Adapting to Hydrologic Nonstationarity in Engineering Design
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The engineering design discipline of hydrology and hydraulics has, for the past several decades, been largely based on probabilistic design techniques involving recurrence interval storm and flood events. The engineering design storm and design flood have been enduring concepts; however, recently the concept of hydrologic nonstationarity has gained a foothold in engineering theory. An analysis of the annual maxima based method of predicting engineering design storms was conducted using multiple techniques to determine whether trends were detectable or prevalent. Analyses from over 300 rain gauge stations throughout the southeastern United States showed that over 40% had experienced some form of trending behavior over time. An analysis of tropical storm contributions to station annual maxima found that such events were not overly influential with regard to extreme event prediction. Furthermore, spatial trends were not detected. These findings showed that the engineering design storm is affected by hydrologic nonstationarity. This research also investigated several other sources of hydrologic nonstationarity – specifically, contributions from rapid urbanization, topographic subsidence, and engineering design decisions. Changes in engineering design flows from urbanization result in designs that are quickly obsolete and prone to inundation. The decisions of a design engineer can result in design flows vastly different from those predicted by hydrologic models, even when taking into account effects of suburban development. Additionally, the impacts of urban development, precipitation increase, and topographic subsidence were examined in concert in an attempt to quantify the individual impacts of each on potential flooded area. It was found that the three contributions of nonstationarity were individually quantifiable, and that the contributions from precipitation changes and topographic subsidence were the most significant sources. Land development was the least influential contributor, though still significant. Engineering design under changing hydrologic conditions will be one of the major challenges for the industry in the coming decades. This research examined several design techniques available in the literature and subjected them to quantitative and qualitative assessment measures to determine their performance under prevailing design assumptions. The assessment measures tentatively indicated that modular designs and designs based on the theory of ecosystem services may be most suitable under potential future hydrologic conditions.
Faloon, Anna Elizabeth (2015). Adapting to Hydrologic Nonstationarity in Engineering Design. Doctoral dissertation, Texas A & M University. Available electronically from