The ocean and acoustic modeling community has specifically asked for roughness from bathymetry. An effort has been undertaken to provide what can be thought of as the high frequency content of bathymetry. By contrast, the low frequency content of bathymetry is the set of contours. The two-dimensional amplitude spectrum calculated with the nonequispaced fast Fourier transform (Kunis, 2006) is exploited as the statistic to provide several parameters of roughness following the method of Fox (1996). When an area is uniformly rough, it is termed isotropically rough. When an area exhibits lineation effects (like in a trough or a ridge line in the bathymetry), the term anisotropically rough is used. A predominant spatial azimuth of lineation summarizes anisotropic roughness. The power law model fit produces a roll-off parameter that also provides insight into the roughness of the area. These four parameters give rise to several derived parameters. Algorithmic accomplishments include reviving Fox’s method (1985, 1996) and improving the method with the possibly geophysically more appropriate nonequispaced fast Fourier transform. A new composite parameter, simply the overall integral length of the nonlinear parameterizing function, is used to make within-dataset comparisons. A synthetic dataset and six multibeam datasets covering practically all depth regimes have been analyzed with the tools that have been developed. Data specific contributions include possibly discovering an aspect ratio isotropic cutoff level (less than 1.2), showing a range of spectral fall-off values between about -0.5 for a sandy- bottomed Gulf of Mexico area, to about -1.8 for a coral reef area just outside of the Saipan harbor. We also rank the targeted type of dataset, the best resolution gridded datasets, from smoothest to roughest using a factor based on the kernel dimensions, a percentage from the windowing operation, all multiplied by the overall integration length.

Visando garantir a disponibilidade hídrica em seus diferentes usos são construídos reservatórios, estes sempre associados a problemas de perda de volume de armazenamento devido ao processo de assoreamento. A atualização destes dados, bem como a quantificação do assoreamento geralmente é feita através de Levantamento Batimétrico. Apesar da grande importância do tema não é observado na literatura um método padronizado para a realização de estudos batimétricos, autores e organizações apresentam métodos dispares quanto à quantidade e disposição dos dados. Deste modo, a presente pesquisa buscou elencar os métodos apresentados na literatura e analisá-los quanto a precisão obtida no cálculo de volume do reservatório, utilizando como estudo de caso o reservatório da UHE Três Irmãos (SP). Observou-se que os MDTs gerados pelos métodos não representavam com fidelidade trechos estreitos do reservatório (braços) bem como o talvegue. Foi então proposto um método para a determinação do espaçamento entre seções bem como uma rotina para geração de MDT considerando características do talvegue. O método proposto para determinação do espaçamento entre seções se mostrou capaz de representar com relativa boa precisão trechos dos braços (diferença máxima encontrada de 5,01%) e apresentou tempo de coleta de dados de 60% do método mais preciso apresentado na literatura. A rotina de geração de MDT proporcionou em média melhora de aproximadamente 30% na qualidade dos dados de volume calculados. Por meio da aplicação dos métodos desenvolvidos na UHE Chavantes foi calculado um assoreamento de 3,91%, de acordo com os resultados, sem a utilização das rotina de geração de MDT desenvolvida cálculo do volume do reservatório seria subestimado em 1,61%, superestimando o cálculo do assoreamento. / Water reservoirs are built with the main purpose of guaranteeing water supply, however, their volume always decreases due the sedimentation processes. Bathymetric surveys can be deployed to assess the current volumetric capacity of a given reservoir and to estimate and quantify the sedimentation process. Although Bathymetric surveys are considered to be a key factor when analyzing and assessing properties of a given reservoir, a standard method for its deployment is yet to be defined. Authors and research groups presents different methods about the sampling rate as well as the choice of adequate spots for data collection. The overall goal of this research was to identify and analyze the different methods deployed in previous published literature analyzing the accuracy of the volume data provided by these different methods. Três Irmãos reservoir (São Paulo) was used as a case study where methods were compared. It was pointed out that the DEMs obtained were unable to accurately represent narrower reservoirs areas (tributaries) and the thalweg. Therefore was proposed a new method for determining the distance among survey sections as well as a routine for DEM generation takes into account the thalweg characteristics. Results revealed that the data pulled out was able to represent with accuracy the tributary areas (maximum difference was 5.01%). In addition, a reduced data collection time was observed (60%) when compared against the most accurate method found in published literature. The proposed technique for DEM generation indicated approximately 30% of quality improvement in the data calculated for the reservoir volume. The developed method was applied on a bathymetric survey conducted on the Chavantes reservoir (São Paulo). The loss of reservoir capacity assessed was 3.19%. According to results, a bathymetric survey which does not deploy the new method proposed would underestimate the reservoir\'s volume by 1.61% and overestimate the sedimentation process.

