headwater calcs

[dgcwater]

What is the best method to use in calculating headwater elevations? What computer programs are recommended? How do hydraulic grade lines coincide with headwater elevations? If I have a pipe system a few hundred feet long, and I want to know what headwater elevation I have at the upstream open end, will the hydraulic grade lines reflect this?

 

[froude]

I think there are a lot of computer programs that will compute HGL info. The recent thread "How Do YOU Design Storm Drain" contains alot of this info. Some software includes StormCAD, HydroCAD, EPA-SWMM, etc.

You can probably start your HGL calculations at the downstream end of your system based on a variety of boundary conditions (known starting WSEL, pipe crown, rating curve, etc.) and work your way upstream, incorporating headlosses due to friction and junctions. Ultimately, you will have some loss associated with your inlet (be it a headwall, drop inlet, etc.) and you should be able to calculate your upstream headwater elevation.

 

[Ryb01]

Before attempting to use software to determine the headwater and hydraulic gradeline elevations it's important to understand how the calculations are performed. This knowledge is required for key input paramaeters (i.e friction loss coefficients, tailwater ,inlet paramters, etc)

A good starting reference is the HEC-22:Urban Drainage Design Manual. As froude has said there's been some recent discussion on "How do you design and storm drain" and also several other threads regarding hydraulic grade line which may be useful for additional reference.