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Full-Text Articles in Engineering
The Impact Of Drainage Ditches On Salt Marsh Flow Patterns, Sedimentation And Morphology: Rowley River, Massachusetts, Lynsey E. Lemay
The Impact Of Drainage Ditches On Salt Marsh Flow Patterns, Sedimentation And Morphology: Rowley River, Massachusetts, Lynsey E. Lemay
Dissertations, Theses, and Masters Projects
Salt marshes along many tidal systems in New England have been ditched since colonial times. These ditches have been thought to help control mosquito populations and increase salt marsh hay production by improving water drainage from the marsh. Although these ditches are prominent geomorphic features, little quantitative work has focused on how these man-made ditches may alter marsh hydrology and geomorphology. This study attempts to quantify the ways in which ditches alter sediment and water transport pathways and how that affects the overall morphology and surface geology. This study also addresses treatment affects on sedimentation from fertilization and fish removal …
Simulation Of Turbidity Maximums In The York River, Virginia, Jae-Il Kwon
Simulation Of Turbidity Maximums In The York River, Virginia, Jae-Il Kwon
Dissertations, Theses, and Masters Projects
Two of the most important processes in cohesive sediment transport, erosion rate and settling velocity, were the focus of this study. Settling velocities were estimated by the Owen tube method and the acoustic Doppler velocimeter (ADV) method. A novel erosion model, namely a constant erosion rate model, was implemented in a three-dimensional hydrodynamic eutrophication model (HEM-3D) to simulate the turbidity maximums in the York River system, Virginia. Two one-month periods of model simulations were conducted to mimic typical dry (November--December, 2001) and wet (March--April, 2002) seasons. In order to have enough data to verify the model, four slack water surveys …
Laboratory Oxide Coatings: Physical Form And Surface Chemistry, Kea U. Duckenfield
Laboratory Oxide Coatings: Physical Form And Surface Chemistry, Kea U. Duckenfield
Dissertations, Theses, and Masters Projects
The impact of dissolved trace metals on aquatic ecosystems and human health is controlled by sorption, i.e., binding to the surfaces of environmental particles. Since many environmental particles are coated with highly reactive substances, and since discrepancies in trace metal sorption behavior persist between oxides developed in the laboratory and environmental oxide phases, it was hypothesized that the physical form of oxide coatings may influence the chemical properties of the coated particle. Therefore, relationships between the physical forms of several different Fe(III) oxide coatings and the Cu(II) sorption behavior of the coated solids were investigated in comparison with the component …
Nitrate Reduction At The Groundwater - Salt Marsh Interface, Craig -1967 Tobias
Nitrate Reduction At The Groundwater - Salt Marsh Interface, Craig -1967 Tobias
Dissertations, Theses, and Masters Projects
The influence of groundwater discharge on the hydrology and biogeochemical cycling of nitrogen in a fringing intertidal wetland was studied by characterizing groundwater discharge, determining N-cycling rates in cores, and examining nitrate reduction in situ using 15N enrichment and natural gradient tracer techniques. Groundwater discharge was estimated by three independent methods: Darcy's Law, a water/salt mass balance, and a subsurface tracer test. Seasonal patterns of discharge predicted by Darcy's Law and the mass balance were similar. Discharge maxima and minima occurred in April and September, respectively. The water/salt mass balance provided the more reasonable estimate of groundwater flux at high …
Water Quality Modeling As An Inverse Problem, Jian Shen
Water Quality Modeling As An Inverse Problem, Jian Shen
Dissertations, Theses, and Masters Projects
An inverse mathematical estuarine eutrophication model has been developed. The model provides a framework to estimate unknown parameters by assimilation of the concentration data of those state variables. The inverse model developed is a laterally integrated, two-dimensional, real-time model which consists of a hydrodynamic model, an eutrophication model and an adjoint model. The hydrodynamic model provides the dynamic fields for both the eutrophication model and the adjoint model. The eutrophication model simulates eight water quality state variables which are phytoplankton, organic nitrogen, ammonium nitrogen, nitrite-nitrate nitrogen, organic phosphorus, inorganic (ortho) phosphorus, carbonaceous biochemical oxygen demand and dissolved oxygen. The adjoint …
Resuspension Behavior Of Natural Estuarine Sediments, Chang-Hee Lee
Resuspension Behavior Of Natural Estuarine Sediments, Chang-Hee Lee
Dissertations, Theses, and Masters Projects
The resuspension behavior of natural estuarine sediments was studied using the VIMS Sea Carousel, a benthic annular flume. The bed shear stresses produced by the flume were measured by a hot-film sensor mounted flush on the bottom of a laboratory version of the Carousel under a clear-water and flat-bottom condition. Measurements showed a reasonably uniform bed shear stress across the channel and agreed with the relationship &\tau\sb{lcub}\rm b{rcub}=0.011\Omega\sp{lcub}1.69{rcub},& where &\Omega& = ring speed (rpm) and &\tau\sb{lcub}\rm b{rcub}& = spatially-averaged bed shear stress (N/m&\sp2&), predicted from a previous numerical study. Thus, the &\tau\sb{lcub}\rm b{rcub}& was used as a bed shear stress …
Late Cenozoic Landforms, Stratigraphy And History Of Sea Level Oscillations Of Southeastern Virginia And Northeastern North Carolina, Pamela Crowson Peebles
Late Cenozoic Landforms, Stratigraphy And History Of Sea Level Oscillations Of Southeastern Virginia And Northeastern North Carolina, Pamela Crowson Peebles
Dissertations, Theses, and Masters Projects
A depositional model accounting for the stratigraphic sequences which accumulate during a marine transgression across a dissected coastal plain aids in understanding the geologic history of southeastern Virginia and northeastern North Carolina. Application of this model to the Shirley Formation (middle Pleistocene) and the Sedgefield and Lynnhaven members of the Tabb Formation (late Pleistocene) allows delineation of (1) the facies within, (2) the areal extent of, and (3) the landforms associated with these lithostratigraphic units. Facies within each lithostratigraphic unit consist of (1) a vertical succession from local, basal, channel-fill deposits and coarse, basal, lag deposits which grade upward into …
Forecasting Beach Erosion Along The Oceanic Coastlines Of The Northeast And Mid-Atlantic States, William S. Richardson
Forecasting Beach Erosion Along The Oceanic Coastlines Of The Northeast And Mid-Atlantic States, William S. Richardson
Dissertations, Theses, and Masters Projects
No abstract provided.