Export to HEC RAS: Reversed Flow Direction

[Neilw_05]

When I export my channel and cross sections to HEC RAS using the HEC RAS export tool in C3D 2012, the channel flow direction is backwards when imported to HEC RAS and the cross sections are reversed as well. My user drew the cross section sample lines as polylines from left to right when looking downstream. I used these polylines to create the sample lines but C3D does not honor the direction of the polylines so the sections are from left to right when looking upstream. The export tool does not seem to take this into account and thus everything is backwards when imported to HEC RAS. How do we get this to work?

 C3D 2012

[wfberry]

Neil:

I am not a Hec-Ras guy but I am thinking you would need the River Analysis extension for this to work in Civil 3D.

http://labs.autodesk.com/utilities/civil3d_river/

Bill

[Neilw_05]

Thanks for the tip Bill. I was not aware of that tool. I'll give it a try but it is not really a permanent solution since it expires in a couple of months. I would think the HEC RAS Export tool should be capable of generating a proper file. I'll file a support ticket.

These support issues are really disruptiing my deadlines!

[Matt.Anderson]

Neil -

[J_Nail]

I am having a similar problem.  I exported my flow line alignment (drawn from upstream to downstream) and cross sections to HEC-RAS.  The geometry schematic in HEC-RAS shows the proper flow direction and the cross sections are stationed correctly.  However, when I added my bridge model it shows the upstream x-sec as the downstream x-sec and vice versa.  I'm not sure if it is a Civil 3D export issue or a HEC-RAS glitch.

Let me know if you figure anything out.

[Neilw_05]

I'm struggling with how to get the channel alignment oriented from upstream to downstream while HEC RAS requires the stationing to be from downstream to upstream. The HEC RAS export tool would work fine if I draw my alignment from upstream to down stream but the stationing will be wrong. How do we do this?

[J_Nail]

I'm not sure if this will help you, but you can manually reverse the flow direction in HEC-RAS by doing the following:

http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=15128496&linkID=9240697

Geometric Data editor > GIS Tools > Invert Lines Table > Flip Coord. Order

[Neilw_05]

I saw that tool but I didn't think it was for reversing the flow direction. Won't reversing the coordinates of the channel alignment actually flip and mirror it? I don't want that.

[J_Nail]

I believe that it does reverse the flow direction.  I messed around with it and on my Geometry schematic it changes the flow direction arrow.  It might be worth a try- only takes a second

[Matt.Anderson]

It flips the coordinates order of draw (ie, position 1 thru 54) determines the flow direction.  Flip reverses those positions so that cooridnate pair 54 is now in postion 1.

It does NOT flip X,Y or N,E. 

[Neilw_05]

Thanks for that insight Matt. My user has imported the GIS data but the Reach Invert Lines option is greyed out.

Sorry but neither of us have experience with HEC RAS.

[Grimes_MG]

You have to use the Geometric Data --> GIS Tools --> Reach Invert Lines Table command directly after importing GIS information, otherwise, HEC-RAS won't let you modify it.

[wayne]

I am experiencing the same problem as Neilw while running C3D 2015. I would respectfully ask the Autodesk team why they haven't permanently resolved this issue after so many years for such a common civil engineering application. We understand that technically savy engineers have already developed patches for this problem, but these extensions remain propietary. So, I would imagine Autodesk software developers could tackle this with even a modest effort in the very near future. -wn

[klangmaak]

I simply reversed the direction of my alignment in C3D (so that chainage 0 is at the downstream end of the River).

In HEC RAS, the most downstream section must always have the lowest Station Number.  When you use the "Export to HEC RAS" function, C3D simply assigns the chainage as the Station Nr.  

Hope that helps

[Hidden_Brain]

did you compare your hec-ras cross sections with civil 3d cross sections after import?  are the ras sections mirrored?

*edit: double post, cannot remove

[Hidden_Brain]

did you compare your hec-ras cross sections with civil 3d cross sections after import?  are the ras sections mirrored?

[klangmaak]

It seems that the cross section stationing is reversed..., ie what should be on the left bank is on the right bank in HEC RAS and vice versa.

You can fix that in HEC-RAS.  In the Geometric Data Editor, go to GIS Tools --> GIS Cut Lines --> Reverse XS Stationing and Cut Line Data, select the affected Sections --> OK.