Abstract
This technical note examines vegetation effects on hydraulic resistance in small streams and suggests simple quantitative relationships for predicting and quantifying these effects using the plant characteristics with the greatest explanatory power. In particular, we examine the effects of aquatic plant biomass, stature, and architecture on hydraulic performance of five New Zealand streams representing a wide range of channel dimensions, flows, aquatic plant species, and assemblages. Comparisons among the vegetation parameters indicated that ratios of the site-averaged canopy height to the mean flow depth and of the site-averaged plant length to the mean flow depth were the best roughness descriptors. Effects of individual plant species and their characteristic patch patterns were not significant. The data from all sites collapsed around single lines, suggesting that general physical parameters of vegetation should be the primary determinants of hydraulic resistance in streams studied, not species-specific parameters, as often assumed.
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Acknowledgments
This study was partly funded by the Foundation for Research Science and Technology (New Zealand, Contract No. UNSPECIFIEDCO1X0308), the Christchurch City Council (CCC), and the University of Aberdeen, Scotland. The writers are grateful to CCC staff members O. Southen and K. McCombs for help with site selection and technical and logistical support. D. Sutherland and J. Sykes helped with field measurements and laboratory analyses of plant samples. R. Spigel and G. Smart provided useful suggestions and comments on earlier drafts. The associate editor, H. Nepf, and two anonymous reviewers provided insightful and helpful comments which have been gratefully incorporated into the technical note.
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Information
Published In
Journal of Hydraulic Engineering
Volume 134 • Issue 9 • September 2008
Pages: 1326 - 1332
Copyright
© 2008 ASCE.
History
Received: Jan 9, 2006
Accepted: Feb 27, 2008
Published online: Sep 1, 2008
Published in print: Sep 2008
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