https://orcid.org/0000-0002-0288-9611
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Abstract
This technical note presents results from flume experiments conducted in a straight prismatic asymmetric compound channel with two different floodplain roughnesses and rigid emergent vegetation along the floodplain edge in combination with a mobile and fixed main channel bed, respectively. It is found that the contribution of floodplain roughness and vegetation along the floodplain edge to the bulk friction factor is considerably reduced when studied in combination with a mobile main channel bed featuring bedforms. This in turn means that the effect of vegetation along the floodplain edge on the conveyance capacity and bulk friction factor may be overestimated if it is studied solely with fixed bed conditions. The presented results reveal the need to improve our understanding of the complex interplay between mobile beds and vegetation along the floodplain edge and its combined effect on compound channel conveyance capacity and hydraulics.
Acknowledgements
We gratefully acknowledge the technical support of Holger Kroker, Christian David, and Uwe Ecklebe for the experimental set-up and the helpful comments and suggestions of three reviewers and the Associate Editor.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Supplemental data
The power laws fitted to the stage-discharge curves and the full dataset can be accessed via the online version of the technical note.
Supplemental data for this article can be accessed at https://doi.org/10.1080/00221686.2022.2041498.
Notation
| A | = | cross sectional area (m2) |
| d50 | = | median grain size (m) |
| dmin | = | minimum grain size (m) |
| dmax | = | maximum grain size (m) |
| Fmc | = | Froude number in the main channel (–) |
| f | = | Darcy–Weisbach friction factor (–) |
| H | = | water depth (m) |
| Hb | = | bankfull water depth (m) |
| hbf | = | mean bedform height (m) |
| hfp | = | water depth on the floodplain (m) |
| hr | = | relative water depth (–) |
| Q | = | discharge (m3 s−1) |
| Qb | = | bankfull discharge (m3 s−1) |
| Qfp | = | discharge routed via the floodplain (m3 s−1) |
| Qt | = | total discharge (m3 s−1) |
| R | = | hydraulic radius (m) |
| Sfl | = | slope of the compound channel (–) |
| umc | = | mean main channel velocity at the upstream part of the flume (m s−1) |
| x, y, z | = | coordinates (m) |
| σz | = | standard deviation of bed elevation (m) |
| φ | = | porosity (–) |