Question

What will be the carrying capacity of a horizontal rectangular channel 4 m wide, conveying a discharge of 1 cumecs per meter width of channel?
1. 1.000 m³/s
2. 2.085 m3/s
3. 4.000 m3/s
4. 8.000 m3/s

Answer 1

Correct Answer - Option 3 : 4.000 m3/s

Concept:

Rectangular Channel Section:

A rectangular channel section is the most economical when either the depth of flow is equal to half the bottom width or the hydraulic radius is equal to half the depth of flow.

Trapezoidal Section:

A trapezoidal section is the most economical if half the top width is equal to one of the sloping sides of the channel or the hydraulic radius is equal to half the depth of flow.

Triangular Channel Section:

A triangular channel section is the most economical when each of its sloping sides makes an angle of 45^o with vertical or is half square described on a diagonal and having equal sloping sides.

Calculation:

The carrying capacity of a horizontal rectangular channel is

= Conveying a discharge per meter width × Width of the rectangular channel

= 1 cumecs per meter width × 4 m = 4.000 m³/s