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Master of Science in Engineering - Engineering / There have been various threats from upstream catchment developments to the water supply of the ecologically important Nylsvlei floodplain in South Africa. Hydrological modelling of the catchments and unsteady hydraulic modelling of the floodplain (including measured losses to evapotranspiration and infiltration) with biotic links to Oryza longistaminata revealed that existing developments within the catchments have decreased areas suitable for growth of this plant in the Nylsvley Reserve by 9% on average from 1973/74 to 2000/01 compared to the catchment in a virgin state. Construction of the proposed Olifantspruit Dam with environmental flow releases would have reduced these suitable areas by a further 9% on average. Catchment developments were found to have the greatest impact on floodplain inundation in average to dry years and would also reduce the frequency of occurrence of suitable conditions for growth of Oryza longistaminata.

No description available.

No description available.

Improvements in the strength and durability of frost-susceptible soils and aggregates can be achieved through chemical stabilization using portland cement, where the efficacy of cement stabilization for improving durability depends on the degree to which hydraulic conductivity is reduced. Hydraulic conductivity is commonly estimated from basic soil properties using Moulton's empirical equation. However, the hydraulic conductivity estimation does not consider the detrimental effects of freezing or the benefits of cement stabilization. The purpose of this research was to derive new equations relating hydraulic conductivity after freezing to specific material properties of cement-treated soils and aggregates stabilized with different concentrations of cement. This research included material samples from two locations in Alaska and from single locations in Minnesota, Montana, Texas, and Utah, for a total of six material samples. Each soil or aggregate type was subjected to material characterization by the Unified Soil Classification System (USCS) and the American Association of State Highway and Transportation Officials (AASHTO) classification system. Moisture-density curves were developed, and unconfined compressive strength (UCS) testing was performed to determine cement concentrations generally corresponding to low, medium, and high 7-day UCS values of 200, 400, and 600 psi, respectively. After being cured for 28 days at 100 percent relative humidity, the prepared specimens were subjected to frost conditioning and hydraulic conductivity testing. The Alaska-Elliott, Minnesota, Montana, and Utah materials exhibit decreasing hydraulic conductivity with increasing UCS, the Texas material exhibits increasing hydraulic conductivity with increasing strength from the low to medium cement concentration levels but decreasing hydraulic conductivity from the medium to high cement concentration levels, and the Alaska-Dalton material exhibits increasing hydraulic conductivity with increasing strength. Multivariable regression analyses were performed to investigate relationships between hydraulic conductivity and several material properties, including soil gradation and classification, fineness modulus, specific gravity, cement content, porosity, compaction method, dry density, and 7-day UCS for each specimen. The R2 values computed for the six-parameter, four-parameter, USCS, and AASHTO-classification models are 0.795, 0.767, 0.930, and 0.782, respectively. Further research is recommended to investigate the effects of cement on hydraulic conductivity for USCS and AASHTO soil types not covered in this research.

The Arroyo Grande Creek Watershed, an approximately 170 mi2 watershed located on the central coast of California, drains to the Pacific Ocean via the Arroyo Grande Creek that passes through several coastal cities including the community of Oceano. At the mouth of the Creek is the Arroyo Grande Lagoon, which is connected to another lagoon known as the Oceano Lagoon, by a tidal flap-gate whose hydraulics is a function of water levels in the two lagoons. Historically the Oceano Lagoon has played a part in floods that have occurred in the community of Oceano. The most recent flooding occurred in 2010 when a storm with about a10-yr frequency caused flooding that led to an estimated property damage of about two million dollars. This study was conducted to understand hydrology of the Arroyo Grande watershed that also feeds Lopez Lake, a reservoir that provides water for drinking, agriculture, and environmental flows; to characterize hydraulics of the Oceano Lagoon; and to explore scenarios for flood mitigation. Objectives of the study are to provide a better understanding of the causes of the historical floodings; map the extent of floodings for various storm events including 10 year, 50 year, and 100 year under current conditions; and examine potential solutions to reduce future floodings. Surface water hydrology of the Arroyo Grande Creek Watershed was studied using HEC-HMS to quantify runoff specifically into the Oceano Lagoon. HEC-HMS was calibrated using known streamflow to improve the accuracy of the model. The HEC-HMS model was developed using spatial data that was organized in ArcMAP. Data such as elevation, land use, soil type, and impervious surface were processed using HEC-GeoHMS and exported to HEC-HMS. Mitigation measures were simulated in HEC-HMS by adjusting parameters such as the outlet configuration and the increased volume in Oceano Lagoon. Each mitigation measure delivered varying effectiveness. Results show that while the peak flow and volume in the lagoon can be reduced, larger design storms will continue to inundate the area unless drastic steps are taken. The findings could assist local flood control agencies by evaluating the risks of continuing to use the existing drainage system, and identifying opportunities available to reduce those risks.

