abstract: The Phoenix Metropolitan region is subject to intense summer monsoon thunderstorms that cause highly localized flooding. Due to the challenges in predicting these meteorological phenomena and modeling rainfall-runoff transformations in urban areas, the ability of the current operational forecasting system to predict the exact occurrence in space and time of floods in the urban region is still very limited. This thesis contributes to addressing this limitation in two ways. First, the existing 4-km, 1-h Stage IV and the new 1-km, 2-min Multi-Radar Multi-Sensor (MRMS) radar products are compared using a network of 365 gages as reference. It is found that MRMS products consistently overestimate rainfall during both monsoonal and tropical storms compared to Stage IV and local rain gauge measurements, although once bias-corrected offer a reasonable estimate for true rainfall at a higher spatial and temporal resolution than rain gauges can offer. Second, a model that quantifies the uncertainty of the radar products is applied and used to assess the propagation of rainfall errors through a hydrologic-hydraulic model of a small urban catchment in Downtown Phoenix using a Monte Carlo simulation. The results of these simulations suggest that for this catchment, the magnitude of variability in the distribution of runoff values is proportional to that of the input rainfall values. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2020

The development of regional flood-frequency equations is a key component of engineering infrastructure design and flood risk assessment at ungauged sites. These equations are constructed based on regression analysis techniques to study the connection between peak flow observations and different explanatory variables. However, many regions of the world remain poorly gauged or have experienced dramatic changes in land use or climate that make past observations less useful. To remedy this situation, we need to interpret and construct these regional equations based on physical principles of water movement and general knowledge of the geographic and geomorphologic setting of the upstream catchment at the location of interest. Several studies have examined these regional equations through the scaling theory of floods, making physical interpretations of the equation parameters (or scaling parameters) with respect to rainfall properties and geomorphologic variables. However, despite the advances of these previous works, the scaling theory of floods must be concerted with different, well-known problems in statistical hydrology for a proper engineering application in flood regionalization. These problems can vary from limitations in peak flow observations (sampling errors) to selection of an inadequate model structure of peak flows (epistemic errors). I present a series of studies based on hydrologic simulations and peak flow observations that illustrate several aspects related to the application and use of the scaling theory of floods, which include the following: (1) description of spatial patterns of scaling parameters; (2) inclusion of river network descriptors in flood frequency equations; and (3) evaluation of sampling errors and epistemic errors in the construction of flood frequency equations. The results presented in this dissertation contribute to the development of a more complete regional flood frequency analysis framework that leverages the physics of peak flow scaling and river network descriptors.

Simulating the processes of rainfall and runoff are at the core of hydrologic modeling. Geomorphologic features, rainfall variability, soil types, and water table depths strongly influence hydrological process in Florida ecosystems. Topographic characteristics of the terrain define the stream paths and landscape. Alteration of these characteristics as a result of urban and/or agricultural developments, for example, can highly influence wetlands and river basin response. There are two predominant landforms in Florida: wetlands, where Variable Saturated Areas form near streams causing saturation excess runoff, and uplands where runoff is mainly generated by infiltration excess. The objective of this work is to analyze the impacts of geomorphologic and hydrologic characteristics on runoff mechanisms in humid environments such as Florida. In general, most research at the hillslope scale use hypothetical values of rainfall, sometimes non-realistic values, and single slope forms to explain the geomorphic and hydrologic process on Variable Saturated Areas. In this thesis, the complexity of hillslope processes on actual Florida topography is assessed by coupling a Digital Elevation Model with a two-dimensional variable saturated-unsaturated flow model called HYDRUS-2D. Actual rainfall records and soil parameters from the Characterization Data for Selected Florida Soils, Soil Survey were used to evaluate hydrologic impacts. A commercial software package, River Tools was used to display and extract topographic information from the Digital Elevation Models. Results show that when inflitration excess runoff is dominant, infiltration and runoff are very sensitive to time resolution, especially for convective storms. When saturation excess occurs, runoff is not affected by rainfall intensity. However, saturated hydraulic conductivity, depth to the water table, slope and curvature highly influence the extent of Variable Saturated Areas. Results indicate runoff in shallow water table environments is produced mainly by subsurface storm runoff, running below the surface, except in hillslopes with concave curvature and mild slopes. Additionally, concave hillslopes generate more saturation excess runoff than straight and convex hillslopes.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18555号 / 工博第3916号 / 新制||工||1602(附属図書館) / 31455 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 立川 康人, 教授 戸田 圭一, 准教授 KIM Sunmin / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Globalization is a rapidly increasing trend in many industries, including civil engineering. This paper defines the skills engineers will need in an increasingly international industry. It also describes an engineering study abroad program designed to teach some of those skills to students and presents a survey used as an assessment tool to evaluate the effectiveness of the program. The program, called Mexico Engineering Study Abroad (MESA), is taught at Brigham Young University (BYU) in Provo, UT. MESA is a project-based extended field trip format class that couples hydrologic modeling with cultural awareness as students work together with Mexican students on water resources modeling projects in Mexico. The aforementioned survey shows that MESA affects a positive change in the student development and importance of global engineering skills such as leadership, teamwork, cultural sensitivity, and language. The importance of these skills in the workplace was also measured. The data shows that MESA is effective at developing global engineering skills in students. The data also suggest that other schools could use MESA as a model for their own efforts to prepare students for a more global industry. They show that non-technical skills can be measured and the results used to improve the course and the assessment methods. In particular, the MESA course could be improved by involving more faculty and increasing parity between the BYU and Mexican experiences in the course. The survey can be improved by conducting pre-class and post-class surveys instead of just one post-class survey. A special effort should be made to develop symmetry of experience for Mexican and BYU students, including extending the survey to the Mexican students.

