Within the Special Flood Hazard Area, FEMA has designated Regulatory Floodways along some rivers, creeks or other water channels. FEMA regulates filling and construction in floodways to allow flood waters to be discharged without raising surface water levels beyond a designated height. Inclusion in a regulatory floodway does not specifically impact flood insurance rates, but it does affect construction regulations. 


All permits issued in the regulatory floodway must be reviewed for their impact on the floodway. Filling and construction may be permitted only in these circumstances:

  • FEMA No-Rise (No-Impact) Certification – A licensed professional engineer (PE) may certify that the fill and/or No-Impact Certification Guideconstruction will not cause the floodway to rise. 
    • A narrative format may be used for certain minor projects, especially where the construction site is at or above the base flood elevation or in the shadow of an existing conveyance.
    • Hydraulics modeling must be submitted for all other projects. Currently for unincorporated Lee County, the HEC-RAS model is used.
    • Minor project waiver – Lee County may waive the requirement for minor projects, where the impact on the floodway is clearly negligible and the cost of engineering would exceed the cost of the project. 
  • Parcel owners may also apply directly to FEMA to change the boundaries of the regulatory floodway. Options for Letters of Map Change include:
    • Letter of Map Amendment (LOMA) – If the parcel is higher than the base flood elevation, FEMA may amend the zone for that parcel and place it in the X Zone. 
    • Letter of Map Revision – A professional engineer may submit certified, updated hydraulics and/or hydrology modeling to show that the parcel should not be included in the regulatory floodway.
    • Conditional Letter of Map Revision – A professional engineer may submit certified, updated hydraulics and/or hydrology modeling to show that proposed construction can be accomplished to eliminate any rise in the floodway. This often requires construction of drainage areas, culverts or other drainage systems and preserved open space on the site.
    • Lee County's Guide to No-Rise (No Impact) Certification - For applications to FEMA for letters of Map Revision based on Fill (LOMR-F) in a regulatory floodway, the process will be reviewed under the MT-2 process (not the MT-1 process).


Regulatory Floodway Quick Links:


Learn more about these Flood Zone topics: