Detention Ponds and WSE
Detention Ponds and WSE
(OP)
How do I calculate 100 yr WSE for a proposed detention pond?
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RE: Detention Ponds and WSE
Peter Smart
HydroCAD Software
www.hydrocad.net
RE: Detention Ponds and WSE
RE: Detention Ponds and WSE
Thanks
RE: Detention Ponds and WSE
RE: Detention Ponds and WSE
1. Do you know which type of hydrologic method you will be using? Will it be a unit hydrograph? Modified Rational? This is something you need to know ahead of time and may be dictated by your local municipality or reviewing body.
2. Do you know what your target release rate is? This may also be governed by the above-referenced entities.
Once you determine your methodology, you will need to find a program to perform your reservoir routing (or do it by hand/spreadsheet).
Some free programs that will do reservoir analysis include HEC1, HEC-HMS, and EPA-SWMM (but I believe these only do unit hydrograph methods). Several licensed software including PondPack and XP-SWMM will also do detention computations.
For modified rational detention routing, there may be spreadsheets available online (or it would be relatively easy to come up with one.) Good modified rational detention examples can be found in "Stormwater Conveyance Modeling and Design," which is a manual published by Haestad (now owned by Bentley). Some time ago, Haestad had published PDFs of this for free download. I don't know what the current availability of this document is.
Regardless, the concept as described by the users above is still true. You determine your post-developed runoff and route that through your proposed pond volume and your selected outlet structure. This will then tell you your max pond volume and max 100-year WSEL.
RE: Detention Ponds and WSE
I hate to be a sourpuss, but this is something basic that you should have learned in school, and its important enough that you should probably hire someone more familiar with it to get it right if you are unsure about how to do it. If you do it wrong, and something fails, it's your butt.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Detention Ponds and WSE
Once you have the required 100 storage volume, you can set up your own pond to accommodate the volume and interpolate the 100 yr WSEL from the stage-storage curve for it.