Concept of Bed Roughness Boundary Layer and Its Application to Bed Load Transport in Flow with Non-Submerged Vegetation

Ho-Seong Jeon, Makiko Obana, Tetsuro Tsujimoto

Department of Civil Engineering, Nagoya University, Nagoya, Japan.

DOI: 10.4236/jwarp.2014.610082                

Abstract

Ecosystem conservation has become one of the purposes in river management as well as flood mitigation and water resources management, and understanding of river flow and morphology in a stream with vegetation becomes important. Recently 2D depth averaged analysis is familiar even in a stream with vegetation by taking account of form drag due to vegetation. However, the shear stress in vegetated area is not properly described because the resistance law due to bed roughness is not reasonably modified in vegetated area. In this study, we discussed the bed roughness boundary layer in flow with non-submerged vegetation to deduce a reasonable relation between U and u* in vegetated area toward improving the analysis of sediment transport. The results show that the modification of resistance law using by thickness, velocity distribution in that layer was found to bring significant improvement of accurate estimation of shear velocity and subsequently the sediment transport. The proposed modification is improved by 2D depth averaged analysis based on this concept, and its application is certificated through flume experiment.

Keywords

Flow with Non-Submerged Vegetation, Boundary Layer, Bed Roughness, Bed Load Transport

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Tsujimoto, T. (2010) Structure and Functions of River Ecosystem—Approach from Ecohydraulics. Proceedings of 10th International Symposium on Ecohydraulics, Invited Lecture, IAHR, Seoul, CD-ROM.
[2]	Tsujimoto, T. (1999) Flow and Fluvial Processes in Streams with Vegetation. Journal of Hydraulic Research, 37, 789-803. http://dx.doi.org/10.1080/00221689909498512
[3]	Liu, D., Diplas, P., Fairbanks, J. and Hodges, C. (2008) An Experimental Study of Flow through Rigid Vegetation, Journal of Geophysical Research, 113, Article ID: F04015.
[4]	Obana, M, Uchida, T. and Tsujimoto, T. (2012) Deposition of Sand and Particulate Organic Matter in Riparian Vegetation. Advances in River Engineering, JSCE, 47-52. (in Japanese)
[5]	Ashida, K. and Michiue, M. (1972) Hydraulic Resistance of Flow in an Alluvia Bed and Bed Load Transport Rate. Proceedings of JSCE, No. 206, 59-69. (in Japanese)