Doctoral Dissertation Research: The Three-Dimensional Bed and Flow Structure of Pool-Riffle Sequences in the Embarras River

浅滩与深滩交替，或小河与水池交替，是许多冲积河流的共同特征。池沟结构影响河流曲流动力学，并为河流生境提供形态和水力多样性。本博士论文研究项目将进一步加深对池-膛线序列三维动力学的认识。该项目将通过对伊利诺伊州中东部的一条小的、低坡度的、砾石床的农业河流——奥格兰斯河的一段河段的案例研究，重点关注池水形式和动态的不同方面。将开展的活动包括开发一种三维形态指数，根据河道形态的下游和横流不对称以及河纹波峰和池槽之间的总垂直差等参数来定义水池和河纹。该项目将探索上游河槽、下游水池和点坝的相关序列，以检验将这些水池和河槽作为引发蜿蜒的重要因素的假设。该项目还将包括直接比较流体通过各种池-膛线类型的运动模式。流体流速测量将用于估计近床剪切应力测量的模式，并将这些模式与通过池纹序列的沉积物运输联系起来。本研究采用的方法包括水道形态测量、三维水流结构和泥沙运移测量以及河床物质的结构分析。研究结果将产生关于池和膛线的三维形态和动力学的基本知识。这些知识将推进关于河道形态和动态的基础理论。这对于河流自然化的设计标准的发展也将是重要的，这是一种河流管理，旨在建立形态和水力多样化，动态稳定的河流渠道，能够支持健康的，生物多样化的水生生态系统。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研究生涯。

Alternating shallows and deeps, or riffles and pools, are common features in many alluvial rivers. Pool-riffle structures affect the dynamics of river meandering, and they provide morphological and hydraulic diversity for stream habitat. This doctoral dissertation research project will further the understanding of the three-dimensional dynamics of pool-riffle sequences. The project will focus on different aspects of pool-riffle form and dynamics through a case study in a reach of the Embarras River, a small, low-gradient, gravel-bed agricultural stream in east central Illinois. Among the activities to be undertaken are the development of a 3-D form index that defines pools and riffles based on parameters the include downstream and cross-stream asymmetry of channel morphology and the total vertical difference between riffle crests and pool troughs. The project will explore related sequences of upstream riffles and downstream pools and point bars in order to test hypotheses that associate these kinds of pools and riffles as important elements that initiate meandering. The project also will include direct comparisons of the patterns of fluid motion through a variety of pool-riffle types. Fluid-flow velocity measurements will be used to estimate patterns of near-bed shear stress measurements and relate these patterns to sediment transport through pool-riffle sequences. The methods employed in this study will include surveying of channel form, measurements of three-dimensional flow structure and sediment transport, and textural analysis of bed material.Results of the research will yield basic knowledge on the three-dimensional form and dynamics of pools and riffles. Such knowledge will advance basic theory on stream channel form and dynamics. It also will be important for the development of design criteria for stream naturalization, a type of stream management that seeks to establish morphologically and hydraulically diverse, dynamically stable stream channels that are capable of supporting healthy, biologically diverse aquatic ecosystems. 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.