Groundwater aquifers make up the primary source of drinking water in Florida. It is imperative to protect and maintain water quality to ensure optimal drinking water conditions. Florida is known for being prone to sinkholes due to karst features. One sinkhole event occurred beneath a phosphogypsum stack, and leaked a large amount of radioactive waste in the Floridan aquifer, raising water quality concerns. To study the behavior of contaminant transport, the radioactive waste plume was modeled by coupling hydraulic and chemistry concepts. Adsorption was studied to see if it can serve as a potential remediation solution to the contaminant waste, using available adsorption knowledge and data from previous studies. Results suggest that simulating mineral adsorption helped limit how far the waste stack would travel in the aquifer, however it would still pose risk in water quality, as drinking water wells are situated along the path of the contaminant plume. Implementation of treatment wells and monitoring would ensure drinking water criteria are met. Acknowledging that the Floridan aquifer contains karst features that consist of limestone fractures and the rock matrix, groundwater flow patterns may be influenced over time. For instance, fractures (or conduits) can conduct larger amounts of groundwater at higher conductivities, which could have implications on groundwater/contaminant transport. To model this process, a karst evolution model utilizing hydraulic and chemistry concepts are applied in a basin in Florida. Results indicate the karst model reproduces head profiles and estimates the age of several conduits. A sensitivity analysis was conducted to investigate how karst evolution is influenced by hydraulic and chemistry parameters. Results show that fracture length has more influence on karst evolution, however other physical parameters show some influence as well. A karst conduit network was simulated for the Silver Springs springshed, based on obtained potentiometric head data. Implementing information on aquifer chemistry and fracture geometry resulted in a unique realization of a karst network. During this process, flow rates change direction, inducing backflow, which can have implications on groundwater resources. Overall, an improved understanding of karst processes can aid in better characterizing conduit flow patterns and improve water resources management.

One of the major concerns in the behavior of an earth dam is the change in the exit gradient and the impact on the slope stability under drawdown conditions. Drawdown can cause increased seepage forces on the upstream slope which may result in the movement of soil particles in the flow direction and cause erosion problems. In this research, a numerical approach, based on the finite element method (FEM) is used to analyze the seepage through the dam and its foundation to study exit gradients and slope stability under both steady-state and transient conditions. The results show that a central core is important in reducing the flux through the dam. Constructing a cutoff under the core further increases the efficiency of the core and lowers the phreatic line. However, it is seen that the submerged weight increases when the earth dam with a core or with a complete cutoff which causes higher water flux to flow out of the dam under the drawdown condition. The exit gradient at the upstream slope may reach critical levels and cause failure of the dam due to erosion. Adding an upstream filter is studied as a possible solution to this problem. Two configurations of the filters are modeled and the slope filter configuration performed best in reducing the exit gradient at the upstream face. A low permeability core with a cutoff increases deformation of the soil because of increased saturated areas in the upstream region. The factor of safety of the slope is also reduced because of the increased buoyancy of the soil at the upstream side of the dam. The soil properties of the upstream filter have a significant influence on the slope stability against sliding. An upstream slope filter increases the stability of the slope while a central filter decreases it.

Salt marshes are valued for providing protective and non-protective ecosystem services. Accurate digital elevation models (DEMs) in salt marshes are crucial for modeling storm surges and determining the initial DEM elevations for modelling marsh evolution. Due to high biomass density, lidar DEMs in coastal wetlands are seldom reliable. In an aim to reduce lidar-derived DEM error, several multilinear regression and random forest models were developed and tested to estimate biomass density in the salt marshes near Saint Marks Lighthouse in Crawfordville, Florida. Between summer of 2017 and spring of 2018, two field trips were conducted to acquire true elevation and biomass density measures. Lidar point cloud data were combined with vegetation monitoring imagery acquired from Sentinel-2 and Landsat Thematic Mapper (LTM) satellites, and 64 field biomass density samples were used as target variables for developing the models. Biomass density classes were assigned to each biomass sample using a quartile approach. Moreover, 346 in-situ elevation measures were used to calculate the lidar DEM errors. The best model was then used to estimate biomass densities at all 346 locations. Finally, an adjusted DEM was produced by deducting the quartile-based adjustment values from the original lidar DEM. A random forest regression model achieved the highest pseudo R2 value of 0.94 for predicting biomass density in g/m2. The adjusted DEM based on the estimated biomass densities reduced the root mean squared error of the original DEM from 0.38 m to 0.18 m while decreasing the raw mean error from 0.33 m to 0.14 m, improving both measures by 54% and 58%, respectively.

