Fluvial Dynamics of Cutoffs and Abandoned Channel Development on Meandering Rivers

曲流河流截流和废弃河道开发的河流动力学

• 批准号: 1125543
• 负责人: Bruce Rhoads
• 金额: $ 16.41万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1125543&HistoricalAwards=false
• 关键词: Fluvial; Dynamics; Cutoffs; Abandoned; Channel

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.

这个项目将促进对蜿蜒河流断流机制的理解，这是一个普遍存在的河流特征，但人们对它知之甚少。蜿蜒的河流是地球表面最容易辨认的地貌之一，其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。曲流河流的一个特征是断裂处的发展，在那里，弯曲的河道彼此迁移得足够近，从而形成一条新的河道，穿过狭窄弯道的内部部分或颈部。由于在弯道入口和出口处发生了沉积，河流沿着新的截流通道的路径流动，并且水流停止流经废弃的弯道，因此截流口的发展通常会产生牛轭湖。尽管过去有大量关于蜿蜒河流的研究，但对弯曲断裂带形成机制的了解尚不完整。因此，准确地模拟和预测曲流河流时空动态的能力是有限的。为响应这一研究需求，本项目将研究切断河道形成后的演变、水流结构模式及其对沉积和侵蚀模式的影响、切断河道形成后主河道的水流结构以及沉积和侵蚀模式的变化等问题。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，以高分辨率捕获三维流动结构和侵蚀和沉积模式，如何在沃巴什河和俄亥俄河汇流处上游沿伊利诺斯州和印第安纳州边界演变的沃巴什河断流处相互作用。他们还将在弯曲截流的物理模型中进行一系列实验室实验，以检查各种截流配置的三维流动结构，床形态和通道变化。最后，他们将开发数值模型来模拟截止动力学，使用现场和实验室数据来调整和验证计算模型。经过验证和充分测试的模型将提供一个先进的理论工具，用于在更大范围的边界条件下预测曲流河流的截止动力学。该项目将有助于对弯曲断口形成过程的基本理论理解，并为改进弯曲河流动态行为建模的预测能力提供基础，从而提高对弯曲河流的认识。该项目还将产生与河流管理相关的实用知识，包括与可能阻碍商业航行的截流有关的沉积问题，截流和牛轭湖遗址的河岸栖息地保护，以及河流恢复活动，包括维持或建立牛轭湖与主河道之间的连通性，特别是在河流已渠化的地方。该项目将通过将研究结果纳入课程，为伊利诺伊大学厄巴纳-香槟分校的研究生和本科生提供跨学科培训。它还将让高中生，包括来自代表性不足群体的学生，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中，接触到前沿的科学研究，这些研究可以促进理论的发展，为社会服务。