×
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

IDF Curves

IDF Curves

IDF Curves

(OP)
Say you have a catchment and you know the maximum flow that can go through the pipes. Which IDF value would you state as the event that can flow through this network? I.e. say the intensity is 30mm/hr this could correspond to a 2 year 10min storm or a 100year 1 hr storm:
http://www.idfcurve.org/chart_samples/chart_sample...
Which is the best to choose and why?

RE: IDF Curves

I would choose whichever curve is the regulatory standard in your location for storm sewer design.

RE: IDF Curves

kazzy - the design storm frequency and duration is set by local or regional regulations as TerryScan stated above. There are soooo many different combinations of storms and etc.. that governing agencies set their guideline.

RE: IDF Curves

Typically in municipal design, the majority of the storm sewer network pipes are sized for the Minor Storm events. The Minor Events are typically the 2yr or 5yr. That's because it is not economically feasible to size the network for the Major Events. The Major Design Event is typically the 100 year, and is typically carried on the street surface, within the ROW, with safe freeboard relative to structures.

RE: IDF Curves

The municipality usually has in the stormwater ordinance which storm to use for design purposes. I always design for a 25 year storm. Once you know the storm, the time of concentration will dictate the correct duration and thereby rainfall to use.

If there is no guidance on the storm frequency to use, pick what storm event you are comfortprable with.

RE: IDF Curves

Around here, it's not uncommon to see municipal storm sewers designed for the 25, and culverts designed for the 100. Depends a lot where you're at.

If you're trying to back your way in to determine what the capacity storm is for your culvert, then solve for flow using Manning's or whatever, check inlet/outlet control, and plug that into the Rational Equation to determine capacity intensity. Then determine your Tc and read up on your idf curve to determine the capacity storm.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

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