Standard practice is for a land surveyor to fill out the building and land elevation portion of the certificate and submit it to a separate party, such as FEMA, to complete the 100-year base flood elevation (BFE), if the BFE is not provided in FEMA documentation. The BFE will then be determined by overlaying the flood zone contours on a topographic map. This method is inherently inaccurate, as flood zone contours without a stated BFE act as placeholders and do not represent the actual flooding conditions that may occur. A large number of these flood zones were hand drawn in a GIS program using outdated information and do not align with the natural terrain contours expected from a flooding event.

 

This is illustrated in the example photo below. The building structure in question is represented by the yellow dot. The red line represents FEMA's BFE contour, and the transparent shading represents the derived BFE from hydrologic modeling. As one can see, the FEMA BFE (red line) does not match the natural terrain profile and inconsistently jumps between 1' elevation contours (black lines). For this example property, it was determined the building structure does not reside in Flood Zone A. A letter of map amendment (LOMA) was submitted to FEMA and the subject building was removed out of the flood zone, saving the owner over $25,000 in flood insurance cost over the next 30 years. This would have not been the case if FEMA's BFE was used.