The goal of my dissertation was to describe the dynamics of a group of Houston toads located at the Griffith League Ranch (GLR), Bastrop County, Texas. My research included using statistical modeling to predict activity and abundance, mark-recapture techniques to estimate survivorship, and simulation modeling to explore the impacts of the difference in age at first reproduction and to project the future dynamics of the population at the GLR. From 2001 – 2005, 225 individual Houston toads (199 M : 26 F) were captured using two methods: breeding pond surveys and drift fences. Houston toads were neither caught equally among capture methods, nor across years. Toad activity was mostly confined within their breeding season, and activity was not continuous. A logistic regression indicated activity depended on time of year, mean precipitation, mean minimum daily temperature, and mean percent lunation as well as two-way interactions with moon-phase and other variables. Abundance depended on time of year, current precipitation, minimum temperature, and two-way interactions between time of year and the other two variables. Twenty-one of the 199 males (10.5%) and no females were recaptured among years. The probability of male survival was estimated using program MARK. Eight of 16 candidate models were supported and all but one contained precipitation as a covariate, indicating precipitation is important for Houston toad survival. Survivorship estimates varied from 0.1 to 0.41. The sex ratio was significantly male-biased. The odds of catching females in traps were 3.5 greater than capturing females in a pond, while the odds of capturing males in a trap were 0.28 compared to ponds. Results from a simulation model indicated the sex ratio is biased because of the difference in maturation times between males and females, coupled with high juvenile mortality. Results from an individual-based, spatially-explicit, stochastic simulation model, indicated a relatively low probability (~ 0.013) of B. houstonensis going extinct at the GLR within the next 10 years. Emergent properties of the model were similar to results observed in the field or reported in the literature. The model also identified that dispersal of Houston toads should be a future research priority.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (D. Ed. Min.)--Southwestern Baptist Theological Seminary, 2007. / Includes bibliographical references (leaves 264-273).

Heterogeneous reactions have the potential to significantly impact urban ozone formation and total reactivity of the atmosphere. This dissertation used comparisons between photochemical modeling predictions and field measurements to examine heterogeneous N₂O₅ chemistry in Southeast Texas. Heterogeneous reactions of N₂O₅ can lead to two different products: nitric acid (HNO₃) and nitryl chloride (ClNO₂). The formation of HNO₃ results in a loss of reactive nitrogen from the atmosphere. In contrast ClNO₂ photolysis forms Cl radicals and NO₂, both of which promote ozone formation in the troposphere. Preliminary modeling identified key uncertainties and the need to perform more refined modeling which included updated PM emissions estimates, an updated gas-phase N₂O₅ hydrolysis reaction rate constant, updated reactive uptake coefficients, and the inclusion of ClNO₂ as a product of heterogeneous N₂O₅ uptake. Refined modeling which incorporated all of these improvements was carried out and was the first comprehensive modeling of this chemistry performed for an urban air pollution episode. Comparisons of aerosol surface area concentrations, N₂O₅ concentrations, HNO₃ concentrations, and ClNO₂ concentrations with ambient data showed that model predictions were reasonable. The exceptions to this were 1) over-predictions of aerosol surface area concentration peaks at altitudes above 1500 meters and 2) over-prediction of N₂O₅ concentrations in the Houston Ship Channel. Further analysis is needed to identify the reasons for these over-predictions. Other key findings from this modeling include the model prediction of inland chlorine concentrations high enough to form ClNO₂ and the prediction that a large portion of atmospheric chlorine is cycled through ClNO₂, therefore making the inclusion of ClNO₂ into photochemical models essential for properly simulating chlorine chemistry. In addition, modeling suggested that the chemistry leads to significant increases of NO[subscript x] at night, but decreases in daytime NO[subscript x] concentrations and that the overall effect was to decrease ozone concentrations. Further investigation into the effect of ClNO₂ as a chlorine source showed that likely ozone increases in the Houston area caused by the presence of this compound are on the order of several ppb. Further analyses showed that vertical dispersion and local atmospheric composition moderated the effect of nitryl chloride on ozone mixing ratios. / text

This study focuses on solutions for the specific issues experienced by the distance learning program at the Lone Star College System (LSCS), a multi-college community college district located north of the Houston metro area. Utilizing practical action research methodology, the purpose of this study is to explore options for improving the LSCS distance learning program to better meet the needs of current and future distance learning students. This study combines a review of literature, local insights concerning the LSCS distance learning program, and discussions with other community college distance learning practitioners around the country for the purpose of developing an administrative proposal for the LSCS distance learning program. The study involves an exploration of the administrative and governance structure, a review of services provided to distance learning faculty and students, and an examination of quality standards for online courses and services. / text

