Fluvial Dynamics of Cutoffs and Abandoned Channel Development on Meandering Rivers

这个项目将促进对曲折河流截流机制的理解，这是一种无处不在但却鲜为人知的河流特征。蜿蜒的河流是地球表面最容易辨认的地貌之一，它们复杂的空间格局长期以来一直引起地理学家和其他地球科学家的兴趣。曲折河流的一个特征是形成断流，弯曲的河道彼此之间移动得足够近，以便在紧弯的内部或颈部形成一条新的河道。截流的发展通常会产生牛弓湖，因为弯道出入口发生沉积，河流沿着新的截流河道的路径前进，通过废弃弯道的水流停止。尽管过去有大量关于曲折河流的工作，但对弯道截流形成的机制的了解还不完整。因此，对曲折河流的时空动态进行准确建模和预测的能力有限。针对这一研究需要，本项目将研究截流河道启动后的演变、水流结构的形态及其对淤积和侵蚀形态的影响，以及截流后主槽水流结构和沉积和侵蚀形态的变化。为了解决这些问题，研究人员将使用最先进的现场测量技术，以高分辨率捕捉瓦巴什河沿伊利诺伊州-印第安纳州边界不断演变的截流处的三维水流结构以及侵蚀和沉积模式是如何相互作用的，沃巴什河就在瓦巴什河和俄亥俄河汇合处的上游。他们还将在弯道截流的物理模型中进行一系列的实验室实验，以检查各种截流构型下的三维流动结构、河床形态和渠道变化。最后，他们将开发数值模型来模拟截流动态，使用现场和实验室数据来调节和验证计算模型。经过验证和充分测试的模型将为在更大范围的边界条件下预测曲折河流的截流动态提供先进的理论工具。该项目将增进对曲折河流发展过程的基本理论理解，并为提高曲折河流动态行为建模的预测能力奠定基础。该项目还将产生与河流管理有关的实用知识，包括与可能阻碍商业航行的截流有关的沉积问题，保护截流和牛尾湖遗址的河岸生境，以及河流恢复活动，包括维持或建立牛尾湖与主要河道之间的连通，特别是在河流已改道的地方。该项目将有助于伊利诺伊大学香槟分校研究生和本科生的跨学科培训(将研究成果纳入课程)。它还将在一年一度的伊利诺伊州科学奥林匹克竞赛和将于2014年由伊利诺伊州主办的国家科学奥林匹克竞赛上，让高中生，包括来自代表人数不足的群体的学生，接触到推动理论并服务于社会的尖端科学研究。

This project will advance the understanding of the mechanics of meandering river cutoffs, a ubiquitous, yet poorly understood feature of rivers. Meandering rivers are among the most recognizable landforms on the earth's surface, and their complex spatial patterns have been of interest to geographers and other earth scientists for a long time. A characteristic feature of meandering rivers is the development of cutoffs, where curved channels migrate close enough to one another for a new channel to developt across the interior portion, or neck, of a tight bend. The development of cutoffs typically produces oxbow lakes as sedimentation occurs at the bend entrance and exit, the river follows the path of the new cutoff channel, and flow through the abandoned bend ceases. Despite an abundance of past work on meandering rivers, knowledge of the mechanisms by which bend cutoffs develop is incomplete. As a consequence, the capacity to accurately model and predict the spatial and temporal dynamics of meandering rivers is limited. In response to this research need, this project will address questions concerning cutoff channel evolution after they have been initiated, the patterns of the flow structures and how these impact sedimentation and erosion patterns, and how flow structures in the main channel as well as sedimentation and erosion patterns change after the cutoff has been initiated. To address these questions, the investigators will use state-of-the-art field measurement techniques to capture, at a high resolution, how three-dimensional flow structure and patterns of erosion and deposition interact at an evolving cutoff of the Wabash River along the Illinois-Indiana border just upstream from the confluence of the Wabash and Ohio rivers. They also will conduct a series of laboratory experiments in a physical model of a bend cutoff to examine three-dimensional flow structure, bed morphology, and channel change for a variety of cutoff configurations. Finally, they will develop numerical models to simulate cutoff dynamics, using field and laboratory data to condition and validate the computational models. The validated and fully tested models will then provide an advanced theoretical tool for predicting cutoff dynamics along meandering rivers over an extended range of boundary conditions. This project will enhance knowledge about meandering rivers by contributing to basic theoretical understanding of the processes involved in the development of bend cutoffs and by providing the basis for improved predictive capabilities for modeling the dynamic behavior of meandering rivers. The project also will yield practical knowledge relevant to river management, including sedimentation problems associated with cutoffs that can impede commercial navigation, the conservation of riparian habitat at the sites of cutoffs and oxbow lakes, and river restoration activities that include maintaining or establishing connectivity between oxbow lakes and the main river channel, especially where rivers have been channelized. The project will contribute to interdisciplinary training for graduate and undergraduate students at the University of Illinois at Urbana-Champaign (by incorporating findings into courses. It will also expose high school students, including students from underrepresented groups, to cutting-edge scientific research that advances theory and serves society at the annual Illinois Science Olympiad and at the National Science Olympiad, which will hosted by the state of Illinois in 2014.