SGER: Fluvial Dynamics of a Large-River Meander Cutoff

SGER：大河曲流截断的河流动力学

• 批准号: 0852865
• 负责人: Bruce Rhoads
• 金额: $ 6.5万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-01-01 至 2011-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0852865&HistoricalAwards=false
• 关键词: SGER; Fluvial; Dynamics; Large; River

Meandering is a fundamental characteristic of many natural rivers that has yet to be adequately explained. The dynamics of meanders involves the continuous evolutionary development of sequences of meander bends through time as the channel migrates laterally and downstream. Individual bends can evolve into complex forms characterized by multiple arcs of curvature, with these loops evolving to curve back upon themselves at their entrance and exit to form a narrow neck. Flow across the neck during floods eventually leads to the development of a new channel at this location, a process known as a meander cutoff. The old meander loop is then abandoned by the flowing river as sediment plugs the entrance and exit of the loop to form an oxbow lake. Recent research has emphasized the importance of meander cutoffs in the dynamics of meander trains, or sequences of bends. Cutoffs can have a substantial influence on bend interactions, because these events often trigger new patterns of evolutionary development of bends adjacent to the cutoff, which in turn affect other bends throughout a meander sequence. This Small Grant for Exploratory Research will examine the development of a new meander cutoff along the lower reach of the Wabash River on the Illinois-Indiana border. The investigators have been monitoring the new cutoff since the days after it formed in June 2008, and they will use funds from this award to continue to monitor its development and to examine the influence of the cutoff on the dynamics of a large-river confluence immediately downstream where the Wabash flows into the Ohio River. The investigators will focus on how the cutoff affects the three-dimensional flow structure of the river at the upstream and downstream ends of the cutoff channel, the developing flow structure within the cutoff channel and within the meander loop that is being cutoff, and the dynamics at the confluence immediately downstream. They will relate documented patterns of flow structure to patterns of channel erosion and deposition to establish linkages between fluvial processes and fluvial forms within the evolving cutoff. This will be done by (1) mapping the extant morphology of the cutoff channel, the bed morphology of the meander loop, and analyzing ancillary information on the occurrence of the cutoff and its influence on the Wabash River-Ohio River confluence; (2) measuring patterns of three-dimensional flow structure at the upstream and downstream ends of the cutoff, within the cutoff channel and within the meander loop during events of different flow stages; (3) mapping patterns of erosion and deposition at the upstream and downstream ends of the cutoff, within the cutoff channel, and within the meander loop; and (4) measuring the flow structure and mapping patterns of sedimentation at the Wabash-Ohio confluence.This research project will make a substantial field-based contribution to the understanding of the dynamics of meander cutoffs, which can later inform development of general process-based numerical models of meandering. The project also will enhance basic understanding of the ways that the formation of the cutoff affects the changing dynamics of the large Wabash-Ohio river confluence immediately downstream. The project will have positive broader impacts by providing research and training opportunities for graduate and undergraduate students and for providing valuable data to enable local government agencies and other stakeholders to determine how to deal with the land-management implications of the new cutoff and related changes.

蜿蜒是许多天然河流的基本特征，但尚未得到充分解释。 曲流的动力学涉及随着河道横向和下游迁移，曲流弯曲序列随着时间的推移不断进化发展。 单个弯曲可以演变成以多个曲率弧为特征的复杂形式，这些环演变成在其入口和出口处向后弯曲以形成狭窄的颈部。 洪水期间流过颈部的水流最终会导致该位置形成新的河道，这一过程称为曲流截断。 然后，由于沉积物堵塞了环路的入口和出口，形成了牛轭湖，旧的曲流环路被流动的河流抛弃了。 最近的研究强调了曲折截止在曲折列车或弯曲序列动力学中的重要性。 截止点可能会对弯曲相互作用产生重大影响，因为这些事件通常会触发截止点附近弯曲的进化发展的新模式，进而影响整个曲流序列中的其他弯曲。 这笔探索性研究的小额赠款将研究伊利诺伊州和印第安纳州边界沃巴什河下游的新曲流截流区的开发情况。 自2008年6月新截流形成以来，调查人员一直在监测新截流，他们将利用该奖项的资金继续监测其发展，并立即研究截流对大河汇流动态的影响。沃巴什河流入俄亥俄河的下游。 研究人员将重点研究截流如何影响截流河道上下游端河流的三维水流结构、截流河道内和被截流的曲流环路内发展的水流结构以及动态。在紧邻下游的汇合处。 他们将记录的水流结构模式与河道侵蚀和沉积模式联系起来，以在不断变化的截流范围内建立河流过程和河流形式之间的联系。 这将通过以下方式完成：（1）绘制截流河道的现存形态、曲流环路的河床形态，并分析截流发生及其对沃巴什河-俄亥俄河汇流处影响的辅助信息； (2)测量不同水流阶段事件中截流上下游端、截流河道内以及曲流环路内的三维流结构模式； (3) 绘制截流区上游和下游端、截流河道内以及曲流环路内的侵蚀和沉积模式； (4) 测量沃巴什-俄亥俄州交汇处的流动结构和沉积模式。该研究项目将为理解曲流截断的动力学做出重大的实地贡献，这可以为以后一般过程的发展提供信息。基于曲流的数值模型。 该项目还将增强对截断形成如何影响紧邻下游的大型沃巴什-俄亥俄河交汇处动态变化的方式的基本了解。 该项目将为研究生和本科生提供研究和培训机会，并提供有价值的数据，使地方政府机构和其他利益相关者能够确定如何处理新的停产和相关变化对土地管理的影响，从而产生更广泛的积极影响。