HEC-RAS and Wrong Stations

[Anonymous]

Alright fellas. I have created alignments for two reaches on a site. On reach 1 I have 12 cross sections ranging from - to about 12+00 in stationing. Reach 2 has 7 cross sections ranging from 0 to about 6+50. I export .GEO files of these reaches through the Autodesk supplied HEC-RAS export tool.

Upon importing these files in the Geometric Data section of HEC-RAS 4.0 the reaches look correct but the stations are not in order! So station 1+28 may come between station 3+84 and 7+13. I took a quick glance at the GEO file and it looks to be in order with correct stations and elevations.

I really don't want to open up ye old land desktop.What have you experienced with this?

[Anonymous]

Attached Image.

[Matt.Anderson]

dlmanning -



Civil 3d operates on a left-to-right upstation view of an alignment and cross-sections.



HEC-RAS operated on a left-to-right downstation view.



River Stations should start lowest station and proceed upriver to the higher stations.



If you flip your alignment in Civil 3d, the GEO file operates correctly - however, the stations for the cross-sections are incorrect.



If you flip you reach in HEC-RAS, you can correct the reach, BUT re-importing the data will now gets messed up.



Christopher Fuggit posted a possible solution to the coding by writing out the coordinates of the reach in the expected GEO format. I would highly recommend that revision. (See http://blog.civil3dreminders.com/2008/10/hec-ras-extension-bonus-feature.html)



Matthew Anderson, PE

[Anonymous]

Thanks for the link Matt. I'm not sure I made it clear before but HEC-RAS was incorrectly stationing the reach not the cross section stations. I did find out why this was happening.

I have a reach alignment starting downstream going upstream. Civil 3D creates cross sections from right to left looking downstream. That is the opposite of what HEC-RAS wants (Like you said Matt). Thats an easy fix. Just reverse all of the cross section stationing in HEC-RAS (TOOLS>REVERSE STATIONING DATA). I found out that since I drew my cross sections by polylines and they were not orthogonal to the reach (per the request of the engineer I am working with) it caused HEC-RAS to confuse the information.

When I created those cross sections at the same stations but orthogonal to the reach alignment, HEC-RAS was fine with the information. Also with all cross sections orthogonal except for where a road crossed, HEC-RAS correctly stations the reach. Compare the first PNG attachment with the one in this post to see the difference. Pay attention to the end stations on reach 1.

[Matt.Anderson]

Yes, you discovered the limititation of Civil 3d and the cross-sections stationing by way of polylines. (I didn't look at the image until this morning and yes I see the issues).



One item that may help is added you polyline sections as sample lines to you alignment. When you do that, your sample line, when selected, will show you "where" it assumes your alignment station to actually occur. if you manipulate the section station grip and drag your sections grips, I think you can get it back to the way you want it.



Cross-sections for Hydraulics should be orthanginal to flow, not the alignment.



Maybe I'll blog this next week on civil3d.com...

Edited by: Matt.Anderson on Jan 30, 2009 8:25 AM

[Anonymous]

To clarify, the way the engineer drew the cross sections parallel to each other is the correct way? Is that what orthogonal to flow means?

And here you said "One item that may help is added you polyline sections as sample lines to you alignment. When you do that, your sample line, when selected, will show you "where" it assumes your alignment station to actually occur. if you manipulate the section station grip and drag your sections grips, I think you can get it back to the way you want it."

Are you suggesting to create samples at the appropriate station and then adjust the grips to change the orientation of the sample and that this would fix the afore mentioned problem of just creating sections from polylines?

[Anonymous]

Matt may not be available until tomorrow (Monday)
so I can offer one thing.  Orthogonal = right angle to "whatever".  So
as you can see in your diagram some of the sections are not perpendicular to the
flow of the channel.

Bill

style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

<dlmanning> wrote in message
href="news:6115794@discussion.autodesk.com">news:6115794@discussion.autodesk.com...

