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Using HydroCAD to determine conveyance restriction

Using HydroCAD to determine conveyance restriction

Using HydroCAD to determine conveyance restriction

My design firm has been asked by a client of ours to help him with a drainage calculation issue. I am not an engineer, just a CAD designer so I feel a bit over my head here so I just wanted to throw it out to the engineering universe to see if I am stepping in the right direction. We have a 90 acre drainage area going through 2 existing 36" pipes to a ditch, then through 2 more existing 36" pipes to a canal. We are going to connect those two sets of existing pipes with 100 linear feet of 36" HDPE pipes and backfill the ditch. Government agencies are concerned about a negative upstream effect during a 100yr storm event. I guess my main question is can I use HydroCAD to do the calculations to determine if conveyance will be restricted and have a negative upstream impact? Is there anything I should be on the lookout for? Am I in over my head? (Yes)

RE: Using HydroCAD to determine conveyance restriction

Yes, as a CAD designer alone you are not legally qualified to do this work by yourself.

RE: Using HydroCAD to determine conveyance restriction

Yes I am aware of this. But the person I work under is legally qualified to sign off on it if done correctly. So I'm just trying to do as much of the ground work as I can as we are overwhelmed with traditional work as it is.

RE: Using HydroCAD to determine conveyance restriction

No HydroCAD is not industry standard for modeling storm sewer systems requiring HGL/EGL analysis to examine backwater influences. The reviewer will want to see an HGL/EGL analysis for the 100yr event with a fully vetted 100 yr downstream boundary condition per their concerns (tailwater).

RE: Using HydroCAD to determine conveyance restriction

HydroCAD is commonly used for modeling pipe networks and storm sewers as discussed at www.hydrocad.net/sewers.htm

Since you're probably dealing with a small margin-of-error, I would certainly encourage you to cross-check the results against another program.

Peter Smart
HydroCAD Software

RE: Using HydroCAD to determine conveyance restriction

You want to download and read this:


If you can read and understand the material in that PDF you can design what you're trying to design. Whoever stamps the design must also understand that document so he can ethically sign off on the work. Two other (free) software options that might help, once you understand what you're doing:


Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

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