CAREER: A mechanistic understanding of sediment transport in mountain streams with applications in river restoration and science education
In mountainous drainage basins, steep channels (gradients of 3-20%) occupy the majority of the total channel length and influence the downstream delivery of sediment and water to metropolitan areas and hydropower facilities. The volume and grain sizes of sediment supplied from these streams also impact the success of downstream river restoration projects. Basin-scale sediment transport predictions are needed in restoration design to account for the effect of sediment supply on aquatic habitat, water quality, and channel stability. Most sediment transport equations are based on empirical fits to data measured at the reach-scale, do not include the mechanics of grain motion, and were developed for lower-gradient channels. It is hypothesized that bedload transport equations for steep, rough streams need to include: 1) the range of turbulence and grain properties that control the initiation of grain motion, 2) the spatial variability in stresses and bedload transport rates on patches, and 3) the effect of temporal and spatial variations in sediment supply. Flume experiments will be used to test this hypothesis, further elucidate the interaction between turbulence and bedload transport, and inform theoretical and empirical models that predict sediment flux at the reach scale. Such models will be tested in local and international field locations and will transform predictions of landscape evolution and river restoration design by providing accurate and mechanistic estimates of sediment flux in steep streams. The intellectual merit of this research is a fundamental and predictive understanding of the processes that control turbulence and sediment transport in steep streams. The framework of sediment transport and river restoration will be used to educate graduate, undergraduate, and K-12 students on the importance of water resources and functioning stream ecosystems. Four education objectives are proposed: 1) a series of graduate student classes that develop critical thinking, scientific writing, and interdisciplinary team skills, 2) international research experience for undergraduate and graduate students, 3) programs to educate K-12 students on river processes, and 4) a new Women in Science Camp that encourages young women to enter careers in math, science, and engineering.