Journal of the Japan Society of Erosion Control Engineering
Online ISSN : 2187-4654
Print ISSN : 0286-8385
ISSN-L : 0286-8385
Effect of Cross Dpkes for Alternate Bars
Souhei ABEMasayuki WATANABEIwao IZUMIHiroshi IKEYA
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1981 Volume 34 Issue 2 Pages 27-34

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Abstract

Alternate bars are apt to be formed in torrential rivers in alluvial fans and meandering and local scouring due to the bar formation often do damages to channel works.
Control measures against bars which have detrimental effects on channels are studied by means of hydraulic experiments, and cross dykes such as bed girdle and ground sill prove to be effective.
Cross dykes arrangement, footing depth and a height of revetment are discussed taking bars formation mechanisms into consideration.
1) The correlation between Hsmax and ΔHsmax is as follows;
ΔHsmax=0.8 Hsmax
where
Hsmax is the height of alternate bars
and
ΔHsmax is a scouring depth.
2) A height of bars varies in proportion to the interval of cross dykes.
The optimum interval is approximately two (2) times of a channel width in the region on 5≤B/√Q≤10,
where
B is a channel width and Q is a designed discharge.
3) A length and height of bars can be decreased by the use of ground sills.
4) A height of bars and a scouring depth can be decreased by the use of bed girdles in the region of the transition between alternate bars and multiple bars under the condition of L/B=1.5, where L is a interval of bed girdles.

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