Thesis (M.S.)--Baylor University, 2009. / Includes bibliographical references (p. 61-67).

Annual allochthonous leaf litter inputs to temperate headwater streams provide a major contribution to the energy and carbon dynamics of the system, with whole seasonal cycles being determined by leaf litter inputs. Although a number of different physical and hydraulic factors have been linked to leaf retention, the mechanism of leaf retention has not been fully quantifed. A series of flume experiments investigated how leaf retention and the flow structure varied with bed heterogeneity, boulder submergence and boulder density. Two set-ups were used; a flat bed consisting of two physically different substrates, sand and pebbles, under the same `global' conditions and an idealised situation using uniformly sized concrete hemispheres placed in a staggered array directly on the flume bed, where the boulder submergence and density was varied systematically for a constant discharge. Saturated leaves were added, with retention number and locations being recorded. Detailed three dimensional velocity measurements were taken throughout a control volume. Signifcantly higher retention was observed on the larger substrate and the presences of protrusions were found to be important. Boulder density was signifcantly related to both the retention effciency and retention per boulder with an optimum density occurring at the intermediate density. Flow depth was found not to be signifcantly related to any measure of retention. The presence of the boulders generated a number of previously identified coherent structures within the flow. Increase in boulder density produced larger wakes, stronger crossstreamwise and vertical velocities and increased TKE within the boulder flow layer. The flow structure did not change with boulder submergence but with increasing boulder density it changed from isolated boulders with separate wakes to wake-interfering flow where the wakes of adjacent boulders were observed to `overlap'. A strong relationship was exhibited between the spatially-averaged near-bed shear stress immediately upstream of the boulder and retention. Retention increased as the shear stress neared zero, and decreased with both large negative and positive shear stresses. Maximum retention occurred under isolated flow conditions, with an increase in density providing increased retention due to a greater number of retention locations. However, a change in flow conditions to wake-interaction resulted in a decrease in retention.

This research work is aimed at developing a coupled surface-groundwater flow model which can be used to simulate both surface and groundwater flow at the swash zone. The coupled model is then used to investigate the effects of seepage on swash hydrodynamics as well as morphodynamics. The surface flow model was originally developed by Briganti et al. (2012), which solved a system of equations consisting of the Nonlinear Shallow Water Equations and the bed-evolution (Exner) equation with bed shear stress computed using a boundary layer model without seepage developed in Briganti et al. (2011). In this work, a groundwater flow model which solves Laplace's equation following the approach of Li and Barry (2000) is incorporated into the surface flow model, which allows computation of seepage into the bed (infiltration) and out of it (exfiltration). The seepage is then included into the boundary layer models to incorporate the effects of seepage on the bed shear stress. To assess the performance of the surface flow model, dam-break cases are simulated and compared against analytical and quasi-analytical solutions from literature. Firstly, the dam-break case on a fixed bed is simulated and compared against Ritter solution (Stoker, 1957) and then the dam-break case on a mobile bed is verified against Zhu (2012)'s quasi-analytical Riemann solver. Both models show good agreement with their respective reference results. Subsequently, the verification of the groundwater flow model is conducted by simulating phreatic surface flow through a rectangular dam and comparing the results against those of Kazemzadeh-Parsi and Daneshmand (2012). Next, the coupled surface-groundwater flow model is validated by reproducing surface and groundwater flow in the prototype-scale BARDEX II experiment. Firstly, the groundwater flow cases (higher and lower lagoon levels than the initial sea level) without surface water waves are simulated. The comparison of time-averaged numerical phreatic surface elevations against the experimental data shows excellent agreement. Next, the surface water waves are included and the simulations are repeated for the previous two cases. The groundwater comparisons again yield good agreement and the hydrodynamics of the surface waves show reasonably close agreement. Increase in exfiltration is observed to result in an increase in boundary layer thickness, which subsequently results in smaller velocity gradients and a decrease in bed shear stress using exfiltration included BBL model of Cheng and Chiew (1998). Conversely, the increase in infiltration causes a decrease in boundary layer thickness, which results in an increase in bed shear stress using infiltration included BBL model of Chen and Chiew (2004). The model results also show that the boundary layer effect by infiltration is opposed by the 'continuity effect' in the swash zone (Baldock and Nielsen, 2009). The model results show that an increase in infiltration rates is observed to increase slip velocity, and also compares well against the empirical equation derived in Chen and Chiew (2004). Furthermore, the rate of increase (decrease) of bed shear stress due to infiltration (exfiltration) compares favourably against the empirical trend line of Nielsen et al. (2001) and experimental data of Conley (1993). Additionally, the boundary layer model bed shear stress is compared against single swash event bed shear stress results from Kikkert et al. (2013) experiment and shows reasonably good agreement. The boundary layer models can be used to account for seepage effects on bed shear stressfor a larger range of ventilation parameters than Nielsen et al. (2001), which would improve morphodynamical modelling on permeable beds in the swash zone. Finally, the performance of the coupled surface-groundwater model is further investigated by simulating the BARDEX II experiment with a mobile bed. The swash zone water depth compares well with the BARDEX II experimental results. Although the corresponding dataset for velocity is shown to be rather unreliable during backwash, during uprush, the comparison is very close. Using both Meyer-Peter-Müller (MPM) and Grass sediment transport models, similar morphodynamical patterns are observed. The bed change comparisons against experimental results show that the model predicts the same order as well as the same pattern of erosion. However, deposition in the upper swash zone is not predicted by the model which could be due to the presence of significant amounts of suspended sediment which would lead to onshore sediment transport (Pritchard and Hogg, 2005, Zhu and Dodd, 2015) which is not accounted for in the simplified numerical model. The model is shown to be robust and flexible and it is capable of simulating both surface and groundwater flow simultaneously on fixed or evolving bed.

