Determining a BFE for a property is normally straight forward using the FIS but I've run into a situation where one of the FIS cross sections is quite skewed to the centerline of the creek on the FIRM. It is also quite skewed to the BFE 1' marks. (Imagine the "not equal to" sign)
In nearly all situations, I can estimate perpendicular to the creek/river centerline and work my way along the FIS to get the BFE. Even if the centerline wanders, I can proportionally estimate and get quite close. We also always use the upstream side of the area where the building will go just to be on the safe side.
If we use the perpendicular method, our BFE based on the FIS is lower than the downstream 1' BFE on the FIRM. If we use a "radial" proportionate method through the curve of the creek and the skewed FEMA cross section, it puts us quite a bit above the downstream 1' FIRM BFE but we are very close to that line.
We don't want the builder to have a house that sits 3' above the existing ground if its not needed.
Anyone have any suggestions?
Man did I ramble on that one.....:pinch:
I let the Floodplain Administrator determine all the BFE's on certificates and furnish the info to me in a letter. I do verify.
> I let the Floodplain Administrator determine all the BFE's on certificates and furnish the info to me in a letter. I do verify.
Good idea, up where I work in Idaho there are hardly any administrators and the ones that are shouldn't be. In similar instances we had to hire one of those hydrlogists to analyze things based on our topo data. It was surprisingly inexpensive and worked well.