The present research employs remote sensing data and advanced hydrologic modeling to improve the spatial representation of an urban watershed, Whiteoak watershed, located northwest of downtown Houston, TX. During the last thirty years, upstream Whiteoak experienced rapid growth that locally altered its topographic and hydrologic parameters through land use change and subsidence. This study examines whether land use change and subsidence contributed to the increased flooding occurrences of the last decade in the area, amplifying the impact of moderate and extreme rainfall events. Detailed digital elevation data acquired from a 2001 Light Detection and Ranging (LIDAR) survey of Harris County, NEXRAD radar rainfall data, satellite land cover data, historical areal photos, and subsidence contours provide the main topographic and hydrologic parameters that support the analysis. All data sets are compiled in a GIS environment, processed, transformed into grid format, and imported into a physics-based, fully distributed hydrologic model, Vflo(TM). After setting up and calibrating the Whiteoak Vflo model, the analysis focuses on an upstream area located in the center of the subsidence bowl. Quantitative results indicate that continuing subsidence since 1978 did not significantly impact the local peak flows. On the other hand, the combined effect of upstream channel modifications and land use change over the same time period increased considerably the peak flows at the 100 year level.

The USGS MOC Model is a useful tool for evaluating different well patterns in an aquifer restoration scheme under variable hydrogeologic conditions. The best well pattern for a groundwater cleanup is highly site-specific and depends upon the objectives and constraints for each problem. In this research, seven different well patterns were studied to determine which well pattern(s) is the most efficient in achieving a range of desired levels of contaminant reduction. The well patterns were evaluated on the basis of cleanup time, volume of water circulated and volume of water requiring treatment. Eight generic hydrogeologic conditions were modeled using different combinations of drawdown, hydraulic gradient and dispersivity. The key hydrogeologic variables which control the rate of cleanup are well locations, pumping rates, transmissivity, dispersivity and hydraulic gradient. For a given set of well locations, by varying transmissivity and maintaining drawdown, dispersivity and hydraulic gradient constant, the cleanup time was found to be inversely related to the pumping rate.

A reliability-based method for analyzing open drainage channels and detention basins using the full marginal distributions of uncertain parameters together with correlation coefficients will be presented in this work. A first and second order component reliability analysis will be performed using the computer program CALREL. Reliability results can be used both in performance and safety assessment of existing structures and in designing structures for a target reliability level. For the case of an open drainage channel, the computed reliability index will be compared with the usual safety factors of design, and a comparison will also be made of the reliability indices obtained using different runoff formulations. For the case of a detention basin, reliability results will be used as a design tool in the sizing of detention basins. The interaction of channels and basins will also be addressed.

The main objectives of this research are to propose a general stochastic method for determining analytically the distribution of flood volume, and to develop a simulation procedure for generating synthetic multiseason streamflows at different sites simultaneously. The research study is divided into two parts: (a) First, a general stochastic model is proposed to derive analytically the probability distribution function for flood volume. The volume of a flood is defined as the sum of an unbroken sequence of consecutive daily flows above a given truncation level. Analytical expressions were then derived for the exact distribution of flood volume for various cases in which successive flow exceedances can be assumed to be either independent or correlated, and the cumulative flow exceedance can be considered to be independent or dependent of the corresponding flood duration. The proposed stochastic method is more general and more flexible than empirical fitting approach because it can take explicitly into account different stochastic properties inherent in the underlying streamflow process. Results of a numerical application have shown that the proposed model could provide a very good fit between observed and theoretical results. Further, in the estimation of flood volume distribution, it has been found that the effect of the serial correlation property of the flow series is not significant as compared to the impact due to the dependence between flood volume and corresponding duration. Finally, it has been demonstrated that the simplistic assumption of triangular flood hydrograph shape, as usually appeared in previous studies, is not necessary in the estimation of flood volume distribution. (b) Second, a multivariate stochastic simulation approach is proposed for generating synthetic seasonal streamflow series at a single location or at many different locations concurrently. The suggested simulation scheme is based on the combination of the singular value decomposition