The 4-step process has been the standard procedure for transit forecasting for over 50 years. In recent decades, researchers have developed ridership forecasting regression models as alternatives to the costly and time consuming 4-step process. The model created by Lane, DiCarlantonio, and Usvyat in 2006 is among the most recent and most widely accepted. It includes station area demographics, central business district (CBD) employment, and the station areas’ built environments to estimate ridership. This report applies the Lane, DiCarlantonio, and Usvyat model to the North Line of Houston’s Metropolitan Transit Authority of Harris County (METRO). The report compares the 2030 ridership forecast created by METRO using the 4-step process with the LDU model forecasts. For the 2030 projections, this report obtained population and employment estimates from the Houston-Galveston Area Council and analyzed the data using Esri ArcMap and Caliper TRANSCadGIS software programs. The LDU model produced unrealistically high ridership numbers for the North Line. It estimated 108,430,481 daily boardings. METRO’s 4-step process predicted 29,900 daily boardings. The results suggest that the LDU model is not applicable to the Houston light rail system and is not a viable alternative to the 4-step process for this specific metropolitan area. The LDU method for defining Houston’s CBD was the main problem in applying the model. It calculated an extremely high CBD employment density compared to other cities of similar size. Even when the CBD size was manipulated to decrease employment density, the model still predicted 212,210 daily boardings for the North Line, nearly 10 times higher than METRO’s 4-step process estimate. In addition to the problems with the definition of the CBD, the creators of the LU model did not specifically explain how to define a metropolitan area. Multiple inconsistent and subjective definitions of a metro area can be used. This report employs three different definitions of the Houston metro, all of which produced three significantly different ridership forecasts in the LDU model. As a result of these flaws, the LDU model does not accurately apply to METRO’s North Line, and it does not serve as a viable alternative to METRO’s 4-step process. / text

This report examines the potential benefits from the redevelopment of landfills into parks in Houston, Texas. Many Park and Recreation (P&R) Departments are unable to acquire and develop parkland at a rate on par with new residential construction. Parks provide economic, environmental, public health and aesthetic benefits. Despite these benefits, P&R Departments are often the target of budget cuts when city governments grapple with funding shortfalls. P&R Departments must pursue low value lands to meet parkland needs. Closed Municipal Solid Waste (MSW) landfills are a source of low value land in, and surrounding urban areas. New regulatory framework in the form of the U.S. EPA’s Municipal Solid Waste Landfill Criteria ensures closed landfills may be safely and cost effectively redeveloped for recreational use with limited liability concerns for the P&R Department. This regulatory framework is discussed and Best Management Practices (BMPs) are outlined. These BMPs focus on accommodating the dynamic nature of landfills to minimize park development and Operation and Maintenance (O&M) costs. The substantial parkland deficit in the City of Houston is quantified. The findings of the needs assessment in the City’s Parks Master Plan are presented. A multi-tiered Geographic Information Systems (GIS) based analysis is utilized to evaluate the potential benefits from the redevelopment of existing landfills in the City into parks. The GIS analysis identified 8 landfills that, if redeveloped, will increase the distributional equity of City parkland holdings. Of these 8, the 4 landfills with the lowest expected total development costs and the highest expected savings over traditional greenfield development were identified. It is recommended the City adopt a thorough site characterization and planning process and pursue landfill redevelopment as a cost effective and beneficial way to increase parkland holdings. / text

A vessel-mounted ADCP study focusing on channel-scale flow patterns in Galveston Bay near the Houston Shipping Channel and Mid-Bay Island is described. Winds of 5-7 m/s at 215-230◦ from N were present during data collection. For both peak ebb and flood conditions, the tidal circulation forced flow in a direction opposing the wind, perhaps due to a large-scale flow divergence forced by Mid-Bay Island. The strongest such currents were measured closest the island. During peak flood flow, the shape of the along-channel velocity profile for the open water upwind of the channel at Mid-Bay Island indicated uniform flow, and the salinity profile indicated a well-mixed water column. The near-island along- channel velocity profile showed a near-linear trend, and the salinity profile indicated a stratified water column. This suggested that the stratification had some effect the velocity profile shape, but further research is needed to better quantify this effect. During peak ebb flow, the near-island along-channel velocities were highly variable with respect to the mean velocity, indicating an area of active turbulence. Salinity profiles collected in the open water and near-island both showed stratification, something that was not seen during flood conditions. Differences in observations between flood and ebb flows can possibly be attributed to the survey location with respect to the chain of dredge spoil islands. During flood flows Mid-Bay Island is the first of the islands, and the flows surrounding the island may part of a developing horizontal boundary layer. During ebb flows the island is last in the chain relative to the direction of flow, and therefore the surrounding flows are well back from the leading edge of a horizontal boundary layer. / text

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