Floodplain Requirements for Fill, Grading, Excavation, & Crossing Structures
Applicant discusses the project with the Floodplain Coordinator and the requirements for the permit are given.
In areas where flood elevations are unknown (unnumbered “A” Zones), the applicant’s engineer must show that the fill, bridge or culvert will not increase the BFE by more than one (1) foot at any point.
In areas where the flood elevation is known (numbered “A” and “AE” Zones) but floodway is not designated, the applicant’s engineer must show that the fill, bridge or culvert will not increase the BFE by more than one-tenth (1/10th) of a foot at any point.
In both cases above, adjacent properties must not be impacted without the owner’s permission.
For areas where flood elevations are known (numbered “A” and “AE” Zones) and a floodway is designated, filling in a floodplain requires the applicant’s engineer to show that the fill will not increase the BFE. For crossing structures, bridges must span the floodplain or the applicant’s engineer must show that it is stable during 100-year flood flows/velocities and does not increase the BFE. Culverts need to be designed by an engineer to pass the 100-year flood flows without increasing the BFE. A bond is taken to ensure the structure or grading/fill/excavation is built according to the plans. If excavation is planned, the requirement is generally to remove the spoil (excavated) material from the floodplain to an upland location.