Large Drainage Area into Small Pond

[cfj104]

I have a large site (16 acres) that drains into a small pond (146,000 gal) with a 12" discharge outlet. I am trying to evaluate various options for increasing the time of concentration on the site in order to attempt to lower the peak flow rates. One option I am evaluating is installing some smaller interception trenchs to slow down the water, however, the routing results for these smaller ponds is resulting in higher outflows then inflows and oscillations in the hydrograph.
I am assuming that part of my problem is the large drainage in comparison to the small holding capacity of the trench, is this correct? What would be the best way to correct this error in the model? (I have already adjusted the routing value).

Thank you.

 

[psmart]

I assume there are warning messages associated with these problems. Please click each message for details and recommendations.

For example, you may have overfilled storage, which can occur is you fail to define storage to some point above the crest of your weir. For details see

http://www.hydrocad.net/overfilled.htm

If you have further questions please post the exact message or your HydroCAD project file.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[TerryScan]

Without more information, I have to make some guesses, but it sounds like you don't have enough storage for 16 ac. of runoff. I imagine one could increase Tc to absurd times and still you won't have enough storage.

Try a direct entry Tc. See if you can increase it to a point where you get a flow rate you are looking for, or realize this is not even possible.