It was in my freshman year at Princeton that I first experienced the dynamism of the Earth, traveling to eastern California for an introductory geology seminar. Roaming around the open expanses of the Owens Valley, I felt that the Earth had removed her mask, revealing crystallized lava flows, alluvial fans, and glacially carved valleys. Exploring the Mosaic Canyon in Death Valley, I could imagine the raging floods depositing conglomerate beds and cutting canyon walls into the gradually rising mountains. At the end of the freshman seminar, I wrote a paper on land subsidence in Mexico City caused by extraction of groundwater. Fascinated by the connection between human activities and underlying geological processes, my experience in the course led me to concentrate in Geological Engineering, and the research projects I pursued as an undergraduate reflected this interest in the human-geology connection. In the summer after my sophomore year, I researched strong ground motion and seismic site response through the Research Experience for Undergraduates (REU) program at University of Alaska-Fairbanks. During my senior year, I wrote my undergraduate thesis on the connection between air pollution and observed reductions in rainfall over Beijing, China. Among the things that I studied during college, I developed a particularly strong interest in rivers and streams. While spending a year studying at Nanjing University in China in 2005-6, I made friends with a hydrogeology student, Dong, who grew up in a small town not far from the Yellow River. As he grew older, Dong saw firsthand how industrialization caused the rapid degradation of the water supply in local streams and groundwater. While droughts became more common, floods also became more severe. Through meeting Dong, I became fascinated with the Yellow River and its historical record of capricious and destructive change. I learned that during the past three thousand years, the Yellow River has changed course at least fifty times, repeatedly building its channel to unstable levels due to the heavy load of sediment delivered from the intensively cultivated loess plateau in western China. Fascinated by fluvial geomorphology, in my junior year I pursued a research project on the effects of urbanization on Armory Run, a small storm drain fed stream on the Princeton University campus. I found that rapid conveyance of water through a buried network of tributary pipes effectively magnifies the effect of heavy rainfall, elevating peak discharges and causing rapid bank erosion and channel migration. Through a combination of field observations and modeling, I described this elevated hydrologic response and the deeply incised morphology of the stream channel. As an engineering student, the next obvious step in the Armory Run project was to design a solution to the erosion problem, which threatened an adjacent road and produced excessive sediment discharge into a downstream lake. In the fall of my senior year, I joined with three other engineering students to tackle this problem. While we considered drainage network changes that would slow the transport of rainwater into the stream, we decided to focus our efforts on the stream itself. We considered several physical changes to the stream, such as constructing meanders or adding roughening elements, which would dissipate flow energy and reduce the erosive force of the water. While instructive, we found that our attempts to design an effective restoration for the stream were hampered by our inability to reliably predict how the channel would respond to any possible changes (or how it would continue to evolve if we did nothing at all). A review of the literature on stream restoration revealed that current models of
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