Need Hydrology help (channel & Flood Calcs)

[planit]

I am new at all this hydrology stuff and need some help.

I have cross sections of a channel at 50' intervals for 400'. I need to calculate where the water level will be at each section with a 1000 CFS running through it. I can't seem to find a direct answer in any books I have looked in. My assumption is that the cross-sectional area of the channel will have something to do with the equation, but I can't seem to find any equations refering to a cross sectional area. Can anyone help me with an equation for this problem?

 

[Bayou]

You can download HEC-RAS from the Corps web site

http://www.hec.usace.army.mil/

It is the standard for one-dimensional backwater calculation programs.

If you want to do the calculations by hand--the equation is the standard step equations which is based on the energy equation. For non-uniform cross-sections this can be a little tricky. RAS is probably the best route, especially since it is free and national accepted.

If your cross-sections are uniform you can just use the Mannings equation.

 

[cvg]

assuming steady, uniform flow with no up or downstream changes in cross section or discharge (big assumption), you could use the mannings equation to get an approximate depth of flow. It is very well documented in Brater and Kings book "Handbook of Hydraulics". Otherwise, Bayou is correct, you must do a backwater calculation.

Chuck
cgopperton@stantec.com

http://www.stantec.com/