and the importance of both on the two relatively unrelated geological fields of coastal geomorphology and ground water hydrology. The first technique applies a multi-dimensional approach to defining groundwater water table response based on precipitation in areas where it can reasonably be assumed to be the only recharge. The second technique applies a high resolution multi-scalar approach to a geologic setting most often restricted to either high resolution locally, or low resolution regionally. This technique uses time-frequency analysis to characterize cuspate patterns in LIDAR data are introduced using examples from the Atlantic coast of Florida, United States. These techniques permit the efficient study of beachface landforms over many kilometers of coastline at multiple spatial scales. From a LIDAR image, a beach-parallel spatial series is generated. Here, this series is the shore-normal position of a specific elevation (contour line). Well-established time-frequency analysis techniques, wavelet transforms, and S-Transforms, are then applied to the spatial series. These methods yield results compatible with traditional methods and show that it is useful for capturing transitions in cuspate shapes. To apply this new method, a land-based LIDAR study allowing for rapid high-resolution surveying is conducted on Melbourne Beach, Florida and Tairua Beach, New Zealand. Comparisons and testing of two different terrestrial scanning stations are evaluated during the course of the field investigation. Significant cusp activity is observed at Melbourne Beach. Morphological observations and sediment analysis are used to study beach cusp morphodynamics at the site. Surveys at Melbourne were run ~500 m alongshore and sediment samples were collected intertidally over a five-day period. Beach cusp location within larger scale beach morphology is shown to directly influence cusp growth as either predominantly erosional or accretional. Sediment characteristics within the beach cusp morphology are reported coincident with cusp evolution. Variations in pthesis size distribution kurtosis are exhibited as the cusps evolve; however, no significant correlation is seen between grain size and position between horn and embayment. During the end of the study, a storm resulted in beach cusp destruction and increased sediment sorting. In the former technique using multi-dimensional studies, a test of a new method for improving forecasting of surficial aquifer system water level changes with rainfall is conducted. The results provide a more rigorous analysis of common predictive techniques and compare them with the results of the tested model. These results show that linear interpretations of response-to-rainfall data require a clarification of how large events distort prediction and how the binning of data can change the interpretation. Analyses show that the binning ground water recharge data as is typically done in daily format may be useful for quick interpretation but only describes how fast the system responds to an event, not the frequency of return of such a response. Without a secure grasp on the nonlinear nature of water table and rainfall data alike, any binning or isolation of specific data carries the potential for aliasing that must be accounted for in an interpretation. The new model is proven capable of supplanting any current linear regression analysis as a more accurate means of prediction through the application of a multivariate technique. Furthermore, results show that in the Florida surficial aquifer system response-to-rainfall ratios exhibit a maxima most often linked with modal stage.

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