Doctoral Dissertation Research: Flow Dynamics and Channel Morphology at Natural Confluent-Meander Bends

河流汇流的几何形状是影响水流结构、泥沙输移和河床形态的控制因素。 以前的实验和理论模型的汇合动力学的一个基本假设是，收敛的河流有直通道角配置。 然而，天然河道，特别是蜿蜒河流的河道，会弯曲和弯曲。 这一属性导致了这样的假设，即自然河流和河流汇流优先发生在弯曲弯曲的凹外银行。 由此产生的汇合，被称为汇合曲流弯曲，观察到超过世纪前，但很少受到科学的关注。 本博士论文研究项目的目标是通过对自然汇流曲流弯道进行实地调查，来促进对这一可能常见汇流的水流结构和形态的理解。 通过地图和数字正交四边形解释，将产生一个系统的汇流清单，以确定汇流曲流弯曲的规律性。 在伊利诺斯州中东部和印第安纳州中西部不同大小和不同几何特征的汇流曲流弯曲处收集的现场数据将包括测量时间平均三维速度分量以辨别水流结构，调查河床和河道形态以记录地貌变化，记录水温和电导率以揭示汇流流之间混合的空间模式。 将收集一系列流动条件的数据，以记录动量通量变化对流动结构和通道形态的影响。 历史航空照片也将被解释，以确定研究地点的汇流曲流弯曲代表一个准稳定的渠道配置在蜿蜒的排水network.The研究结果将揭示在汇流曲流弯曲的流量和地貌结构的特点，提供管理决策的基础和汇流和曲流弯曲动力学的基础知识的贡献。 这种复杂的水动力环境对工程师在评估渠道设计标准和通过排水网络的洪水路由时，以及对关注污染物扩散和水质的水资源管理人员具有实际影响。 汇流处的水流结构和地貌变化也提供了破坏栖息地的当地多样性。 地貌学和生态学之间的功能关系越来越相关，为河流生态学家提供更好的栖息地评估。 这些河流和形态的考虑，使知识的流动动力学和泥沙输运在这个可能常见的，但迄今为止被忽视，汇合。 科学和渠道管理决策的关键。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。

The geometry of river confluences is a controlling factor that influences flow structure, sediment transport and bed morphology at channel junctions. An underlying assumption of previous experimental and theoretical models of confluence dynamics has been that converging rivers have straight channels with angular configurations. However, natural channels, particularly those of meandering rivers, curve and bend. This property has led to the hypothesis that natural stream and river confluences preferentially occur on the concave outer bank of meander bends. The resulting confluence, referred to as a confluent-meander bend, was observed over a century ago but has received little scientific attention. The goal of this doctoral dissertation research project is to advance the understanding of the flow structure and morphology of this possibly common confluence by conducting a field investigation of natural confluent-meander bends. A systematic inventory of confluences throughout selected watersheds will be generated from map and digital ortho-quadrangle interpretation to determine the regularity of confluent-meander bends. Field data collection at confluent-meander bends of varying size and with differing geometric characteristics in east-central Illinois and west-central Indiana will include measuring time-averaged three-dimensional velocity components to discern flow structure, surveying bed and channel morphology to document geomorphic change and recording water temperature and conductivity to reveal spatial patterns of mixing between the confluent flows. Data for a range of flow conditions will be collected to document the effects that variation in momentum flux has on flow structure and channel morphology. Historical aerial photographs will also be interpreted to determine if the confluent-meander bends of the study sites represent a quasi-stable channel configuration in meandering drainage networks.The results of this study will reveal the characteristics of flow and geomorphic structures at confluent-meander bends to provide a basis for management decisions and a contribution to basic knowledge of confluence and meander bend dynamics. This complex hydrodynamic environment has practical ramifications for engineers when assessing channel design criteria and flood routing through drainage networks, as well as for water resource managers concerned about pollutant dispersal and water quality. Flow structure and geomorphic variability at confluences also provide local diversity that disrupts habitat. Functional relations between geomorphology and ecology are increasingly relevant to providing a better assessment of habitat for riverine ecologists. These fluvial and morphological considerations make knowledge of flow dynamics and sediment transport at this possibly common, yet heretofore overlooked, confluence. essential for science and channel management decisions. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.