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

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

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.