The goal of hydrologic models is to accurately predict a future event of a given magnitude. Historic data are often used to calibrate models to increase their ability to forecast accurately. The GSSHA model is a distributed model that uses physical parameters and physics based computations to compute water flow from cell to cell based on a 2 dimensional grid. The goal of calibration is to obtain good estimates for the actual parameters of the watershed. These parameters should then transfer to other storm events of different magnitudes more easily than an empirical model. In conducting this research three watersheds were selected in different parts of the United States and the required data were collected to develop and run single event hydrologic models. The WMS software was used to preprocess digital spatial data for model creation before calibrating them with the GSSHA model. A calibrated HEC-HMS model was also developed for each watershed for comparative purposes. Establishing GSSHA's usability in routine hydrologic modeling is the primary objective of this research. This has been accomplished by developing guidelines for GSSHA calibrations, assisted by WMS, testing model accuracy in the calibration and verification phases, and comparing results with HEC-HMS, a model widely accepted for routine hydrologic modeling. As a result of this research, the WMS interface has become well equipped to set up and run GSSHA model calibrations. The focus has been on single event, or routine hydrologic model simulations, but continuous simulation calibrations, an important strength of GSSHA, can also be developed. Each of the model simulations in the study calibrated well in terms of matching peak and volume. However, the verification for two out of the three watersheds used in the study was less than ideal. The results of this research indicate that the physical factors, which GSSHA should represent well, are particularly sensitive for single event storms. The use of calibration of single events is therefore difficult in some cases and may not be recommended. Further research could be done to establish guidelines for situations (e.g. watershed conditions, storm type, etc.) where single event calibration is plausible.

Empirically based lumped hydrologic models have an extensive track record of use where as physically based, multi-dimensional distributed models are evolving for various engineering applications. Despite the availability of high resolution data, better computational resources and robust numerical methods, the usage of distributed models is still limited. The purpose of this research is to establish the credibility and usability of distributed hydrologic modeling tools of the United States Army Corps of Engineers (USACE) in order to promote the extended use of distributed models. Two of the USACE models were used as the modeling tools for the study, with Gridded Surface and Subsurface Hydrologic Analysis (GSSHA) representing a distributed and with Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) representing a lumped model. Watershed Modeling System (WMS) was used as the pre- and post-processing tool. The credibility of distributed models has been established by validating that the distributed models are efficient in solving complex hydrologic problems. The distributed and lumped models in HEC-HMS were compared. Similarly, the capabilities of GSSHA and lumped models in HEC-HMS in simulating land use change scenario were compared. The results of these studies were published in peer-reviewed journals. Similarly, the usability of the distributed models was studied taking GSSHA-WMS modeling as a test case. Some of the major issues in GSSHA-modeling using WMS interface were investigated and solutions were proposed to solve such issues. Personal experience with GSSHA and feedback from the students in a graduate class (CE531) and from participants in the USACE GSSHA training course were used to identify such roadblocks. The project being partly funded by the USACE Engineering Research and Development Center (ERDC) and partly by Aquaveo LLC, the research was motivated in improving GSSHA modeling using the WMS interface.

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