To
clarify, the way the engineer drew the cross sections parallel to each other
is the correct way? Is that what orthogonal to flow means? And here you said
"One item that may help is added you polyline sections as sample lines to you
alignment. When you do that, your sample line, when selected, will show you
"where" it assumes your alignment station to actually occur. if you manipulate
the section station grip and drag your sections grips, I think you can get it
back to the way you want it." Are you suggesting to create samples at the
appropriate station and then adjust the grips to change the orientation of the
sample and that this would fix the afore mentioned problem of just creating
sections from polylines?

[Matt.Anderson]

Parallel cross-sections would be consistent with a straight lenght of ditch only. The image you provided shows that the channel is not straight.



Without looking at the contours, it is a little difficult to assist.



As for the rest of your comments, let me finish my blog post and I should be able to answer those questions there.

[Anonymous]

Have a look a the River Tools from Steltman Software, it will take care of any of the import/export issues with HEC-RAS.
download it at www.rsteltman.com

River Tools will create sections from lines and plines that cross river channel,
plot the sections and Export geo referenced sections including cut lines, reach lengths and bank stations to HEC-RAS
You can draw banks or boundaries from HEC-RAS design back into C3D and stretch a 3d pline from new drawn banks to original ground surface

Dave Hill

[bedringt]

I was having a similar problem with cross sections popping into hec-ras out of order. This is addressed in the AU course called

CV118-5 The Floodplain Truth with AutoCAD Civil 3D by James Wedding

If you have an Autodesk subscription, the screen-cast is free to watch. I don't remember the particular solution off hand, and the screen-cast is about an hour long, but I think the fix for the glitch was something as simple as selecting all of the sample line labels before you export.

Ben

[O.Maille]

no need to worry;
http://pressreleases.autodesk.com/index.php?s=118&item=627
if you can be arsed fixing it, buy it Edited by: O.Maille on Mar 30, 2010 5:25 PM

[Anonymous]

You create 2 reachs, How you join them ? How you create the junction ?

[Hidden_Brain]

in the HEC-RAS geometry editor, click EDIT>MOVE, then move one reach with the tiny blue grip to snap onto the other reach, the software will prompt you to split the reaches and create a junction. double check the rech lengths to the junction under junction editor.

[DS00]

Good afternoon, 

I have a question regarding exporting sections from CIVIL into HEC-RAS that has to do with wrong positioning.

I'm still quite new to this software but as far as I know, HEC-RAS assumes the zero-station (x-axis) on the left side of the graphic (IMG01 - attached).

I was wondering if there is an easy way to import the sections from AutoCAD Civil, having the zero-station on the river axis, ie in the middle of the graphic with a negative (left) and positive (right) sides (IMG02 - attached). 

What I was naively doing so far was inserting point by point with its station and elevation values, which consumes a lot of time.

I hope I've explained myself clearly, thank you in advance for your time.

Regards.

DS

[MattAndersonPE]

DS -

The original design of the tool expected the user to use HEC-RAS to flip both the coordinates of the reach and cross-sections.  HEC-RAS supports that workflow in the geometry editor.

[Note that my prior comment in this thread occured when I wasn't a Autodesk employee... but now all my prior posts are now tagged as employee. ] 

[Hidden_Brain]

assuming that you want the zero at the lowest elevation point at each cross section:
1. export from C3D-import into RAS using RAS extension
2. flip reach and cross sections using RAS geometry tools
3. add Min Channel Elev Station to RAS standard table
4. note that station number, copy each cross section table in excel, then subtract the station value (from step 4) top down until that station value is found. this will make the stations to the left negatives and the station at the lowest point zero.

If zero does not have to be at the lowest elevation for each section, make a copy of the previous alignment from above (that you have already imported into RAS and flipped) and reverse its direction so that it has increasing station in the direction of flow. then:
1. set up sample lines for this new reversed alignment
2. set up multiple cross sections for the sample lines
3. In Civil 3D, right click on the cut section line in section view (one at a time)>properties, here i think you will find the section table with negative and positive stations. copy the table for each section, in RAS section editor, remove data and paste this table

not very elegant solution, but it will get you what you need. It will not be too difficult to set up a VBA routine to do the math in Excel after the paste. good luck!

[DS00]

Thank you guys for the help, I'll give it some tries and I'll let you know. Cheers DS