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# Critical Depth of Open-Channel Flow

For a given value of specific energy, the critical depth gives the greatest discharge, or conversely, for a given discharge, the specific energy is a minimum for the critical depth.

For rectangular channels, the critical depth, dc ft (m), is given by

dc =[Q2/b2g]1/3

where
dc =critical depth, ft (m)

Q= quantity of flow or discharge, ft3/s (m3/s)

B= width of channel, ft (m)

### Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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## 10 comments on "Critical Depth of Open-Channel Flow"

Ravi says:

Hi,
It is good………

Peppernspice says:

this is what i’ve been looking for..
simple and straightforward!
thanks

mazetas says:

that was short and sharp

Flash says:

What does q equal if its a wide channel ?

Conor says:

q = Q/b ; (m³s-1/m)
b = the channel width ; (m)
Q = flow rate ; (m3/s)

Tamrat says:

The concept of critical depth for engineer is like you wrote here. That is great way. But the meaning critical depth is that water molucule upstream and downstream of the critical depth wont comunicate. It is a point of discontinity.

Eng. Sayed Rasekh says:

if we introduce more formula for tripoziod channel it would be useful

bhanumathy says:

thaks this is what iam searching for..

Komal SHARMA says:

The specific energy of triangle channel for critical depth

david says:

If water is pouring out of an horizontal canal into the void, the depth at the last section (before pouring) is the critical depth