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

科林·菲利普斯博士获得了美国国家科学基金会地球科学博士后奖学金，将在明尼苏达大学开展一项研究和教育推广计划。他将研究应对瞬时和间歇性洪水的砾石运输过程。砾石河代表着山脉切割中的限速步骤，也为许多水生物种提供了关键的栖息地和繁殖地。这些实验将为理解气候和土地利用的潜在变化将如何影响砾石流奠定基础。此外，这些实验将为河流管理者提供一个量化框架，以调节大坝下的流量释放和溪流恢复项目。这些实验的结果将被转化为溪流恢复从业者的互动在线工具。此外，从这个项目中获得的知识将在国家地球表面动力学2(NCED2)夏季研究所期间通过课堂和实验传递给年轻科学家，并通过与NCED2 REU学生合作传递给未来的年轻科学家。我们对砾石河流动力学的大部分了解来自恒定或缓慢变化的洪水下的水槽实验。在恒定流条件下发展起来的许多理论对砾石河流在多次洪水中平均时的动态提供了合理的预测，然而，由于泥沙运动的随机性质，目前尚不清楚这些预测是由于水流不稳定还是颗粒现象而失效。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，以确定非恒定流如何驱动泥沙运输。该项目将通过跟踪不同数量和持续时间但等效冲量(粒子运动阈值以上的时间积分动量)的各种单一和序列流动下的几个标记颗粒群体，比较颗粒一级碎石运输的动力学。

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).