In April 2008, the non-profit organization Living Lands & Waters (LL&W) approached IIHR-Hydroscience and Engineering to assist with the preliminary scoping and assessment for the proposed dredging and restoration of the backwater region located near the confluence of the Iowa and Mississippi Rivers, commonly referred to as Boston Bay. IIHR was responsible for the measurement and analysis of relevant physical and chemical parameters including particle-size analysis of sediment cores; real-time monitoring of nitrate-nitrogen concentration of agricultural runoff entering Boston Bay; bathymetric surveying; as well as the development of a two-dimensional hydrodynamic capable of simulating the proposed dredging activity. Particle-size analysis was achieved using the hydrometer method of sedimentation to determine the distribution of fine particles (silt and clay) while traditional sieving techniques were employed to establish the proportions of sand-sized particles. Results indicate that the sediment contained in Boston Bay consists primarily of particles with diameters in the range of 2-50 µm, what the USDA considers silt, and clay. A real-time nitrate-nitrogen sensor was deployed at the Bay Island Drainage & Levee District pump intake from October 2008, through June 2009. The data collected, coupled with the daily maintenance logs from the pumping station, allow one to estimate that roughly 800 tons of nitrate-nitrogen were pumped into Boston Bay from the drainage district during the time period that the nitrate sensor was deployed in the field. Bathymetric surveying took place in March, 2009. Survey results indicate that the average elevation of Boston Bay is 531.9 feet above sea level (MSL, 1912). Overall, the bay is very flat with little topographic relief except in the areas of Bell's Pocket and the pond where the drainage district pumps discharge. These areas are much deeper than other areas of the bay, with elevations as low as 508 feet above sea level in the deepest regions. A two-dimensional hydrodynamic model of the bay (pre- and post-dredge) was constructed using the US Bureau of Reclamation's SRH-W modeling package. Initial results indicate that dredging Boston Bay does not appear to have detrimental impacts on the existing hydrology of the study area. Model outputs reveal that dredging will create greater availability of deep-water regions, with increased areas of faster moving current. The total area of inundation will also be affected by dredging, perhaps creating ideal habitat for hardwood tree species in portions of the study area that would otherwise be wet under existing conditions. Further studies should be conducted to couple the data obtained during particle-size analysis, with the model results to help estimate the feasibility of the proposed dredging activity and lifetime of the excavated channels.

The ability to detect buried mines on the seafloor remains one of the most important tasks in mine countermeasures. As such, there is a vested interest in the development of predictive models of mine burial. This research was conducted in support of the Office of Naval Research Program in Mine Burial Prediction. Repeat high-resolution multibeam bathymetry data were collected over the Indian Rocks Beach (IRB) mine burial experiment site during January through March of 2003, in order to observe in situ scour and burial of instrumented inert mines and mine-like cylinders. These data were also used to test the validity of the VIMS 2D mine burial model. A set of six high-resolution multibeam surveys were collected over the IRB experiment site. Three study sites within the IRB site were chosen: two fine sand sites, a shallow one located in ~ 13 meters of water depth and a deep site located in ~ 14 meters of water depth; and a coarse sand site in ~ 13 meters. Results from these surveys indicate that mines deployed in fine sand are upwards of 74.5% buried within two months of deployment. Mines deployed in the coarse sand showed a lesser amount of scour, burying until they presented roughly the same hydrodynamic roughness of the surrounding rippled bedforms. In general, scour around the mines formed pits ~ 0.30 meters deep, with the most pronounced scour occurring at the ends of the mine. The multibeam data were also used to test the VIMS 2D mine burial model, which estimates percent burial of cylindrical mines based on predictions of wave-induced scour. The model proved valid for use in areas of fine sand, sufficiently predicting burial over the course of the experiment. In the area of coarse sand, the model greatly overpredicted the amount of burial. This is believed to be due to the presence of ripples around the mines, which affect local bottom morphodynamics and are not accounted for in the model. This issue is currently being addressed by modelers.

