For the design of cross drainage works, the waterway of the drain is determined using Lacey's equation given by (Here: P is the wetted perimeter in meters and Q is the total discharge in cumecs.)
(Symbols and notations carry their usual meaning)
1
P = 4.75Q2
2
P = 1.5\(\sqrt{Q} \)
3
P = 1.5Q2
4
P = 4.75\(\sqrt{Q} \)