pre and post development runoff calculations 1

[azukarita]

Hello

I am trying to do a stormwater management / drainage report per city of Paterson, NJ requirements that includes the following:

- Pre and post development runoff calculations for runoff for 2 and 25 yr storms.
- Design stormwater management facilities zero net increase in runoff rate for the 2 and 25 year, one hour storms.
- Design stormwater management facilities (detention ponds, control structures, seepage pits, etc) per Residential SIte Improvement Standards NJAC 5:21.

Please help! i'm right out of school and is the first time for me doing this in my new job. Any contribution?

Thank you!

 

[beej67]

Rational Method is a very poor way to develop hydrographs for a storage analysis, regardless of the site's size.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[azukarita]

SMIAH : shouldn't I be using the watershed area instead with a weighted Runoff coefficient?

 

[SMIAH]

Yes if you only change a percentage of the 7500 sq feet.

e.g. 2500/7500 sq feet x 0.45 + 5000/7500 sq feet x 0.15 ...