Conventional bathymetric surveying is a costly and time consuming business. Even today many areas of shallow inshore ocean, some which encompass potential oil and gas fields, are only minimally charted. There is a need for reconnaissance systems which can effectively direct more expensive detailed surveys to best effect. Remote spectral bathymetry is one such system.A review of candidate sensor systems and processing algorithms highlighted problems due to changing bottom cover types and water quality parameters. A method, proposed and theoretically validated by other workers, was chosen for further investigation. This method develops an approximate relationship between the spectral content of the satellite data and water depths and then, by an iterative phase in the spatial domain, seeks to minimise the effect of spatially dependant variations.A study site in Cockburn Sound, Western Australia was chosen for a demonstration of this method. Spectral data are from the Landsat Thematic Mapper instrument and depth data are taken from Admiralty Charts. A variation on the originally proposed algorithm introduces spatial preprocessing phase, in which the image is segmented into zones where spectral relationships are expected to be more uniform. Two different methods of spatial mapping are used.The results demonstrate the capability of spatial modelling to improve remotely sensed depth estimates in the depth range of 5 to 12 m. The need for further research to better understand the shallow water spectral relationships is identified.

Analysis of the satellite altimetry based predicted bathymetry, magnetic anomalies, and earthquake seismic data relating to the geophysical structure on the Nazca plate indicates that the Galapagos Rise system served as the transitional spreading system between Pacific-Farallon spreading and the current East Pacific Rise (EPR) system. First order age/depth relationships for this area indicate that the Galapagos Rise, the most prominent extinct spreading system within the Nazca plate, accommodated most of the Pacific-Nazca plate separation from ~23 million years ago (Ma) to ~8 Ma. After this time, spreading was dominantly along the EPR, with probable ultra slow spreading along the Galapagos Rise continuing until very recent times (0-5 Ma). Magnetic lineations and depth trends across the Bauer Basin suggest that it was captured between the failing Galapagos Rise and the currently active EPR. Anomalously shallow ridge crests along the Galapagos Rise indicate that magmatic activity may have occurred until very recent time (0-5 Ma). Tightly curved (concave southward) fracture zones offsetting Galapagos Rise ridge segments indicate a pole of rotation at the present day position of ~22.5 S and ~99.5 W. The curvature of the fracture zones and the fan-shaped spreading pattern of seafloor structures produced at the Galapagos Rise indicate that the Galapagos Rise initiated parallel to the Mendaña fracture zone. Consistent with the rotation of the Nazca plate after the fragmentation of the Farallon plate, the Galapagos Rise rotated counterclockwise during its active phase. The Galapagos Rise initiated in the vicinity of Gallego fracture zones and propagated southward. Failure of the Galapagos Rise occurred as spreading jumped westward in stages to the East Pacific Rise.

Swath bathymetry sidescan (SBS) sonar and the angle-of-arrival processing that underlies these systems has the capability to produce much higher resolution three dimensional imagery and bathymetry than traditional beamformed approaches. However, the performance of these high resolution systems is limited by signal-to-noise ratio (SNR) and they are also susceptible to multipath interference. This thesis explores two methods for increasing SNR and mitigating multipath interference for SBS systems. The first, binary coded pulse transmission and pulse compression is shown to increase the SNR and in turn provide reduced angle variance in SBS systems. The second, transmit beamforming, and more specifically steering and shading, is shown to increase both acoustic power in the water and directivity of the transmitted acoustic radiation. The transmit beamforming benefits are achieved by making use of the 8-element linear angle-of-arrival array typical in SBS sonars, but previously not utilized for transmit. Both simulations and real world SBS experiments are devised and conducted and it is shown that in practice pulse compression increases the SNR, and that transmit beamforming increases backscatter intensity and reduces the intensity of interfering multipaths. The improvement in achievable SNR and the reduction in multipath interference provided by the contributions in this thesis further strengthens the importance of SBS systems and angle-of-arrival based processing, as an alternative to beamforming, in underwater three dimensional imaging and mapping. / Graduate / 2015-04-15 / 0544 / 0547 / mark.butowski@gmail.com

