HR: 1330h
AN: H52A-1149    [PDF]
TI: Three-Dimensional Hydraulics of Pool-Riffle Sequences in Low-Gradient Streams
AU: * Rodriguez, J F
EM: jose.rodriguez@newcastle.edu.au
AF: School of Engineering, The University of Newcastle, University Drive, Callaghan, NSW 2308 Australia
AU: Garcia, M H
EM: mhgarcia@uiuc.edu
AF: V. T. Chow Hydrosystems Lab., Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign 205 North Mathews Ave, Urbana, IL 61801 United States
AU: Lopez, F M
EM: flopez@uiuc.edu
AF: V. T. Chow Hydrosystems Lab., Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign 205 North Mathews Ave, Urbana, IL 61801 United States
AU: Garcia, C M
EM: cgarcia2@uiuc.edu
AF: V. T. Chow Hydrosystems Lab., Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign 205 North Mathews Ave, Urbana, IL 61801 United States
AB: Geomorphologists have long recognized the importance of pools and riffles in the development and maintenance of straight, meandering and braided streams. The ecological importance of pools and riffles has also been acknowledged, with the associated hydraulic variability contributing to the habitat richness required for the development of a healthy ecosystem. Most of the pool-riffle studies to date have concentrated on one or two-dimensions only, sometimes using qualitative information on general flow patterns. Several of these studies have recognized that three-dimensional flow patterns are fundamental to the development and maintenance of pools and riffles and have called for a detailed three-dimensional hydraulic characterization. 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), centred pools and riffles (CPR), and alternate pools and riffles (APR). The CPR configuration was included since centred 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.
DE: 1800 HYDROLOGY
DE: 1803 Anthropogenic effects
DE: 1824 Geomorphology (1625)
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting