FEMA Zone A

[ugfest]

We have a project that is in a FEMA Zone A floodplain. However, it is no more than a drainage swale running through an agricultural field. The Zone A area continues up to the beginning of the swale. The uppermost portion of this swale has a drainage area of less than 4 acres, This can't be a FEMA floodplain. Is there a minimum drainage area in determining the FEMA Zone A boundary? All information I've looked at does not give a minimum drainage area.

 

[LHA]

There is no watershed critieria for delineating a FEMA flood zone. But what are seeing is an Approximated Study - a conservative "sketch" of an arbitrary elevation which mimics USGS 20' interval contours. It almost never follows the local contours to any acceptable precision (say, 2' intervals). It is not intended to, it is just a guideline...unless a Detailed Study was done, which will have sections enumated along the reach.

If you are in an A FIRM Zone, I don't think there has been a Detailed Study done by FEMA. Therefore, you are free to delineate one. A licensed engineer can model the reach. He or she will have to file a Letter of Map Change (LOMC, or LOMR) to make it legal with the Corp. But you may not even have to do that for local development criteria. You may just be able to delineate it.

Beware, doing this delineation could effectively (and legally) "rezone" the area as a Flood District, IF your local ordinance allows for that. This could backfire on you and make your development criteria more strict.

 

[ugfest]

Thanks for the info.....