Made available in DSpace on 2015-03-26T13:28:24Z (GMT). No. of bitstreams: 1 texto completo.pdf: 6794680 bytes, checksum: 55db799523fa29d2ac3a1dcd7961c68e (MD5) Previous issue date: 2013-08-27 / Dams are part of the history of civilizations, being among the first works architected by humanity. Reservoirs, formed by dams, act as sediment retention basins, promoting its gradual sedimentation. The accumulation of sediments on reservoir s bottom modifies the morphology of the relief, which should be periodically reviewed by the update of the elevation x area x volume curve (EAV), based on bathymetric surveys. This study aimed to evaluate the process of sedimentation on the Pipoca hydroelectric power plant reservoir, by performing bathymetric surveys and the characterization of the reservoir bottom sediments. Two bathymetric surveys were executed, the first, in 2012, with a single beam echosounder and the second, in 2013, with a multibeam echosounder. In addition to the comparison between the two methodologies used in the echosounders, it was analyzed the results obtained before and after the filling of the reservoir, by the generation of Digital Elevation Models (DEMs). The DEM before reservoir s filling was obtained from contour s lines of the region and some bathymetric sections of the river. These DEM enabled the generation of EAV curves before and after reservoir s filling, enabling the identification of deposited sediment volumes during the current operation period of the hydroelectric power plant. In the first bathymetric survey it was obtained a deposited sediment volume of 0.404 hm3, which represents an average annual sedimentation of 0.80%. In the second bathymetric survey was obtained a deposited sediment volume of 0.369 hm3, which represents an average annual sedimentation of 0.63%. The difference on the volumes obtained by the two equipments can be explained by the greater accuracy provided by the multibeam echo sounder. This multibeam echo sounder technology is able to provide 100% coverage of the area and requires less interpolation on the collected data than the other technology. / As barragens fazem parte da história das civilizações, estando entre as primeiras obras arquitetadas pela humanidade. Os reservatórios, formados pela construção de barragens, atuam como verdadeiras bacias de retenção de sedimentos, promovendo o seu assoreamento gradual. O acúmulo de sedimentos do fundo do reservatório modifica a morfologia do relevo, que deve ser reavaliada periodicamente a partir da atualização das curvas cota x área x volume (CAV), com base em levantamentos batimétricos. O presente estudo visou avaliar o processo de assoreamento no reservatório da PCH Pipoca (MG), por meio da realização de levantamentos batimétricos e pela caracterização dos sedimentos de fundo do reservatório. Foram realizados dois levantamentos batimétricos, o primeiro, em 2012, com ecobatímetro monofeixe e o segundo, em 2013, com ecobatímetro multifeixe. Além da comparação entre as metodologias utilizadas no uso dos ecobatímetros, foram analisados os resultados obtidos antes e depois do enchimento do reservatório, a partir da geração de Modelos Digitais de Elevação (MDEs). O MDE antes do enchimento do reservatório, em 2006, foi obtido a partir de curvas de nível da região e de algumas seções batimétricas. Estes MDEs permitiram a geração das curvas CAV anterior e posterior ao enchimento do reservatório, possibilitando identificar volumes de sedimento depositado ao longo do período de operação do empreendimento. Na primeira batimetria do reservatório foi obtido um volume de sedimento depositado de 0,404 hm3, representando uma taxa média de assoreamento anual de 0,80%. Já na segunda batimetria do reservatório foi obtido um volume de sedimento depositado de 0,369 hm3, representando uma taxa média de assoreamento anual de 0,63%. Esta diferença pode ser justificada pelo fato de o ecobatímetro multifeixe proporcionar uma precisão maior no levantamento, ao ser capaz de mapear 100% da área, demandando pouca interpolação dos dados coletados.

