ELEVATION CERTIFICATE ZONE A?

If it's an AE, it should have a BFE somewhere on the map. Sometimes is wavey lines that you have to interpolate between, sometime it gives a uniform BFE for the zone below the "Zone AE".

Zone A can be tricky. You're supposed to call around to see if you can find someone willing to state a BFE for that area. The first call should be to the local flood plane manager (probably someone in the building or permitting department). If it's in a subdivision of more than 200 lots (IIRC) the flood plane manager is required to determine a BFE. Around here, I've never had a flood plane manager decline to give me a BFE.

But, if you can't get a BFE, then there is a section on the back of page 1 of the elevation certificate form for Zone A (no BFE). Technically, I don't think you even need to run in an elevation at that point. All that section asks for is the relative heights of the building features above highest and lowest adjacent grade. I don't even think a surveyor has to fill it out or sign it.

Terry,
In addition to Pseudo Rangers response:
The LOMA application lists about four organizations that you should to call to check to see whether they have calculated any BFE for your site. The local town or city office, as Pseudo states, is one and the Army Corp of Engineers is another. If you find no FBE available, state that fact in your application to FEMA and request that FEMA engineers calculate the BFE. They will then do this for you.
Also, check the FEMA website for any LOMA's that have been granted for nearby properties. If You find any LOMA's, provide the Case number(s) in your letter. That will make it easier for FEMA to process your LOMA application.

Chris in NH

The most readily accepted sources for BFE in AE zones are the flood study profiles in riverine systems and the tables in lacustrine systems.

Adam is correct. You are not supposed to used the lines on the FIRM Map. You need to get the FIS and interpolate the profile, or the new DFIRM data.

> Adam is correct. You are not supposed to used the lines on the FIRM Map.

If that's the case, why are BFE contours shown on the FIRM, and why does Section B10 on the Elevation Certificate have a checkbox for FIRM as the BFE source?

Jim,
The FIS profiles provide greater detail as to the changes in elevation between contours. If your property lands on a contour of the FIRM, then you are OK to use the FIRM. However if your property lands somewhere between the contours, then you should use the FIS profile because the interpolation between contours is often not a straight line interpolation.

In other words, the FIRM contours do not show the changes in slope of the water surface between contours. The FIS profiles do.

It can make a difference. I did one just the other day where interpolation between contours gave a 0.5' difference than using the FIS profiles.

Remember, the contours on the FIRM are developed from the FIS, however the contours rarely occur at changes in slope of the water surface.

Cerroli said in regard to a LOMA

"If you find no FBE available, state that fact in your application to FEMA and request that FEMA engineers calculate the BFE. They will then do this for you."

Is this true? When I tried to figure out how to do a LOMA I saw instructions of "determine BFE" and I was refered to instructions for hydrology that's way beyond my capabilities.

In June 2010 I got a LOMA for a client in zone A by submitting data using USGS report 87-4111, by calculating the watershed area in sq. miles, etc. My BFE was 418.05'; the LOMA shows FEMA came up with 427.4'. the house and yard were on a bluff at 460'. My guess is that FEMA wants us to jump thru some hoops, and then they will use their own calculations anyway; which is fine, but perhaps there should be no such animal as zone A. D. Berry

I think they created Zone A as a cheap way to tell people to stay out of what appears to be a flood-prone area in general. The cost to establish a true BFE for all parts of all Zone A's would be outrageous on a nationwide basis.

I think you have to consider the FIRM and the FIS, especially in unusually shaped Zone AE's.

Another thing to consider regarding FIRM BFE vs. FIS BFE is that when dealing with lakes and ponds the BFE on the FIRM will be rounded to the foot while the FIS Summary of Stillwater Elevations will be to the tenth.

I don't think FEMA will calculate the BFE for you. You would have a hard time getting that from anyone if no flood study was done, although the County or State DOT might have that information if a bridge project was nearby.

I can see that possibly this could become easier in the future depending on what FEMA would accept. In Illinois, with height modernization in progress and new LIDAR DEM's available online, some cross sections should be able to be extracted that would be pretty close. And for the watershed Q number, the USGS Streamstats online service is getting a lot of regulatory agency respect. With a couple of cross sections and a Q, the FEMA Quick2 program should be able to provide a water surface elevation.

The question remains if FEMA would accept those data sources for the Quick2 inputs.

> The question remains if FEMA would accept those data sources for the Quick2 inputs.

FEMA Procedure Memorandum No. 61 - Standards for Lidar and Other High Quality Digital Topography
http://www.fema.gov/library/viewRecord.do;jsessionid=B88DF0A0B79FDB75658E3BEB55F644FA.WorkerLibrary?action=back&id=4345

The attachments align FEMA’s high quality topographic specifications, found in Appendix A of the Guidelines, with the United States Geological Survey (USGS) Lidar Guidelines and Base Specifications v13 so that data procured and used by the Federal government is consistent across agencies and is updated to industry standards.

DDSM;-)

I've found the local flood plane managers to be very efficient at calculating BFEs. They use the FEMA computer model and local knowledge of roads and drainage patterns, outfall canal capacity, soil types, etc ... As said above, determining the BFE to FEMA's satisfaction is a challenge.

Once, I submitted a LOMA in a zone AE with a BFE posted on the map. If you read the map, it says when the BFE is noted like this: (el 12) under the Zone label then 12' is a uniform BFE for the entire zone, so I put 12' as the BFE. For some reason, FEMA changed it to 12.2', or some such thing. It didn't matter, but I can't understand how the maps can say 'uniform BFE for the zone' but FEMA can come up with something different. My only guess is that the guy reviewing the LOMA wanted to put his mark on it somehow.

You can submit a LOMA with your best determination as to the BFE. FEMA will then check their own data to see if you have done it correctly. They will tell you, either way, if they disagree with your value. I know this because I've had them do this several times. In one case, the came up with a number nearly seven feet lower than what the Zone A on the FHBM would suggest. In another case, we differed by only 0.2 feet, but, that was enough to keep the house in the flood plain.