Years participated in RESESS:
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Academic Affiliation: University of Idaho
Research Mentors: Greg Tucker
Communication Mentor: Jenny Nakai
Northern California was always a well-suited place for Amy’s development into a geologist. The majestic valleys, centuries-old redwood trees, and enormous mountain chains paved the way for her natural science passion. Amy is currently a recent graduate from the University of Idaho, studying mechanisms of flash flooding - specifically the spatial variability of runoff production and infiltration rates of soils for her RESESS research. Her project takes place in West Bijou Creek in east-central Colorado, where, armed with tipping-bucket rain gauges and sprinklers, she analyzed antecedent conditions for flash floods.
Mechanisms of flash-flood generation in a gullied high-plains grassland: evidence for partial contributing area runoff
Flash floods commonly cause rapid gully erosion, creating headwalls that erode into previously stable surfaces, thereby reducing arable land and releasing sediment that can contaminate water supplies. In semi-arid landscapes, gully erosion tends to be driven by flash floods. Here, we study the mechanisms for flash-flood generation, seeking to answer two questions: (1) how spatially variable is runoff production, and (2) what combination of rainfall intensity and duration is required to produce runoff? To answer these questions, we combine field data from a study site on the Colorado High Plains, USA, with numerical modeling. The site is characterized by patchy, dryland shrub vegetation dispersed throughout the otherwise bare slopes and gullies. Analysis of six years of rainfall and runoff data indicate that flash flood generation requires a 15-minute intensity of approximately 38 mm/hr. Sprinkler experiments on isolated bare and vegetated plots revealed a large contrast between infiltration capacities: bare areas can produce runoff when the rainfall exceeds 10-15 mm/hr, whereas vegetated areas permit infiltration of at least 45 mm/hr during relatively brief, intense events. These findings imply that high-intensity rainstorms associated with summertime moist convective systems drive gully incision. They also suggest that a self-enhancing feedback may exist in which initial incision creates steep and relatively bare slopes that tend to generate more runoff, leading to more aggressive gully incision.