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Full-Text Articles in Engineering
Modeling Flocculation And Deflocculation Processes Of Cohesive Sediments, Xiaoteng Shen
Modeling Flocculation And Deflocculation Processes Of Cohesive Sediments, Xiaoteng Shen
Dissertations, Theses, and Masters Projects
The transport and fate of cohesive sediments are responsible for many engineering, environmental, economic and policy issues that relate to, for example, siltation and dredging in navigation channels, water quality, water turbidity, pollutant transports, and biological ecosystem responses. Our current understanding, however, is insufficient to conduct accurate quantitative predictions of these processes. This is because the cohesive particles in natural waters will flocculate, which determines the settling, and thus the deposition behaviors. The simulation of flocculation processes is a primary challenge since the time variation of Floc Size Distribution (FSD) is controlled by a partial differential equation that also contains …
Assessing The Impact Of Climate Change On Proposed Restoration Of The Lynnhaven River Ecosystem, Emily E. Skeehan
Assessing The Impact Of Climate Change On Proposed Restoration Of The Lynnhaven River Ecosystem, Emily E. Skeehan
Dissertations, Theses, and Masters Projects
Environmental degradation of the Chesapeake Bay (CB) and its sub-estuaries has been linked to population growth in the surrounding coastal zone, rapid development in the watershed and resultant nutrient loading into the Bay. Consequently, the federal government and its partners have developed restoration plans to mitigate the effects of eutrophication and improve essential ecosystem functions, though few restoration plans have considered the interactive effects of climate change. Climate change and other anthropogenic drivers are causing changes in ecosystem structure and function, thereby impacting the beneficial services ecosystems provide. While some studies have attempted to quantitatively predict the benefits of ecosystem …
Controls On Erodibility In A Partially Mixed Estuary, York River, Virginia, Patrick J. Dickhudt
Controls On Erodibility In A Partially Mixed Estuary, York River, Virginia, Patrick J. Dickhudt
Dissertations, Theses, and Masters Projects
A time-series of erodibility measurements and physical and biological sediment properties was used to evaluate spatial and temporal variability in cohesive bed erodibility and controls on erodibility in the York River estuary, VA. Two sites near Clay Bank displayed dramatic seasonal variations in bed erodibility while a third near Gloucester Point displayed a more consistent level of low erodibility. Total bed solids fraction and cohesive sediment grain size were not correlated with bed erodibility. The surficial sediments were characteristically composed of 2% to 50% sand supported in a mud matrix. The total solids fraction of the bed was shown to …
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 …
Evaluating Restored Oyster Reefs In Chesapeake Bay: How Habitat Structure Influences Ecological Function, Janet A. Nestlerode
Evaluating Restored Oyster Reefs In Chesapeake Bay: How Habitat Structure Influences Ecological Function, Janet A. Nestlerode
Dissertations, Theses, and Masters Projects
A shortage of shell resources for restoring reefs of the Eastern oyster, Crassostrea virginica, has led to widespread use of substitute materials. The effectiveness of such alternative substrates as habitat for reef-associated fauna other than oysters is largely unresolved. I investigated the habitat value of oyster shell, surf clam (Spisula solidissima) shell, and pelletized coal ash reefs for benthic and nektonic communities. Oyster recruitment, survival, and growth were monitored on reefs of oyster and surf clam shell near the mouth of Chesapeake Bay and York River, USA. Oyster shell supported greater oyster growth and survival and offered the highest degree …
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 …
Laboratory And Field Investigations To Determine The Chemical Factors Affecting Zinc And Iron Transport At An Industrial Waste Facility, Michael Lawrence Chasey
Laboratory And Field Investigations To Determine The Chemical Factors Affecting Zinc And Iron Transport At An Industrial Waste Facility, Michael Lawrence Chasey
Dissertations, Theses, and Masters Projects
No abstract provided.