This study had three primary aims. Firstly, to establish the flow resistance characteristics of meandering channels in flood with different inner channel sinuosities and morphology. Secondly, to gain a better understanding of the coherent flow structures and energy loss mechanisms present within such flows. Third, to establish a link between the identified energy loss mechanisms and the flow resistance behaviour of channels with different geometry. The study begins with a review of current literature appertaining to three flow systems. These were; Inbank flow through meandering channels, overbank flow through channels comprising a straight channel with straight parallel floodplains, and meandering channels with floodplain flow. The available literature with regards to flooded meandering channels was limited to a handful of studies. It was clear there existed a deficiency in stage-discharge data over a range of inner channel sinuosities, and the flow descriptions given were limited to inner channels of relatively low sinuosity i.e. 1.25 - 1.3, rectangular or trapezoidal cross-section and unrealistically low width to depth (aspect) ratio. In addition, the influence of roughened floodplains also required further study. To address these needs, a small-scale laboratory investigation was undertaken at Aberdeen, together with a large-scale collaborative experimental study centred at the SERC Flood Channel Facility. These two experimental studies, in which two inner channels of sinuosity 1.4 and 2 were investigated in detail, are described. The experimental techniques and data collection procedures used are also described. The data types collected include: stage- discharge data, flow visualisation, flow velocity measurement, water surface profiles and bed shear stress analysis using an erodible bed. The stage-discharge data were used for the following; to establish the relationship between inner channel sinuosity and overall channel flow resistance; to establish the effect of inner channel morphology on overall channel resistance: and to assess the implications of roughened floodplains on resistance behaviour. The analysis of these data, together with existing related overbank data, yielded a number of conclusions; i). Overall flow resistance increases as inner channel sinuosity increases, ii). At deep floodplain flows, a floodplain comprising a trapezoidal inner channel was less efficient than one comprising a smaller natural inner channel, iii). Roughening the floodplains has a significant effect on channel resistance characteristics. The flow description data, of overbank flow, revealed the presence of coherent flow structures in flows over inner channels of sinuosity 1.4 and 2, and at a number of flow depths. It is suggested these coherent flow structures are a source of additional energy loss, and a link is proposed between the vigour and frequency of these structures for several flow conditions and channel geometries, and the overall resistance behaviour. Contour maps of water surface elevation are presented for several flow conditions and channel geometries. An increase in surface relief was observed as floodplain depth, and therefore velocity, increased. These maps and earlier related work were then discussed. Plots of near bed velocities, secondary circulation patterns and erodible bed observations strongly indicated a change in sediment erosion and deposition patterns, and thus a change in inner channel morphology during overbank flow. Implications of this change are proposed and discussed. Finally, suggestions for future work are presented. with particular emphasis on a 3-dimensional numerical model presently under development at the University of Aberdeen.

No abstract available. / Thesis (Ph.D.)-University of Natal, Durban, 1984.

No description available.

No description available.