HEC-RAS Crosssection at bend in stream

[MeemaCE]

As you can see from the attached photo, one branch that enters a culvert encounters the culver's wingwall perpendicularly. I think I need another cross-section to model this. See attached plan view; additional xsec would be between 199 and 202 to catch the perpendicular approach to the wingwall. Is it ok if the xsecs cross each other? I think that's what would happen if I cut it properly. Any advice appreciated. Thanks!

 

[RWF7437]

Short answer is NO, cross sections may not cross.

They can "bend", however, in order to avoid crossing.

 

[MattZ99]

That is correct, HEC-RAS cross sections cannot cross one another. You can take the obstruction due to the wingwall into account using a the Blocked Obstruction option in the cross section editor.

 

[gbam]

If this culvert is the inlet that the stream enters, you can take another approach. You can evaluate the culvert externally and start your backwater analysis from the culvert headwater. It appears that the culvert is 90^ to the approaching stream --> additional losses to turn the corner. This approach would provide a conservative analysis upstream assuming that the entire velocity head is lost.

 

[MeemaCE]

Thanks for these replies. They are very helpful. I want to use Matt's solution, however the Obstruction tool only allows for a single elevation (not sloping, like this wingwall is). Is there any way around this, or a similar tool I should use?

 

[MattZ99]

There is no tool for sloping blocked obstructions, just sloping abutments at bridges. A work-around could be to use the Multiple Blocks option and enter several, thin obstructions to simulates the sloping wingwall. It won't be perfect, but it may be a close enough approximation for your needs.