Although regulations and requirements for water quality source monitoring have increased, drinking water distribution systems can still be considered vulnerable to purposeful or accidental contamination. This study analyzes the transport of the hypothetical contaminant Cryptosporidium through the distribution system of a city with a population of 30,000 to 50,000 in an attempt to locate the optimal monitoring locations in the distribution system. Cryptosporidium was selected due to its resistance to chlorine and it’s conservative properties for vulnerability assessments. The method for selecting the optimal monitoring locations was taken from Chastain (2004) which developed and examined the method for a virtual city. However, Chastain did not apply the method to an actual city. This study looks to use Chastain’s method conjunctively with WaterCAD® and Excel in an attempt to accommodate to the small scale systems which are more vulnerable relatively speaking. The results of the analysis, shown in Appendices A and B, are grouped into zones of significance which contain a cluster of optimal points for placing water quality sensors. These zones of significance are to be taken as a guide for mitigating potential terrorist initiated events on the water distribution system.

The efficient delivery of potable water for a community through its distribution system has historically been the backbone of nearly all metropolitan developments. Much of these systems are comprised of pipe networks made of various materials including concrete, iron, PVC, and even steel. As these communities expand and urbanize, water demand and population density simultaneously increase. This develops higher strains and stresses in the community‟s water distribution network causing pipes to corrode, crack, or rupture prematurely while in service. As a result, the deterioration of water distribution systems in growing cities is increasingly becoming a major concern for our nation. There have been several publications on the subject of evaluating pipe conditions within a water distribution network that use statistical models, estimation, and other mathematical analyses. However, many of these publications are cumbersome and are difficult to understand from a non-engineering perspective. In order to simplify the evaluation process for all varying professions in a city‟s public works division, the primary objective of this study was to develop a user-friendly risk assessment model that was practical, cost effective, and easy to follow. This risk assessment model focuses primarily on the physical condition of pipes in a water distribution system. It assesses the installation year, age, material, and break history of these water mains. It does not consider pipe fittings, pumps, or other network components. A pipe‟s probability of failure is determined from its physical condition. Page v The model then considers various economic degrees of impact that may affect the rehabilitation or replacement of these water mains. These degrees of impact include raw material costs, customer criticality, land use, demand, pipe material, and traffic impact. By focusing on pipes having the highest probability of failure and considering their economic impacts, this model identifies and prioritizes the most vulnerable water mains that require immediate attention. In order to validate this developed risk assessment model, the method was applied to a real water distribution system. Data from the City of Arroyo Grande, California was used in conjunction with WaterCAD and geographic information systems (ArcGIS) software during analysis. Application of the risk assessment model identified six cast iron pipes in Arroyo Grande‟s water distribution system as having a high risk of failure. Of the city‟s 3,057 individual pipe segments, recognizing only five of these pipes as high risk indicated that the assessment model was functional. Developing and testing this risk assessment model with real city data effectively demonstrated its practicality and easy application to a real water distribution system. If utilized, city officials can quickly identify and prioritize pipes needing rehabilitation or replacement by using reliable, up-to-date water distribution data from their city with this risk assessment model. Furthermore, use of this model may also simplify allocation of capital funds for future pipe improvement projects as the city continues its urbanization.

Yes / Solutions for dam-break flow mainly developed for rectangular channels are not applicable to prediction of the propagation of the dam-break wave in frictional triangular channels. This study presents an approximate solution considering the frictional effect on the dam-break flow in a dry horizontal triangular channel. Wave tip velocity is solved by an implicit formula for the product of time and resistance coefficients. All other hydraulic properties in the wave tip region can be expressed as explicit functions of wave tip velocity. Meanwhile, laboratory experiments have been performed for obtaining water surface profiles of dam-break flow from which the position and velocity of the wave tip front have been derived. Results show that retardation of the wave front position is more significant with the increases in both resistance and time. The proposed analytical solution shows satisfactory agreement with measurements, and clarifies how the behavior of the dam-break wave tip is affected by channel geometry.

<p> A dissolved oxygen model for stratified lakes is developed and is verified for Lake Ontario. The processes affecting the dissolved oxygen budget of a lake including hydraulic inflow and outflow, production and decomposition, atmospheric reaeration, vertical transport across the thermocline, and sediment oxygen demand are analyzed and quantified. The production and decomposition oxygen fluxes are provided by a phosphorus model developed by others. These phosphorus-oxygen inter-relationships are quantified using stoichiometry developed for oceans. Nine years of temperature data for Lake Ontario are used to estimate the annual variations of epilimnetic temperatures, the rate of deepening of the epilimnion (i.e. thermocline depth vs time) and the vertical exchange coefficient. Dissolved oxygen data over a similar period are used to estimate lake-wide concentrations of DO. The vertical exchange and decomposition hypolimnetic oxygen fluxes are estimated from observed data. Model predictions of concentrations and fluxes compare favourably to the observed data. This provides some verification for the predictions of the oxygen model, the oxygen-phosphorus stoichiometry and the decomposition flux predicted by the phosphorus model.</p> / Thesis / Master of Engineering (MEngr)