Mean Flow and Turbulence Characteristics of Pool -Riffle Structures in Low -Gradient Streams
Rodriguez, Jose Fernando
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https://hdl.handle.net/2142/83222
Description
Title
Mean Flow and Turbulence Characteristics of Pool -Riffle Structures in Low -Gradient Streams
Author(s)
Rodriguez, Jose Fernando
Issue Date
2003
Doctoral Committee Chair(s)
Garcia, Marcelo H.
Department of Study
Civil Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Language
eng
Abstract
Laboratory flume experiments were carried out to investigate the three-dimensional flow structure and turbulence characteristics of pools and riffles. The experiments included three different bed configurations: flat bed (FB), centered pools and riffles (CPR), and alternate pools and riffles (APR). The CPR configuration was included since centered pools minimize the possibility of scour near the banks, and are thus particularly suitable for urban rehabilitation projects where bank erosion is undesirable. The sequence FB-CPR-APR represents not only flows with increased complexity but also steps in the restoration process of a degraded stream. Accordingly, the FB case characterizes the behaviour of the channelized stream with no geomorphological diversity, the CPR experiment describes a rehabilitation alternative with man-made in channel structures, and the APR set is representative of more natural conditions. Each series included low and high flow conditions. Flow velocities were measured using an Acoustic Doppler Velocimeter on a very dense transverse grid at several cross sections. The high resolution of the velocity data (both in time and space) allowed for the identification of patterns of flow convergence and divergence, secondary circulation, wall shear stresses and turbulence, specific of each configuration. Implications for sediment transport, bed and bank morphology and aquatic habitat are discussed. Some of the results presented in this work have been used as a guide for the design, construction and monitoring of artificial pool-riffle sequences in the West Fork of the North Branch of the Chicago River at Northbrook, Illinois.
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