The application of a 2D hydraulic-habitat model, River2D, to simulate flows and fish habitat areas in a reach of the Nicolet River (Quebec, Canada) containing two sets of double-wing rock current deflectors to enhance fish habitat was examined. Depth-averaged velocity in the reach was determined using one or two measurement points in the vertical under the assumption that the profile was logarithmic; however, the presence of boulders and obstructions disturbed the profile, making it difficult to characterize using only two measurement points. The sensitivity of the simulation results to roughness characterization, topographic scale, mesh refinement, and boundary conditions was evaluated. The simulated and observed depths had correlation coefficients of 0.93 to 0.97, while the velocity correlation coefficients were 0.56 to 0.67. Qualitatively, the model accurately predicted the flow patterns, e.g. the recirculation zones downstream of the deflectors. Habitat suitability curves for brown trout, taken from literature, were used in the habitat model. Simulated discharges from 0.74 m3/s to 1.94 m3/s were critical minimum flows for suitable spawning brown trout habitat. The model was adequate for qualitatively simulating flow and habitat in this reach, however, the complex flow conditions may be better represented by a 3D model.

<p> Contaminants of emerging concern (CECs) are an unregulated suite of constituents frequently detected in environmental waters, which possess the potential to cause a host of reproductive and developmental problems in humans and wildlife. Degradation pathways of several CECs are well-characterized in idealized laboratory settings, but CEC fate and transport in complex field settings is poorly understood. In the present study I use a multi-tracer solute injection to study and quantify physical transport and photodegradation in a wastewater effluent-impacted stream in Ankeny, Iowa. Conservative tracers are used to quantify physical transport processes in the stream. Use of reactive fluorescent tracers allows for isolation of the relative contribution of photodegradation within the system. Field data were used to calibrate a one-dimensional transport model, and forward modeling was then used to predict the transport of sulfamethoxazole, an antibiotic in the effluent which is susceptible to photolysis. Results show that accurate predictions of reactive CECs at the scale of stream reaches can be made using the fate and transport model based on field tracer studies. Results of this study demonstrate a framework that can be used to couple field tracer and laboratory CEC studies to accurately predict the transport and fate of CECs in streams.</p>

This research deals with the estimation of rainfalls and floods for locations at which the corresponding data are unavailable (ungauged sites). The overall study can be divided into three different parts. The first part explores the validity of the distributional similarity of the rainfall time series aggregated at different time scales. Based on the theory of multiplicative cascade process, a scale independent mathematical model has been proposed to describe the probability distributions of rainfall time series aggregated at different time scales. It has been demonstrated that the multifractal formalism can be used to estimate the probability distribution of rainfalls for a wide range of space and time scales. / The second part of the research deals with the estimation of floods at an ungauged site using regional physiographic and climatic variables. To this end, a detailed study was carried out to determine the best technique for estimating the parameters of the commonly used power-form flood regionalization model, and to identify the minimum number of physiographic and hydrometeorological variables which should be included in the model. The study was further elaborated by applying the linear and nonlinear covariance structural models. Results of a numerical example using hydrologic data from Quebec and Ontario have indicated the superior performance of the nonlinear optimization method. Further, it was found that the significant variables which should be considered in the estimation of floods, are the area of the basin, the basin slope and the total precipitation five days before the flood for Quebec, and the area of the basin, the area of forests, lakes, and marses and the slope of the main channel for Ontario. / The third part of the study proposed a new method of flood estimation based on the scaling of the statistical moments of the regional flood series with the basin area. Analysis of the physiographic and hydrologic data from Quebec and Ontario showed that the non-central moments of order from one to six are scaling with the basin area. This empirical evidence was used in defining the hydrologically similar basins (i.e., homogeneous flood regions), and in selecting a suitable regional distribution function for the estimation of flood quantiles. It was observed that the grouping of homogeneous basins as proposed in this study formed well-defined geographical regions with distinct climatic characteristics. Further, it was recommended that the selection of regional probability distribution and the corresponding parameter estimation method should be made such that the scaling properties of the flood series were preserved. The improved estimates of the statistical moments and flood quantiles for unguaged sites have indicated the superiority of the proposed approach as compared to those values given by existing methods.

Thesis (Ph. D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references.

Thesis (M.S. - Hydrology and Water Resources) - University of Arizona. / Includes bibliographical references (leaves 54-59).

Thesis (M.Sc.)--University of Adelaide, 1959. / Typewritten.