CAREER: A mechanistic understanding of sediment transport in mountain streams with applications in river restoration and science education

在山区流域，陡峭的河道(坡度为3-20%)占据了河道总长度的大部分，影响了下游泥沙和水向大都市区和水电设施的输送。这些河流提供的泥沙的体积和粒度也影响下游河流修复项目的成功。在恢复设计中，需要流域尺度的泥沙输移预测，以考虑泥沙供应对水生生境、水质和河道稳定性的影响。大多数泥沙输运方程是基于对河段尺度上测量的数据的经验拟合，不包括颗粒运动的力学，并且是为低坡度河道开发的。假设陡峭、粗糙河流的推移质输运方程需要包括：1)控制泥沙运动起始的湍流和颗粒特性的范围；2)应力和推移质输移率在斑块上的空间变异性；3)供沙的时空变化的影响。水槽试验将被用来验证这一假设，进一步阐明湍流和推移质输运之间的相互作用，并提供预测河段尺度泥沙通量的理论和经验模型。这些模型将在当地和国际实地进行测试，并将通过提供对陡峭溪流中泥沙通量的准确和机械估计，改变对景观演变和河流恢复设计的预测。这项研究的学术价值是对控制陡峭溪流中的湍流和泥沙输送的过程有一个基本的和预测性的理解。泥沙输送和河流恢复的框架将被用来教育研究生、本科生和K-12年级的学生关于水资源和正常运行的河流生态系统的重要性。提出了四个教育目标：1)一系列培养批判性思维、科学写作和跨学科团队技能的研究生课程，2)本科生和研究生的国际研究经验，3)教育K-12学生河流过程的计划，以及4)鼓励年轻女性进入数学、科学和工程职业的新的女性科学营。

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.