Question

A rectangular channel is having depth 2m and width 3m, bed slope of 1 in 700. The value of manning’s roughness co efficient (n) is 0.06, estimate the discharge through the channel

Answer 1

Answer:

Q = 3.42 m³/s

Explanation:

given,

depth of the rectangular channel, y = 2 m

width of the channel, B = 3 m

slope of the channel, = 1 in 700

manning's coefficient, n = 0.06

discharge through the channel

$Q = \dfrac{1}{n}AR^{2/3}\sqrt{S}$

R is the hydraulic radius.

hydraulic radius is the ratio of area of the channel to wetted perimeter.

A = B y = 3 x 2 =6 m²

P = B + 2 y = 3 + 2 x 2 = 7 m

$R = \dfrac{6}{7}= 0.857 m$

now,

$Q = \dfrac{1}{0.06}\times 6 \times 0.857^{2/3}\sqrt{\dfrac{1}{700}}$

  Q = 3.42 m³/s

hence, the discharge through the channel is equal to 3.42 m³/s