IDF constants 1

[cimmeron]

I have moved from Denver to Jacksonville, Florida. In Colorado, I used the FAA method of computing detention basin volumes. I would like to use the same method in Florida but cannot find the three" C" factors for Jacksonville. Can anyone point me to a surce.

 

[RWF7437]

I'm not familiar with the FAA method of pond design but offer the following suggestions:

Contact the Florida DOT. They will have an hydraulics manual, IDF curves, and probably much information of value to you.

Also ask others what methods are used in Florida. Unless your projects are all airports you will almost certainly find that most people do not use the FAA method unless they are required to. Cities, counties, water control districts and others have their favorite methods and will generally require you to use them, even if you don't agree with them !

Good luck

 

[jamsberry]

If you are referring to what is also know as the "bowstring" method, you will not likely be able to use that in Florida. As the previous post said, Contact Florida DOT, but also contact the local jurisdictions including the stormwater managment district you'll be working in to find out what the requirements are for whichever jurisdiction you are working in will be.

 

[LHA]

I can't comment on FL or any other region of the world. I can verify with fair certainty that noone in PA, MD, DE, NJ uses or would have a clue how to review this FAA method. It was not mentioned to me at Penn State University during either my undergrad studies or my PE review course.

But, if you can justify its applicability and you sit down with the reviewer first, it may fly.

Good luck

 

[lsp01]

As a stormwater engineer in Jacksonville for over 8 years, I can safely say that we don't use the FAA method.

You need to contact the St. Johns River Water Management District (

http://www.sjrwmd.com)

and get a copy of the design manuals. Florida has many requirements that other states do not, specifically treatment volume requirements, attenuation, recovery period, permanent pool etc. These manuals will provide an excellent reference about how systems are designed here.

The FDOT is also required to meet the Water Management District criteria, but they also require design to a "Critical Duration Storm". Information about these requirements is available in the FDOT Stormwater Managment Facility Handbook. FDOT design is only required if you are connecting to or designing an FDOT system.

All bu the simplest systems are typically designed using stormwater models.

Good luck and welcome to Florida!
If you have specific questions just ask.

 

[jjn]

just in case anyone's interested...

the FAA detention design proceedure is referenced in "Airport Drainage", Federal Aviation Agency, 1966, I first found it in Maidment's "Handbook of Hydrology", pg. 28.27-28.28. It is rational method based proceedure and assumes that rainfall volume can be expressed as a time integral of the IDF curve - cumulative runoff (inflow) is
Vin = C*i*A*T
and the cumulative outflow volume is
Vout - k*Qout*T
where Qout is the maximum outflow rate and k is an adjustment coefficient based on the ratio of maximum outflow to peak inflow. The T's are whatever increment of duration makes sense - expressed in seconds. Dentention volume is based on a mass balance and represents the maximum difference between cumulative inflow and cumulative outflow.

its an easy spreadsheet as long as you have coefficients to generate a local IDF curve - which is what i believe cimmeron was asking for. those should be available from the local jurisdiction or from the state department of transportation.

the method has all the limitations any of us would put on the rational method, plus a few of its own. i've never done work in a jurisdiction that accepts it outright as a standard; i've talked my way into using it a couple of times. it is generally not worth the effort to persuade if the local requirements are sensible and sound; as dorothy used to say "i don't think we're in kansas anymore, toto."
however, it does serve as a quick way of getting a reasonable estimate of volume for planning or initial design purposes or to verify an initial estimate of available volume based on site constraints.

like i say, just in case you're curious...

jjn

 

[ptmoss]

The references I remember to FAA method (I've never really used it as TR-20 or Rational seem to predominate in my neck of the woods) limited its use to flat (read 2% and less slopes) drainage areas. Which always made sense to me as I assumed the method was developed for use at existing airports.