×
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 Output Quirks

HEC-RAS Output Quirks

HEC-RAS Output Quirks

(OP)
I'm relatively new to HEC-RAS, and I have built a model of a small system to simulate the passing of a discharge (100-Yr) hydrograph of a large stormwater basin.  In the first few time increments, the model computes huge flows (about 1000x what the input hydrograph, sometimes negative).  After that it settles down and gives a relatively believable output.  Is it OK to just ignore the rough beginning of my output, knowing it is wrong?  The entire time of the simulation is about 10 hours, and the beginning rough spot is only the first 30 minutes (when the actual flow is less than 5% of the peak).  What I really need to know from the model is the peak elevation only, to be used for some flood high-water mapping.

Thanks,
Dan

RE: HEC-RAS Output Quirks

You may have a problem with your initial conditions assuming your inflow hydrograph always has enough flow. HEC-Ras hates to run "dry". Try adding some initial flow and minimum flow to your hydrograph. I would start small, say 50cfs, and work up. Sounds like your model runs once there is enough "water" in your channel. Since you are concerned with the peak elevation adding a little at the end and beginning should not affect your peak elevation.

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