×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

hec-ras program
2

hec-ras program

hec-ras program

(OP)
How do you define your last x-section so tht the program interprets the right and left bank properly. Every thing I have tried switches my right bank to left unless I put a false x-section 5 feet down stream. any sujestions?

RE: hec-ras program

I have never encountered that problem.  What version of the program are you using? By last cross-section, do you mean the first downstream cross-section or the last upstream cross-section? If you add a cross-section 5' downstream, do you get the same error on the newly-added ("false") cross-section?

I would suggest that you check the stationing along your cross-section.  Make sure that the LOB is stationed from 0+00.00.

RE: hec-ras program

The first cross section is always the  section farhest downstream.  As such, it has the lowest numerical station number.  Also, the left and right bank distances downstream are left blank.  That's how HEC-RAS "knows" it is the most downstream section.

Also, be certain no two cross sections cross each other.  HEC-RAS can't understand this geometry even though it may be phsically possible.

Also HEC-RAS insists that distances along a cross section increase from left to right.  HEC-RAS calls these distances "stations" even though any surveyor would call them "offsets".  You may use negative distances but you cannot use increasing and decreasing distances.

Good luck

RE: hec-ras program

Quote:

Also, be certain no two cross sections cross each other.  HEC-RAS can't understand this geometry even though it may be phsically possible.

My understanding is that the cross-sections are supposed to be perpendicular to the direction of water flow.  If it is physically possible for cross-sections to cross, then, by this definition, water can flow upstream and/or be in two places at the same time.

If you're defining cross-sections around a tight meander, instead of crossing cross-sections, you should have cross-sections that are almost on top of one another on the inside bank, with downstream reach length equal to zero. I can't think of another situation that might tempt the modeler to have cross-sections that cross, but I'm happy to be drawn into debate on any someone can suggest.

RE: hec-ras program

To Franseca,

Surveyors are perfectly happy to survey, plot, and report cross sections which cross each other.  At least all the surveyors I've worked with over 45 years have been able to perform this feat.  But, HEC-RAS is a "model" of the surveyor's world and, as such, cannot tolerate such ambiguities.

Thanks for your post.

good luck

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources