Split flow modeling - roadside ditch and culvert

Question

Split flow modeling - roadside ditch and culvert

msengelen (Civil/Environmental)

(OP)

9 Nov 20 04:54

I'm trying to determine if there is a good way to use Hydrocad model split flow flow for the following described conditions.

Existing condition: There is a roadside ditch and a culvert crossing under the roadway. The roadside ditch contributes flows to the culvert and the ditch continues along the roadway past the culvert. I need to determine the amount of the split flows in each direction, through the culvert and through the ditch.

Proposed condition: Same as above, except a driveway and culvert is proposed just downstream of the existing culvert. I need to determine the amount of the split flows in each direction, through the existing culvert and through the proposed culvert.

Does someone have a good idea on how to model this?

psmart (Civil) · Answer 1 · 2020-11-09 15:50:32

To model a flow split between two culverts you would set the routing for one culvert to primary and the other to secondary. Same for the ditch/culvert split, modeling each with the appropriate outlet device.

You can also use a link to model a flow split according to a specified flow threshold and/or flow ratio. But using primary/secondary routing is generally preferred. For details see www.hydrocad.net/diversion.htm

Peter Smart
HydroCAD Software
www.hydrocad.net

msengelen (Civil/Environmental) · Answer 2 · 2020-11-10 00:48:28

Thanks for your reply. I modeled the proposed condition per your reply by routing for one culvert to primary and the other to secondary, and that worked fine. However, I am still not sure how to model the existing condition with the ditch and the culvert. How should I use a pond to model this (or should I use something other than a pond)? What are your thoughts on how to model the existing condition?

psmart (Civil) · Answer 3 · 2020-11-10 01:37:59

You would need to use a pond for the primary/secondary option. Even a zero-storage pond would work. For the ditch scenario you could model the ditch flow using a special outlet, a weir, or the new reach outlet added in HydroCAD 10.1

Peter Smart
HydroCAD Software
www.hydrocad.net

msengelen (Civil/Environmental) · Answer 4 · 2020-11-12 16:51:25

RE: Split flow modeling - roadside ditch and culvert

msengelen (Civil/Environmental)

(OP)

12 Nov 20 16:51

Thank you.

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