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W Beck

Cross section editing after Network Schematic creation

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Posted (edited)

I created a HEC-RAS network schematic, and was in the initial stages of running HEC-RAS when a series of errors occurred. These errors stemmed from the fact that some of my cross sections did not intercept the left overbank (LOB) and / or right overbank (ROB) lines (middle image). Compare to the top image, where the cross section intercepts both LOB and ROB. I did not realize this was critical when creating the cross sections in WMS. Extending the cross sections beyond the LOB / ROB would seem to solve the problem. As you can see in Image 3, when the cross section does not intercept one of the bank lines, it assigns both bank stations to the zero point. 

My question is - is there a way to edit the cross sections (i.e., extend them) after a network schematic has been created? Since I merged all extracted cross sections with field data, I'd hate to go back and redraw all cross sections, extract again, and then merge again.

I attempted to draw extensions onto the cross sections in WMS (create feature arc tool, then use "node-to-vertices" option to create a single line), however, this seemed to "unlink" the cross section with my merged data. 

So, is there a quick way to extend cross sections beyond LOB / ROB centerline coverage, to eliminate the HEC-RAS errors? Without having to redraw / extract / merge all cross sections again. 

Thank you!

Image 2.PNG

Image 1.PNG

Image 3.PNG

Edited by W Beck

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Hi,

There is a way to re-extract and update only selected cross sections but it's not an easy procedure and would require you to edit some of the WMS .map and cross section database files using a text editor.  I guess I don't really recommend this approach.

I guess you have a couple of options.  One is the approach you mention, where you extend any cross sections that don't intersect the bank lines so they're beyond the bank lines.  This would require you to re-extract all your cross sections, and your edits based on survey data would be deleted.  You would need to re-enter your survey data for each of your cross sections in this case.  This should not be too difficult since you should already have the survey data saved as a cross section database file.  It would just be time-consuming, especially if you have lots of cross sections.

Another approach is to edit each cross section's geometry and point properties by going to the cross section attributes | Assign Cross Section | Edit and then adding the left and right bank stations manually into the Point Props window.  The drawback of this method is that your left and right overbank lengths will not be computed by WMS for the cross sections where the left and right banks are manually defined.  When you run HEC-RAS, you will get an error message for each of these cross sections.  You can then compute the left and right overbank lengths for these cross sections using the measure tool in WMS.  You would have to re-enter these lengths in HEC-RAS each time you export your model from WMS.

So it may be worth it to you to update your cross section arcs in WMS, re-extract the cross sections, and re-merge your surveyed cross sections, but that's up to you.  I agree that it would be nice to just update selected cross sections in your cross section database file, but this option is not yet available in WMS.

Hope this helps,

Chris

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