Swath bathymetry sidescan (SBS) sonar and the angle-of-arrival processing that underlies these systems has the capability to produce much higher resolution three dimensional imagery and bathymetry than traditional beamformed approaches. However, the performance of these high resolution systems is limited by signal-to-noise ratio (SNR) and they are also susceptible to multipath interference. This thesis explores two methods for increasing SNR and mitigating multipath interference for SBS systems. The first, binary coded pulse transmission and pulse compression is shown to increase the SNR and in turn provide reduced angle variance in SBS systems. The second, transmit beamforming, and more specifically steering and shading, is shown to increase both acoustic power in the water and directivity of the transmitted acoustic radiation. The transmit beamforming benefits are achieved by making use of the 8-element linear angle-of-arrival array typical in SBS sonars, but previously not utilized for transmit. Both simulations and real world SBS experiments are devised and conducted and it is shown that in practice pulse compression increases the SNR, and that transmit beamforming increases backscatter intensity and reduces the intensity of interfering multipaths. The improvement in achievable SNR and the reduction in multipath interference provided by the contributions in this thesis further strengthens the importance of SBS systems and angle-of-arrival based processing, as an alternative to beamforming, in underwater three dimensional imaging and mapping. / Graduate / 0544 / 0547 / mark.butowski@gmail.com

Visando garantir a disponibilidade hídrica em seus diferentes usos são construídos reservatórios, estes sempre associados a problemas de perda de volume de armazenamento devido ao processo de assoreamento. A atualização destes dados, bem como a quantificação do assoreamento geralmente é feita através de Levantamento Batimétrico. Apesar da grande importância do tema não é observado na literatura um método padronizado para a realização de estudos batimétricos, autores e organizações apresentam métodos dispares quanto à quantidade e disposição dos dados. Deste modo, a presente pesquisa buscou elencar os métodos apresentados na literatura e analisá-los quanto a precisão obtida no cálculo de volume do reservatório, utilizando como estudo de caso o reservatório da UHE Três Irmãos (SP). Observou-se que os MDTs gerados pelos métodos não representavam com fidelidade trechos estreitos do reservatório (braços) bem como o talvegue. Foi então proposto um método para a determinação do espaçamento entre seções bem como uma rotina para geração de MDT considerando características do talvegue. O método proposto para determinação do espaçamento entre seções se mostrou capaz de representar com relativa boa precisão trechos dos braços (diferença máxima encontrada de 5,01%) e apresentou tempo de coleta de dados de 60% do método mais preciso apresentado na literatura. A rotina de geração de MDT proporcionou em média melhora de aproximadamente 30% na qualidade dos dados de volume calculados. Por meio da aplicação dos métodos desenvolvidos na UHE Chavantes foi calculado um assoreamento de 3,91%, de acordo com os resultados, sem a utilização das rotina de geração de MDT desenvolvida cálculo do volume do reservatório seria subestimado em 1,61%, superestimando o cálculo do assoreamento. / Water reservoirs are built with the main purpose of guaranteeing water supply, however, their volume always decreases due the sedimentation processes. Bathymetric surveys can be deployed to assess the current volumetric capacity of a given reservoir and to estimate and quantify the sedimentation process. Although Bathymetric surveys are considered to be a key factor when analyzing and assessing properties of a given reservoir, a standard method for its deployment is yet to be defined. Authors and research groups presents different methods about the sampling rate as well as the choice of adequate spots for data collection. The overall goal of this research was to identify and analyze the different methods deployed in previous published literature analyzing the accuracy of the volume data provided by these different methods. Três Irmãos reservoir (São Paulo) was used as a case study where methods were compared. It was pointed out that the DEMs obtained were unable to accurately represent narrower reservoirs areas (tributaries) and the thalweg. Therefore was proposed a new method for determining the distance among survey sections as well as a routine for DEM generation takes into account the thalweg characteristics. Results revealed that the data pulled out was able to represent with accuracy the tributary areas (maximum difference was 5.01%). In addition, a reduced data collection time was observed (60%) when compared against the most accurate method found in published literature. The proposed technique for DEM generation indicated approximately 30% of quality improvement in the data calculated for the reservoir volume. The developed method was applied on a bathymetric survey conducted on the Chavantes reservoir (São Paulo). The loss of reservoir capacity assessed was 3.19%. According to results, a bathymetric survey which does not deploy the new method proposed would underestimate the reservoir\'s volume by 1.61% and overestimate the sedimentation process.