We have been asked to prepare an EC for a proposed building that is in a Zone X adjacent to an AE Zone, however the ground elevation of the Zone X is about 2 feet below the BFE for the Zone AE. My question is: In B9 do we show the BFE for the adjacent AE Zone? The proposed building is graphically outside the AE Zone.
TIA
Ed Killough, NCPLS
Strange
Is there a large mound or hill between your lot and Zone AE? In some places, I suppose, you could be below a base flood elevation and not be threatened by the flood hazard zone.
If the proposed structure is clearly in Zone X there should be no need for an elevation certificate. You could still fill one out though putting Zone “X” in B8, and “Not Applicable” in B9. Then in section D (comments) insert comments to the effect that parcel/structure is in Zone X and therefore does not require a BFE. B-)
Strange
No mound, the AE Zone runs through the lot. The lot is flat and the entire lot is below the BFE.
Thanks, that is what I was thinking, just wanted to see what others thought.
Ask your community flood official.
be really careful with this one!!
I have one Zone A where almost the entire Zone A is above the flood plain, don't automatically trust the BFE's.
Not so strange
Button pushers
GIS masters
Drafters
Idiots who allow the computer to tell them the answer
If this is a modern FIRM then I believe I know what it is. In ARC you can take a geotiff (a grid) and increase the cell size (decrease the resolution). The purpose is to setup your routine and make sure that it works.
Then you go back and change your geotiff resolution back to the fine 1 meter grid. Let the computer run the calcs all night long and determine the limits of your flood hazard zones.
What happens if the GIS Master who determined the flood zone did not refine the resolution and thus the solution??? You get the POS maps that we have. I have seen flood plains differ by over 150' with the new modern maps. Usually they are uphill of the actual elevation though, so to have one downhill makes me ask more questions.
At the time of the lidar 'survey' was the lot heavily wooded with a thick underbrush? Do you think the fine folks processing the lidar data may have used vegetation and not actual ground? You can go so far as to get the lidar data and compare. I have a workflow written out using QGIS (free) to convert geotiffs to SHP contours that I would be happy to share.
In your case, I would assume that the flood plain extends to the contour, just like with the old maps.
Not so strange
Most of the lot is mowed grass lawn and the map is from 1999.
Not so strange
Oh
What does the FIS state?
Is this inland?
I reviewed a coastal flood zone with the flood plain manager for the state. It was an AE elev 15 with a Shaded X behind it. The ground in the Shaded X is at elevation 14. Rich described the bizarre methods of flood plain mapping. They will not plot every zone (which is why we don't see every foot represented). So in my case, the end of the AE 15 was actually around elevation 12.
What aerial did they rely on in 1999? We had maps revised in 1998 that were based on a 1977 or 1979 aerial that was off by feet in many areas.
Not so strange
I have not found out yet what aerial was used for this mapping, but sound similar to you case. The AE is showing an elevation of 23 and all the surrounding natural ground is at elevation 21. It is approximately one mile inland, but the flood plane is not coming from the ocean side.
> My question is: In B9 do we show the BFE for the adjacent AE Zone? The proposed building is graphically outside the AE Zone.
I really can't believe some of the above comments.
okay, so in a 100 year flood, is the water going to stop at FEMAS graphically/horizontally depicted zone X/AE line. No it is going to extend (at a min.) to the base flood elev. as depicted in the FIS profiles regardless of where FEMA shows the division line graphically.
Your site is in the AE zone (based upon elevation) and should be reported as such. It is not the horizontal location that determines compliance it is the vertical.
Think of this another way, when and if the house floods do you want your elev. cert to say you determined the property to not flood because it is shown graphically in an X zone or would you rather have it say zone AE with appropriate elevations.
Have you checked the FIS profiles?
Jim
The written policy of FEMA is that horizontal geographic coordinates control the determination of Special Flood Hazard Boundaries. The exception is where the FIRM panel has no grid ticks or coordinates shown. This policy was developed to provide a consistent method of rating for insurance purposes. In fact, the entire program is for the administration of insurance and aid.
The panels and profiles will not prevent flooding unless you print them on a levy. The proper course is to show the structure in Zone 'X' and note that it is lower than the adjacent BFE in the comments section. Advise the client to insure the structure and thank his lucky stars for the preferred rate.
In the event you have a community flood program and/or manager you should inform them of your findings. The community will need to address the issue or risk losing their rating.
In a perfect world our certificates would evaluate risk. They don't, and they were never designed too.
My .02, Tom
“Think of this another way, when and if the house floods do you want your elev. cert to say you determined the property to not flood because it is shown graphically in an X zone ……..”
From a business standpoint, absolutely yes. B1 through B8 sufficiently illustrate the information utilized in arriving at the conclusions stated. Again, from a business standpoint, I don’t feel it’s my responsibility to argue with FEMA as to the accuracy of their maps.
Just say’in…..B-)
>Advise the client to insure the structure and thank his lucky stars for the preferred rate.
Okay i'll bite. Elev cert says he is in zone x graphically. LAG on the elev cert says two feet lower than BFE. Bank now wants a loma, how long before FEMA kicks that one back
> In a perfect world our certificates would evaluate risk. They don't, and they were never designed too.
Well I kind of always thought that the premiums were based upon building elevations.
Knowing the elevations helps evaluate risk.
Jim
I have had this happen. FEMA issued the LOMA. The structure was in Zone X. There is no BFE in zone x. The elevation of the structure would impact the premium if it were in a SFHA. Same answer, there is no BFE in zone x...
