Culvert Analysis/Modeling 2

[arellanoma]

Can anyone share their thoughts on how to approach modeling a culvert that contains two culvert pipes? I've been asked to analyze the capacity of an existing culvert that contains a 48" RCP and a 36" RCP. The 36" pipe is offset to the right and up in comparison to the 48" pipe. Any advice is appreciated.

Thanks

 

[francesca]

HEC-RAS, WinTR-55, various storm sewer software applications, etc. What do you have available to you?

 

[arellanoma]

Unfortunately, we only have the hydraflow express program than accompanies Civil 3d (09). Our IT department is outsourced and only this program is "authorized" to be used. I'm planning on downloading HY-8 from the FHWA website and see if I can use it at home.

Do you recommend a different program? HEC-RAS?

 

[sam74]

Are the two culverts at a stream crossing or is it more for a storage outlet? That might make a difference on how best to model it.

If you just need the capacity and not necessarily a model, on the FHWA webpage you should be able to find a section in one of the publications that contains nomographs for pipe flow based upon the head and pipe size. With this information and the maximum head you could determine the capacity with little effort.

I'm not familiar with hydraflow express only hydraflow hydragraphs and hydraflow stormsewers stand alone versions. What will express model, ponds and pipes?

 

[arellanoma]

Sam74,

Thanks for the info.

The two culverts are for a stream crossing. A developer was conditioned to increase the capacity of the culvert and they installed the 36" pipe instead of replacing the 48" culvert pipe.

We have hydraflow hydrograph, stormsewers, and express. Express has a culvert option which allows us to analyze culverts.

I used FHWA's HEC-22 manual and nomographs to determine the capacity and headwater for the 48" pipe. I'm not sure how to include the 36" pipe into my analysis. I understand that if the flow exceeds the 48" pipe, headwater will rise and then flow into the 36" pipe. I'm not sure how I would determine the total capacity and see if the stream will overtop the existing road.

 

[francesca]

Hydraflow should be able to handle it no problem. I used Hydraflow Hydrographs before Autodesk bought them. They're good software packages and the documentation of how to use them are on the Autodesk website.

 

[froude]

Arellanoma,

I have not used Hyrdaflo but, as it has been mentioned above, I do know that it will handle the scenario that you're describing above.

HEC-RAS would also suffice for your analysis. I'm sure you're aware, but just in case, it is available for free download from the US Army Corps.

Also, I have heard from people that Bentley Systems, Inc. will provide a limited trial version of CulvertMaster (this used to be a Heastad program). This program will also probably suit your needs. However, I think you'll actually have to contact them; it's not available for download.

Good luck!

 

[arellanoma]

Thanks for the info Froude.

 

[TerryScan]

One can analyze a crossing of multiple varied culverts using FHWA's HY-8 software.

 

[gbam]

One can create rating curves based on a total flow rate. First establish a tailwater section rating curve and then create rating curves for each culvert based on the tailwater. Some iteration will be required to determine the flow distribution and the resulting common headwater elevation. Back in the day we had to do this exact process before software could evaluate different sized culverts with common tailwater pool.

 

[arellanoma]

Thank you TerrySan & gbam for your help.