How do you size an area drain?
How do you size an area drain?
(OP)
I am working on a small site (6000 ft^2) that drains to one area drain. I am relatively new to hydrology, but would like to determine the size of area drain required. I already calculated the Q to be 0.5 cfs. How do I do this?
Thanks,
Jeff
Thanks,
Jeff





RE: How do you size an area drain?
RE: How do you size an area drain?
When you say "area drain" I guess you are talking about a detention / retention basin. The short answer: To determine your requirements, you need to find the difference between pre- and post development flow rates. I recommend using tr-55 or Hydrocad to find the difference. After cranking through the software (inputing curve #'s, slopes, flow characteristics, etc.) the software will give you the volumetric storage needed in acre-feet.
I said the "short answer" because you may have to account for a lot more than meets the eye. 6,000 Sq. ft. is dang near imperceptible as far as being a stormwater influence. Then again, it might be a matter of where you live- our 100 year event is 4.2"
If you are talking about a drain pipe to collect .5 cfs, I would recommend flowmaster. You input cfs, manning #, slope of pipe, diameter, etc. to find unknown variable. We also use flowmaster to determine r.o.w. capacities for 10 & 100 year flood conditions.
Sid.
RE: How do you size an area drain?
RE: How do you size an area drain?
If you are only getting .5 cfs to it, and located on a reasonable grade (or in a sag), a standard 24"x48" inlet should do it.
For calculations, FWHA HEC12 is the standard in the US.
RE: How do you size an area drain?