The Flood Insurance Rate Map (FIRM) is a tool developed by, or under contract to, the Federal Emergency Management Agency (FEMA) to rate flood insurance policies sold through the National Flood Insurance Program (NFIP).
The FIRM is a pictorial representation of the results of hydrologic studies and historical flood and weather experience. In these studies, engineers determine how high water might rise and how often it could reach that height. For the FIRM, they select the water surface elevation that has a 1% chance of occurring in any year and compare it with the ground elevation. That water surface elevation is called the Base Flood level. When the water is predicted to reach, for example, 50 feet Mean Sea Level (MSL) in a certain area and the ground in that area is lower than 50 feet MSL, then the ground would be covered by water. The area where the ground would be covered by water in a base flood is said to be in the Special Flood Hazard Area (SFHA).
The zone designations for SFHAs begin with A or V. The 1% annual chance flood, or base flood, is commonly referred to as the 100-year flood. If you would like to know more about the various As and Vs, look on the printed FIRM. FEMA provides an online explanation of flood maps and answers to questions on the FEMA mapping page for homeowners.
When property is determined to be in the SFHA, there is a reasonable expectation that something built on the property below the expected flood level will have a 1% or higher chance of being inundated by floodwater. One percent is five times the "acceptable" risk of fire and accumulates to a 26% chance of flooding over the 30-year mortgage period. That is why, for buildings in the SFHA, the federal government mandates that mortgages secured by buildings in the SFHA be protected by flood insurance on those buildings.
ABFEs and other more protective maps and regulations
Some communities adopt maps and regulations that:
The advisory guidance and maps produced following a disaster fall into this category. To some extent they are an estimate of what the new FIRM will look like. (FIRMS take 18 months to 2 years to produce.) Following hurricanes Katrina and Rita, the federal government dictated that rebuilding financed with federal funds would have to use the advisory BFEs. The Louisiana Recovery Authority went a step further, dictating that only those communities that adopt the advisory BFEs (and apply them to all restoration, even restoration that is funded by the community or property owners) could receive Hazard Mitigation Grant Program funds. Some communities chose not to adopt the ABFEs.
Insurance rates are always based on the FIRM, even when building regulations are based on more-restrictive maps and ordinances.
Finding the Official Flood Map (FIRM)
Your local permit, building or flood office is the official source of flood risk information in your community. The FIRM is the principal risk-determination tool; following a major disaster, the advisory maps and guidance are a better source of flood risk information, even if it has not been adopted for regulatory purposes. The local floodplain administrator has regulatory authority in flood hazard areas and, in some communities, outside flood hazard areas.
Insurance and real estate agents often have access to copies of the flood maps for the communities in which they do business, and maps are sometimes available in public libraries. Only the local government office is required to keep records of map revisions and amendments that have occurred since the maps were printed. The community building or permit office will know who the floodplain administrator is in your community.
Find the local floodplain administrator in your parish here.
Finding Your Property on the FIRM
The LSU AgCenter Flood Maps portal, created during the Road Home program, provides interactive access to current, future, pending and most recent historical maps. These maps also provide Basic Wind Speed (for the building code) and ground elevation data for the point chosen.
FEMA provides an online service that allows you to locate your property on the FIRM as the map was printed (without revisions and amendments that have been made since the map was printed). Finding your property is easy if you have a recognizable address. If you don't, you can use a point-and-click method to zoom in on the map and point to your property.
A number of Flood Map Determination companies in the country will determine whether a property is in the SFHA or not. These fee-based services are often used by mortgage companies to decide whether they must require flood insurance on the buildings securing their mortgage. FEMA's index of map determination companies.
Regulations in Special Flood Hazard Areas
The FIRM is adopted by parish and local governments as a regulatory tool. Some communities adopt regulatory maps that include flood hazards that are more extensive than those shown on the FIRM.
For properties in the SFHA and in flood hazard areas recognized by the community, certain regulations (building, remodeling and restoration) apply. These regulations may not apply to development in areas outside the SFHA.
About one-fourth of the flood insurance claims paid by the National Flood Insurance Program (NFIP) are for properties NOT in the SFHA. The official map determination is not a definitive determination of flood risk. It would be wise to check with the local floodplain administrator, building office or public works department.
Below is a sampling of the types of activities that are regulated in the SFHA:
New homes must be built so the lowest floor is above the flood hazard (above BFE or adopted ABFE) or higher in some communities.
New non-residential buildings must meet this standard or be floodproofed.
New and existing buildings, if securing a federally guaranteed mortgage or a mortgage from a federally insured institution, must carry flood insurance.
Extensive renovation, improvement or repair of existing buildings must comply with the elevation requirement for new construction. "Extensive" usually means the cost to repair (or remodel) is 50% or more of the pre-damaged value (or value before remodeling).
Development permits must be obtained for all construction, improvement and other development (drainage improvement, laying infrastructure, stockpiling).