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Culvert Design Requirements Help

Culvert Design Requirements Help

Culvert Design Requirements Help

Hello I have been asked to help provide some Civil Engineering Design work, but my main area of experience is Structural. I am at a loss on how to begin or approach this assignment, so any comments/suggestions are appreciated. Here is a list of the task:

For the existing conditions:
-Analyze the existing ditch/culvert capacity for 2 and 100 year flows in terms of hydraulic grade line (HGL)
For proposed conditions:
-Find the Maximum Ponding Elevation (MPE). This is the maximum allowable water surface elevation.
-Calculate the headwater elevation (HW)for the design event (2-yr). It should stay below inlet suffit and existing 2 year HGL.
-Calculate the headwater elevation (HW)for the extreme event (100-yr). It should stay below the MPE and the existing 100 year HGL.

I have a set of plan & profile plans in front of me. As I mentioned previously, my background is primarily structural, so any guidance is appreciated.

RE: Culvert Design Requirements Help

You're being asked to learn an entire field of engineering. This is akin to someone coming to me (a hydrologist) and asking me to provide him a design for a two way reinforced concrete slab on a cantilever. I'd have to go all the way back to college textbooks and reinvent the wheel from there. It's a tall order.

If you're set on delivering, this is pretty comprehensive: (HEC-22)


This is also a good reference if the prior link gets confusing: (NEH 5 and NEH 630)


To help you weed through the material, your main tasks here are as follows:

1) Delineate watersheds on topographic maps
2) Characterize watershed cover, soil cover, and such, to match the runoff hydrology method you've selected (typically Rational or SCS)
3) Characterize rainfall based on location
4) use 1-3 to develop flows
5) characterize pipes and channels based on geometry and roughness, junctions, as explained in HEC-22 (typically via manning's analysis)
6) perform the hydraulics calculations based on steps 4 and 5.

You'll need rainfall data:

You might need soil data, depending on method:

You might need topographic data if you don't have it already in the form of the design plan. Don't forget offsite watersheds.

There's no push-button answer for this. When I taught hydrology at the college level, my students would typically be able to handle the task you describe by about mid semester, maybe a little after. Then we'd spend the second half on reservoir and reach routing. Sometimes colleges even break the task into two classes, one for hydrology, one for open channel hydraulics. Open channel hydraulics itself can get very complicated, and is treated at the grad school level, but you shouldn't need to get that far.

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

RE: Culvert Design Requirements Help

@ beej67 - Thank you for the information

RE: Culvert Design Requirements Help

Beej67 - thanks for the USDA link. I'm not designing any culverts right now but
I found some useful manuals that might come in handy one day.

RE: Culvert Design Requirements Help

Do you have the culvert data available?
you can use HY-8 software program to check the parameters you are looking for.

HY-8 is free and lookup tutorials. That should get you started. or you can post the plans you have in front of you and will take a look.

RE: Culvert Design Requirements Help

Thank you all for your post. I was able to provide the calculations needed.

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