×
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

Lagoons and Modelling

Lagoons and Modelling

Lagoons and Modelling

(OP)
Hi,
I have an odd stormwater modeling question. We have a 50ac man made lagoon with a single 12" culvert discharging water to a ditch from the lagoon (no outlet structure). NO stormwater reches the lagoon from outside the 50ac. We are just doing a model of the existing lagoon and outlet structure to determine drawdown times and what size pipe we are able to replce the 12" with. In modeling the 25yr storm hitting the lagoon I would think you would use a CN (santa barbara methology) number of the existing soils in the lagoon as you will still have infiltration. If it was a lined lagoon would you use a CN of 98 and treat it as impervious? I think its just a simple catchment to pond to outlet model, with the catchment being the lagoon/pond area.
Thanks

RE: Lagoons and Modelling

Since the rainfall is essentially falling on the surface of the pond, you would use a high CN (98+) to allow for (almost) complete interception of the rainfall. If there is no watershed area beyond the lagoon, and you assume no infiltration or discharge, the peak depth in the lagoon will be the same as the rainfall depth, correct? So a 5" event will give 5" of water in the lagoon (Assuming a flat bottom) Adding an outlet device will obviously reduce the peak WSE. But it's going to take a long time to drain the entire 50 acres, unless the bottom is sloped to create more head at the outlet. Of course, all this assumes the lagoon is empty at the start of the storm.

Peter Smart
HydroCAD Software
www.hydrocad.net

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