Freeboard in Zone V and Coastal Zone A Areas
John Ingargiola, FEMA Mitigation Directorate
"Freeboard" is a term used in floodplain management as a factor of safety, usually expressed in feet above a flood level. Freeboard tends to compensate for the many unknown factors that could contribute to flood heights greater than the height calculated for a selected size flood and floodway conditions, such as wave action, bridge openings, and the hydrological effect of urbanization of the watershed.
Freeboard is not required by NFIP standards, but communities are encouraged to adopt at least a 1-foot freeboard to account for the 1-foot rise built into the concept of designating a floodway and the encroachment requirements where floodways have not been designated. Freeboard results in significantly lower flood insurance rates due to lower flood risk.
Freeboard will be included in the 2009 International Residential Codes for One- and Two-Family Dwellings. This comprehensive code establishes minimum requirements for one- and two-family dwellings of three stories or less. It brings together all building, plumbing, mechanical, fuel gas, energy, and electrical provisions for one- and two-family residences. This Code is updated every three years. A fact sheet produced by the International Code Council provides more information about the Codes.
It is significant for freeboard to be included in the next edition of the codes; however, it will be required only in Zone V and Coastal Zone A (where such zones are designated) areas.
The Association of State Floodplain Managers and several State floodplain associations actively supported the FEMA proposal to incorporate freeboard into the new code, and their support was evident at the recent code change hearings in Minneapolis, Minnesota. The original proposal to include freeboard standards in all Special Flood Hazard Areas needed support from two-thirds of the eligible voting attendees to become effective and it received 63.5 percent of the votes. This close vote signals growing support for a measure floodplain managers have long recognized as highly effective in reducing flood damage.
The flood damage reduction benefits of freeboard and the savings on NFIP flood insurance policies were documented in the NFIP Evaluation Report, Evaluation of the National Flood Insurance Program's Building Standards (October 2006). The savings are especially significant in Zone V areas, where the incremental cost of elevating above the Base Flood Elevation can be recovered through lower insurance premiums in just a few years.
At the Minneapolis code hearings, the National Association of Home Builders supported freeboard in Zone V and Coastal Zone A areas, a turnaround from its previous position opposing all freeboard requirements. The evidence of the benefits of freeboard in Zone V and Coastal Zone A areas made the difference, although the organization continues to be cautious about the added cost of freeboard in areas where fill is used.
John Ingargiola is a Senior Engineer in the Building Science Branch of the FEMA Mitigation Directorate.