No description available.

No description available.

One objective of this project is to set up a two-dimensional model for exploring the flushing process of trapped saltwater subject to upstream freshwater turbulent flow. The multiphase Eulerian model, a part of commercial code FLUENT6.2, has been applied for the first time to study this complex mixing interaction in estuary. The distinguishing characteristic of this model is to treat saltwater and freshwater as two single miscible phases instead of a mixture phase with density variation, and the advantage of using a multiphase approach over a single-phase model is that it can efficiently and accurately treat both the free water surface and relatively high density excess between two fluids simultaneously. The other objective of this project is to develop a three-dimensional model based on the FVCOM open source code, with the aim to better understand the estuarine hydrodynamics with or without the presence of typhoon. It is found that the original FVCOM code can not reproduce an accurate tidal hydrodynamics in estuary. An improved simulation of the bed friction has been incorporated into the existing code for estuarine tide. This model has also been developed by including air-pressure gradient term to study the hydrodynamic response to cyclonic typhoon. To include the effect of typhoon (wind stress and pressure deficit), a symmetrical cyclone model is adopted. However, the typhoon-induced wind field has been predicted poorly when the typhoon enters the near-shore region. This is because the typhoon quickly loses its symmetrical property in the near-shore region. To overcome this difficulty, an asymmetrical cyclone model is derived on the basis of characteristic isobar. The accuracy of open sea boundary for storm surge model has also been improved by using large scale model. Comparison results show a good agreement with numerical simulations and physical measurements.

Graduation date: 1976

In Galveston Bay, Texas, the eastern oyster, Crassostrea virginica, is found throughout the bay both intertidal along mudflats and subtidal where their self-built reefs extend vertically deeper. The eastern oyster is an important ecological and economical resource and as such has led to studies regarding their community structure to permit effective creation of artificially built reefs and restoration of existing ones. The presence of the oil and gas industry coupled with increased oyster mortality led to investigations to determine the effects of petroleum substances on the setting, growth, and mortality of the eastern oyster. Many of those studies indicated increased settlement and increased growth of oysters on substrate coated with oil. A field conducted experiment was used to assess the settlement of oyster larvae on cleaned oyster shells coated with two different types of petroleum substances (mineral oil and motor oil), comparing viscosities, in a shallow bayou in Galveston, Texas, where the eastern oyster dominates the intertidal zone. Oyster shells were used as cultch material and divided into three groups; a non-treated control group, mineral oil treated group, and a motor oil treated group. Nekton assemblages, distributions of the ivory barnacle, Balanus eberneus, and Dermo disease infection were assessed. Settlement of oyster larvae occurred in all three groups with no significant difference of preference; algae and sediment present on the shells coupled with the presence of predators most likely caused reduced numbers of spat settlement. Species richness was equal among the groups but varied in evenness of individual species.

Thesis (Ph. D.)--University of Rhode Island, 2003. / Typescript. Includes bibliographical references (leaves 179-210).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 207-235). Also available via the Internet.

Thesis (Ph. D.)--Duke University, 2008. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

This study aims to describe and quantify the important sedimentary processes which control the dispersal and accumulation of sediment in the Dwyryd Estuary, adjacent to Tremadog Bay in West Wales. It is shown that sedimentation in the estuary is dominantly control by fast tidal currents, and in the bay by weak tidal currents. Landward transport of coastal sediments by tidal currents is the residual sediment transport path. The spatial distribution of textural parameters of the estuarine sediments is related to the strength of tidal currents as well as the morphology and bathymetry of the study area. The estuarine sediments, predominantly sand, are very similar in texture and mineralogy to the adjacent beach sediments but markedly different to the river sediments. However, the beach sediments are slightly coarser and more poorly sorted than the estuarine sediments. In contrast, sediment in the deeper parts of Tremadog Bay are finer than both the estuarine and beach sediments due to the presence of substantial admixture of mud. The grain size distributions of most of the sediments are neither lognormal nor log-hyperbolic reflecting the great variability of hydrodynamic conditions in the study area. Using previously published flume data, a new sediment transport rate formula in the form of a power law has been developed for computation of total sediment load from the bed mean grain size and flow parameters: Uc The exponent n varies from 2.7 (for 0.93 mm sand) to 4.18 (for 0.19 mm sand). This is in contrast to the Bagnold (1966) formula which regards the exponent value (equal to 3) as constant for all grain sizes. Sediment transport patterns depend on the asymmetry between flood and ebb tidal currents due to distortion of the tidal wave on entering the estuary. Estimates of sediment budgets from surveyed profiles suggest that large amounts of sand have been transported from coastal areas into the estuary, supporting the mineralogical evidence. The estimates are of the same order of magnitude as estimates using flow velocity data and the above sediment transport formula.