EAR-PF: Quantifying the effects of flow transience on sediment transport

科林·菲利普斯博士被授予美国国家科学基金会地球科学博士后奖学金，在明尼苏达大学开展研究和教育推广计划。他将研究砾石在瞬态和间歇水浸下的运移过程。砾石河代表了山脉切割的速率限制步骤，也为许多水生物种提供了重要的栖息地和繁殖地。这些实验将为了解气候和土地利用的潜在变化如何影响砾石流奠定基础。此外，这些实验将为河流管理者调节水坝下的流量和河流恢复项目提供定量框架。这些实验的结果将转化为溪流恢复从业者的交互式在线工具。此外，从该项目中获得的知识将通过国家地球表面动力学中心2 （NCED2）暑期研究所的课程和实验传递给年轻科学家，并通过与NCED2 REU学生的合作传递给未来的年轻科学家。我们对砂砾河动力学的大部分理解来自恒定或缓慢变化的洪水下的水槽实验。许多在稳定水流条件下发展起来的理论，在多次洪水的平均条件下，对砾石河的动力学提供了合理的预测，然而，由于泥沙运输的随机性，这些预测是否会因水流不稳定或颗粒现象而失效仍不清楚。通过使用实验室实验，他将测试洪水形状和顺序的相对重要性，以确定非定常流如何驱动沉积物运输。该项目将通过跟踪几组标记颗粒，在不同大小和持续时间的各种单一和序列流动下，比较颗粒水平上的砾石运输动力学，但脉冲是等效的（超过颗粒运动阈值的时间积分动量）。

Dr. Colin Phillips has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out a research and educational outreach plan at the University of Minnesota. He will investigate the process of gravel transport in response to transient and intermittent flooding. Gravel rivers represent the rate limiting step in the incision of mountains and also provide critical habitat and breeding grounds to numerous aquatic species. These experiments will form the basis for understanding how potential changes in climate and land use will affect gravel streams. In addition these experiments will provide a quantitative framework for stream managers regulating flow releases below dams and stream restoration projects. The results from these experiments will be turned into interactive online tools for stream restoration practitioners. Furthermore, the knowledge gained from this project will be transferred to young scientists through classes and experiments during the National Center for Earth Surface Dynamics 2 (NCED2) Summer Institute, and to future young scientists by collaborating with NCED2 REU students.A large majority of our understanding of gravel river dynamics comes from flume experiments under constant or slowly varying floods. Many of the theories developed under steady flow provide reasonable predictions of the dynamics of gravel rivers when averaged over numerous floods, however due to the stochastic nature of sediment transport it remains unclear whether these predictions break down due to flow unsteadiness or granular phenomena. Through the use of laboratory experiments he will test the relative importance of flood shape and sequence to determine how an unsteady flow drives sediment transport. This project will compare the dynamics of gravel transport at the particle level through the tracking of several populations of marked particles under a variety of single and sequences of flows of varying magnitude and duration, but equivalent impulse (time-integrated momentum above the threshold of particle motion).