How do I create HEC-RAS cross section with 0 sta at center

[Ekenny_G]

HEC-RAS newbie here.
I am trying to create a HEC-RAS cross-section with 0 station at the center of the stream.
I draw the cross-sections in Bentley Microstation and then use inroads to export to HEC-RAS.geo file.
How do i get the cross sections so that everything left of the stream has a negative distance and everything to the right has a positive distance?

 

[gbam]

I do not know. I have a work around, however. We set the centerline to constant station, say 10+00 or 1000. We place our XSECs looking downstream and make sure the extent of XSEC to left is 1000-units. This approach will make sure the CL Station is 1000.

 

[Ekenny_G]

gbam,
so there is really no straight tool to do this other than manually entering the xsections stations yourself.
Also, in HEC-RAS Cross Section editor, what is the "Downstream Reach Lengths" meaning.
I imported my x-sections and some of those values are 0. I get error message when i try to run it that the LOB, ROB has to be greater than zero.

 

[gbam]

I recommend that you review the HECRAS Users, Hydraulic and Applications Manuals. This will help you properly code the data into HECRAS. Once you know what data needs to be entered in to HECRAS for a proper hydraulic model, then you can set up and use INROADS to extract your data. You will need to incorporate break-lines into your surface if you want INROADS to delineate your bank stations etc... Also, there is a specific way to create your alignment and draw your cross sections so they properly extract from the dtm. There are specific items that you need to hand enter as well.

 

[Ekenny_G]

Thanks Gbam, I have already extracted my cross section data from inroads dtm (LIDAR) and imported into hec-ras. Just that after importing cross section data, the zero station is at the end of the cross section stations. The issue is getting the cross section zero station to be a the reach line or stream centerline.

 

[cvg]

the zero is always at the end, no option

 

[beej67]

In a usual HEC-RAS file, you can have the zero be anywhere along the section stationing, with negative values to the left of zero, but the river station starts at zero at the downstream most point and works upward from there. Typically when exporting sections from a CAD environment, the CAD environments like to start their sections at zero from the first spot you pick when you're defining the section. I presume Inroads does it like that.

If you're getting zeros on downstream reach lengths, chances are good that you have to cut 3 profiles down the creek, not just 1. One for left overbank, one for right overbank, and one for centerline. You should spend some time reading what HEC-RAS actually does before going any further. It's a complicated piece of software, and there's a lot of nuance to it.

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http://www.campbellcivil.com

 

[Ekenny_G]

Thanks for the update. Just started working with HEC-RAS and learning how this thing works, starting with a basic channel and then adding culvert crossing. We'll have to start somewhere.

 

[gbam]

Beej67 is correct; however, I do not think the zero @ CL is achievable using INROADS.