What is considered a "high" flowrate for a waterway? 1

[popos]

Hello all,

I previously posed this in another area, but I quickly found that this area is a better forum for such a question...

Can someone please explain/provide information of what they would consider a low flowrate, a medium flowrate and a high flowrate for a waterway in cfs?

I was told that a creek has a 10 year flow rate of 250 cfs, and I am trying to get an idea of how fast that is in my head as I do not deal with waterflows every day.

thanks to all who respond.

 

[psmart]

It depends entirely on the size of the "waterway". Although "creek" narrows it down a bit, the term means different things in different areas.

You could use Manning's equation to determine the approximate flow rate at any given depth.


Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[cvg]

low medium and high are very subjective, however consider the following:

Columbia River - 400,000 cfs - top width 1,800 feet - 26 ft deep might be considered "large"

Provo River - 1,200 cfs - top width 47 feet - 4 ft deep might be considered medium

your creek is probably considered small

all three might have the same velocity...

 

[froude]

"Low," "medium," and "high" will really just be dependent upon the geometry of your channel. If your question is purely a matter of calculating the velocity, a rough method of obtaining it could be to use the continuity equation (Q = V x A)

where:

Q = flowrate in cu. feet per second
V = velocity in feet per second
A = area in square feet

Realistically, the best way to calculate the velocity would be using Manning's Equation (as PSmart suggested) or, if you don't really care for hand calculations, you can use FlowMaster (by Bentley Systems) or any other simliar software).