If r is the normal depth of scour by Lacey equation, the depths below HFl up to which the upstream and downstream sheet piles in a weir are usually preferred to protect against the effect of scour are respectively
1
2.0 R and 1.5 R
2
1.0 R and 1.25 R
3
2.5 R and 1.25 R
4
1.5 R and 2.0 R
5
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