Flow around a bend results in a rise of water surface on the outside of the bend and it is natural to consider that extra height of channel wall on the outside of bend to prevent overflow of water.
However, for supercritical flow in channel, owing to the effect of superelevation extra height of channel wall should be provided on both sides of the bend. This is because supercritical flow around a bend would make water level go up alternatively on the outside and inside of the bend owing to cross waves. This cross wave pattern may continue for some distance downstream. As such, both sides of bend shall be lengthened to cater for this effect.
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This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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