No description available.

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.

The range of possible uses of inflatable hydraulic structures is very great provided a suitable design and analysis technique is available. The object of this project was to study both theoretically and experimentally the behaviour and performance of inflatable hydraulic structures under both hydrostatic and hydrodynamic conditions for dams inflated with air, water and a combination of the two. The theoretical analysis was based on a finite element approach to design a dam under different inflation fluids in order to find the dam parameters of tension, profile of the dam, upstream slope, and elongation of the material under both hydrostatic and hydrodynamic conditions. A series of models of different sizes were constructed and tested under both hydrostatic and hydrodynamic conditions. A comparison of different output parameters was carried out between the experimental and theoretical results showing a good relationship between the two. Relationships were derived so that the length of the membrane could be found for the design of a dam to satisfy particular conditions. A new formula was derived for calculating the rate of flow and coefficient of discharge for all three types of inflation allowing the application of inflatable dam as a device for measuring discharge. A range of computer programs was written for the analysis and design of all dams based on the finite element approach. This work was restricted to single anchor dams with the anchor located on the upstream side.

D.Sc. / Please refer to full text to view abstract

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, South Africa, in fulfilment of the requirements for the degree of Master of Science. 21 March 2016. / The problem of turbulent hydraulic fracturing is considered. Despite it being a known phenomenon, limited mathematical literature exists in this field. Prandtl’s mixing length model is utilised to describe the eddy viscosity and a mathematical model is developed for two distinct cases: turbulence where the kinematic viscosity is sufficiently small to be neglected and the case where it is not. These models allow for the examination of the fluid’s behaviour and its effect on the fracture’s evolution through time. The Lie point symmetries of both cases are obtained, and a wide range of analytical and numerical solutions are explored. Solutions of physical significance are calculated and discussed, and approximate solutions are constructed for ease of fracture estimation. The non-classical symmetries of these equations are also investigated. It was found that the incorporation of the kinematic viscosity within the modelling process was important and necessary. / MT2016

No description available.

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 has looked behind the mask of nineteenth-century theocracy to see Mormons in the Great Basin creating a democratic society of regionally concentrated kin groups where obligations and rewards for individuals were increasingly determined by age and life cycle position. As generations of young adults acted together in selfinterest dispersing their villages on receding frontiers, they forged a balance between competition and cooperation which merged the immediate need of individuals to establish and support families with the collective memory of their Mormon past. In so doing, they created an identity for themselves which was unique in the arid West. Residents of villages in Cache County, Utah, stratified by age as they worked to resolve the contradictions threatening their survival on the frontier. Initial settlers selected locations and built villages for efficient distribution of water. They tended to remain in their villages as they aged, slowly accumulating property while families grew to maturity. The number of residents increased through migration and high birth rates although village sites lacked sufficient water to sustain growth. Most village youth could not establish farms without migrating from home because the hydraulic structure of villages prevented spatial expansion. Many at maturity responded to the limits of water supply by building new villages and homesteads on northern frontiers, in Idaho during the early 1880s and in Canada and Idaho dry farms after 1900. They moved north in successive waves at quarter century intervals because baby booms following initial settlement clustered them in similar age cohorts. They began their own booms as they built communities on the frontier. The patterns of village maturation and age specific out-migration which sparked settlement in northern Utah, Idaho, and Canada were also at work in varying degrees in regions south of Salt Lake City--in southern Utah, Mormon Arizona, and Mexico. Throughout Mormondom, people responded to their own needs in lands of limited wealth. As they did, they created an ethnic identity which increasingly defined their range of options as they moved from one stage in the life cycle to another. (229 pages)

This study was part of the development of an ice jam flood forecasting system for Hay River, NWT. 2-D numerical models were used to simulate ice processes in an effort to predict ice jam formation. A summer survey was conducted to finalize the bathymetry of the Hay River Delta. Observations were undertaken during freeze-up and the winter to better understand Hay River ice conditions. Ice jam events were surveyed during breakup in 2008 and 2009 for model testing. The data collected was used to develop CRISSP2D and River2D models to simulate observed conditions. Simple tests were conducted with CRISSP2D to better understand the model inputs. CRISSP2D modeling of Hay River was unsuccessful and it limitations were discussed. River2D was able to match observed ice jam profiles. The results were used to create an Ice Jam Profile Generator to assist the Town of Hay River with evacuation planning. / Water Resources Engineering

The objective of this project was to design a prototype field air permeameter that can be used to track changes in the hydraulic conductivity within soil covers with time. The evolution of soil structure in reclamation soil covers at the Syncrude Canada Ltd. oilsands mine is currently being studied. The Guelph permeameter is currently used to measure hydraulic conductivity, but gathering the data is a very time consuming task due to the relatively low hydraulic conductivity of the cover materials. The use of a faster, more efficient method would increase the capabilities for tracking changes in hydraulic conductivity of reclamation soil covers with time. <p>Three air permeameter design options were evaluated. One design was chosen and a prototype was built. Preliminary field trials were conducted at the Syncrude Canada Ltd. oilsands mine in August 2005. Air permeability measurements were taken on various soil cover treatments and slope positions. Improvements to the air permeameter were implemented in 2006, and additional data gathered. Guelph permeameter testing was carried out alongside the air permeameter in both field seasons. The air permeameter and Guelph permeameter were also tested under controlled laboratory conditions and compared to standard constant head column tests. <p>Results include correlations of air and water permeability for various materials and soil structures. Using dry uniform sand in a laboratory setting, the full scale air permeameter provided permeability values within 21% of a standard constant head column test. Testing of the air and Guelph permeameters on a cover constructed of peat-mineral mix over tailings sand revealed a difference of approximately one order of magnitude in permeability values. A difference of approximately two orders of magnitude existed between permeability values measured with the air and Guelph permeameters on till/secondary soil covers. <p>Further investigation into the difference between values of permeability measured with both methods is necessary. If successful, the air permeameter could prove to be a viable alternative to the Guelph permeameter for use in long-term monitoring of soil covers used in mine reclamation or waste containment. A more efficient air permeability method would allow a greater number of measurements to be made in a shorter time and could be used to track temporal as well as spatial variability in hydraulic conductivity.