The normal depth in a wide rectangular channel is increased

The normal depth in a wide rectangular channel is increased by 10%. The percentage increase in the discharge in the channel is

The discharge in the channel is given by

Q =	1	AR^2/3S^1/2
	n

⇒ Q =	1	(By)		By		^2/3	S^1/2
	n			B + 2y

For a wide rectangular channel
B >> y

∴ Q =	1	(By)(y)^2/3S^1/2
	n

∴ Q ∝ y^5/3
Let Q₁ = k(y)^5/3
∴ Q₂ = k(1.1y)^5/3

∴	Q₂ − Q₁	× 100
	Q₁

=	(1.1y)^5/3 − (y)^5/3	× 100 = 17.21%
	(y)^5/3