Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 76-87). Also available via the Internet.

In this thesis we aim to provide computationally efficient methods of performing waterbarrier simulations. The innate challenge in simulations of structures such as sea or surge barriers is resolution. Because barriers tend to be long and thin compared to the surrounding landscapes they protect, one must put mesh refinement on the barrier region in order to even numerically recognize the barrier’s presence. This is a costly computation due to the CFL condition which puts a strict limit on the size of time step proportional to the spatial mesh size. Another issue is the complexity of meshing near the barrier. Since barriers are most likely slanted or have certain shapes, the grid has to reflect this in the form of a grid mapping or an unstructured grid. To mitigate the issue of resolution, we propose an approximation of the barrier with a line interface embedded on a Cartesian grid, reducing our problem to an embedded boundary problem. Then to avoid complex meshing, we develop three cut cell methods on two shapes of barriers: 1) the h-box method (HB), 2) the state redistribution method (SRD), and 3) the cell merging method (CM). Doing this two-step approach means that we can lower the resolution near the barrier region and still feel the presence of the barrier and capture its effect, which would otherwise not be the case if we relied on resolution for representation of the barrier. This does not mean that we are losing accuracy by lowering resolution, however. Rather, we are maintaining about the same accuracy while also lowering resolution (and thus cutting computational cost), which we show by comparison with a refined barrier. We solve the shallow water equations as our underlying PDEs to simulate water interaction with the barrier, as they are commonly used in tsunami and storm simulations. We implement our work on the PYCLAW framework, which is an objected oriented program that solves conservation laws.

Recent research has indicated that submarine groundwater discharge (SGWD) occurs in the Chesapeake Bay, and that discharged groundwater can be contaminated with nutrients and toxic substances. Although discharge has been measured directly on a local level, a convenient method for determining the spatial distribution of SGWD on a large scale has not yet been devised. Although current watershed mass balance approaches have been used to estimate gross SGWD, this method cannot identify areas at high risk for contaminant input. A family of innovative computer mapping programs called Geographic Information Systems (GIS) have emerged from the software industry that serve not only as mapping tools but also as databases designed to manage spatial data) The GIS approach allows straightforward manipulation and presentation of data that is spatially related. In the research presented here, a GIS was applied to the problem of large-scale determination of SGWD and nutrient loads for the Eastern Shore of Virginia. Computerized data layers including land use, hydraulic gradient and soil permeability were used to create a GIS model of SGWD on Virginia's Eastern Shore. The model was used to predict spatial distribution of SGWD as well as the nutrient loading from nearshore agriculture and on-site waste treatment technologies. While sufficient field data for reliable calibration and verification of the model did not exist, the available data and the output of the GIS model were consistent. The methodology developed predicts that 90% of the impact from nearshore land use occurs in the southwestern quadrant of the Eastern Shore. In addition, the model determined locations where urban land use (septic tanks) may present a nutrient and coliform contamination danger. The model identified areas susceptible to contamination through discharge to a resolution of about 33 meters, showing that GIS can function as a local as well as regional management tool. The GIS framework is also expandable. The model can be modified to accommodate new data as research continues into the phenomenon of submarine groundwater discharge. This synthesis represents the first large-scale groundwater discharge analysis of the Eastern Shore and exists as part of an ongoing investigation to characterize groundwater-surface water interactions of the Eastern Shore. / Master of Science

Thesis (M.Sc.)--University of Adelaide, Dept. of Geology and Geophysics, 2003. / Includes bibliographical references (leaves 112-115).

Includes bibliographical references (leaves 112-115) Towed DC Resistivity and Transient Electromagnetic arrays have been trialled for suitability in monitoring salt-loads on the Murray River at Waikerie, South Australia.