aalto1 untyped-item.component.html
Flow resistance in environmental channels : focus on vegetation
Loading...
URL
Journal Title
Journal ISSN
Volume Title
Doctoral thesis (article-based)
Electronic archive copy is available via Aalto Thesis Database.
Checking the digitized thesis and permission for publishing
Instructions for the author
Instructions for the author
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Authors
Date
Major/Subject
Mcode
Degree programme
Language
en
Pages
54, [66]
Series
Helsinki University of Technology Water Resources publications, Teknillisen korkeakoulun vesitalouden ja vesirakennuksen julkaisuja, 10
Abstract
This thesis aims to improve the reliability of the determination of flow resistance in environmentally acceptable channels and floodplains. Special emphasis was placed on addressing the hydraulic effects of vegetation. For this reason, laboratory flume studies with living vegetation were employed. The most notable finding was that, when compared to leafless conditions, the presence of leaves increased the friction factor up to seven-fold. This was strongly dependent on the flow velocity. In addition, the linkage between flow resistance, channel properties, and physical habitat was investigated. For this purpose, field studies were conducted in degraded, restored, and natural channel reaches.
To determine friction factor f or Manning's n for non-submerged woody vegetation, a new procedure based on the measurable characteristics of vegetation and flow was developed. A major advantage of this procedure over the old methods was its ability to estimate the flow resistance of woody vegetation in both leafless and leafy conditions. In determining the velocity profile and flow resistance caused by submerged flexible vegetation, the approach developed by Stephan (2002) was found to be suitable. However, a new formulation was proposed for the shear velocity based on deflected plant height. This modification offered better practical applicability than the original formulation, which requires complicated turbulence measurements.
In the field studies, the experimental results for friction factors were, excluding those for low flows, in agreement with the values presented in the literature. Overall, the gathered field data from degraded, restored, and natural channel reaches formed a reference data set, which could be useful in other similar restoration or engineering projects. The field studies showed that both flow resistance and cross-sectional geometry were vital factors in determining local hydraulic conditions. The parameters defining these two factors were found to be simple but nonetheless valuable in evaluating the success of a project which aims to restore local hydraulics. A new procedure for applying the success criteria in the post-project evaluation of local hydraulics was developed.
Description
Keywords
Other note
Parts
- Järvelä J., 2002. Flow resistance of flexible and stiff vegetation: a flume study with natural plants. Journal of Hydrology 269, numbers 1-2, pages 44-54. [article1.pdf] © 2002 Elsevier Science. By permission.
- Järvelä J., 2002. Determination of flow resistance of vegetated channel banks and floodplains. In: Bousmar D. and Zech Y. (editors), River Flow 2002. Lisse, Swets & Zeitlinger, pages 311-318. [article2.pdf] © 2002 Swets & Zeitlinger. By permission.
- Järvelä J., 2003. Influence of vegetation on flow structure in floodplains and wetlands. In: Sánchez-Arcilla A. and Bateman A. (editors), Proceedings of the 3rd IAHR Symposium on River, Coastal and Estuarine Morphodynamics (RCEM 2003). Madrid, IAHR, pages 845-856. [article3.pdf] © 2003 International Association of Hydraulic Engineering and Research (IAHR). By permission.
- Järvelä J., 2004. Determination of flow resistance caused by non-submerged woody vegetation. International Journal of River Basin Management 2, number 1, pages 61-70. [article4.pdf] © 2004 International Association of Hydraulic Engineering and Research (IAHR). By permission.
- Järvelä J. and Helmiö T., 2004. Hydraulic considerations in restoring boreal streams. Nordic Hydrology 35, number 3, in press. [article5.pdf] © 2004 by authors and © 2004 IWA Publishing. By permission.
- Helmiö T. and Järvelä J., 2004. Hydraulic aspects of environmental flood management in boreal conditions. Boreal Environment Research 9, in press. [article6.pdf] © 2004 Boreal Environment Research. By permission.