Culvert Design

[ptr]

I have to design a 400ft long box culvert. We have a stream that will transition into the box culvert as it travels under pavement and then transitions back into a stream. How do I properly model this in HydroCAD or PondPack?

 

[BDAnderson]

In HydroCAD I would model the upgradient stream as a Reach with the appropriate inputs to model the stream characteristics, model the culvert as a second Reach with appropriate inputs to model the culvert characteristics, and then model the downgradient stream as a third Reach.

You'll have to make sure the Subcatchments feeding your stream are set up and connected to the Reaches to accurately model the entire watershed feeding into the stream (the subcatchments may be rather large if this is a perennial stream).

I'm not familiar with PondPack.

Hope this helps,

Derek

 

[ptr]

Thanks BDAnderson...

I thought of that, but modeling the culvert as a reach does not take into acount the entrance losses (k value) from the culvert's entrance headwall.

What if I model the upgradient stream as a reach, then model the culvert as a pond with no storage and with the outlet serving as the culvert, then have a second reach for the downgradient stream?

 

[gbam]

If you are looking to route through the system I would use HECRAS to establish the hydraulic rating for the box culvert and then code that rating curve into a hydrologic model. This is one example approach to incorporate the hydraulic considerations of the box. I am surprised that the either of the two models you mentioned do not have a hydraulic component.

 

[psmart]

When using HydroCAD, most culverts should be modeled as a pond with a culvert outlet. This will account for entrance losses and detention (ponding) at the inlet. HydroCAD WILL calculate a rating curve for the culvert including inlet, outlet, and barrel conditions.

So your model would have a pond w/culvert (for the road crossing) followed by a reach for the open-channel flow downstream of the culvert.


Peter Smart
HydroCAD Software

http://www.hydrocad.net