The National Flood Insurance Act of 1968, as amended in 1973, provides for a federally subsidized National Flood Insurance Program (NFIP) conditioned on active management and regulation of floodplain development by states and local governments. FEMA administers the NFIP as a part of its overall responsibilities in preventing and responding to natural events that damage private and public property and any life-threatening natural event including floods. The NFIP provides flood insurance at affordable rates through Federal subsidy of the insurance offered by licensed insurance agents. This insurance is designed to provide an insurance alternative to disaster assistance to meet the escalating costs of repairing damage to buildings and their contents caused by floods.

Participation in the NFIP is based on an agreement between local communities and the Federal Government. This agreement states if a community will adopt and enforce a floodplain management ordinance to reduce future flood risks to new construction in Special Flood Hazard Areas, the Federal Government will make flood insurance available within the community as a financial protection against flood losses.

Availability of the subsidized flood insurance is contingent upon the development of a floodplain management system by the local municipality. Prevention of floods and resultant property damage is achieved through the delineation of property subject to flood events and the establishment of specific rules concerning development within these designated areas. FEMA publishes Flood Insurance Rate Maps (FIRM’s) for certain flood prone areas that delineate different special flood hazard areas.

National Flood Insurance is available in more than 19,000 communities across the United States. Phoenix has participated in NFIP since l979 and has adopted the standard NFIP requirements. The city of Phoenix standards require that residential buildings located in a SFHA be elevated to one foot above the base flood elevation (BFE), which is defined as the elevation of the flood that has a 1% chance of occurring in any given year (also called the 100-year flood). In addition, development may only fill or otherwise develop within this 100-year floodplain to the extent that the water surface elevation of the 100-year flood is raised no more than one foot within the floodplain adjacent to the proposed project. The combination of these two requirements protects buildings from a 100-year flood and any increase in the 100-year flood caused by the project.

Glossary of Terms

Flood Hazard Zones

The flood hazard maps are subdivided into zones that relate to flooding depths. These are defined as follows:

Zone A: No base flood elevations determined.

Zone AE: Base flood elevations determined.

Zone AH: Flood depths of 1 to 3 feet (usually areas of ponding), base flood elevations determined.

Zone AO: Flood depths of 1 to 3 feet (usually sheet flow on sloping terrain), average depths determined (and velocities determined for alluvial fan floodplains).

Zone X (shaded): Areas of 500-year flood; areas of 100-year flood with average depths of less than 1 foot or with drainage areas less than 1 square mile; and areas protected by levees from 100-year flood.

Zone X (unshaded): Areas determined to be outside 500-year floodplain.

Base Flood- means the flood having a one percent chance of being equaled or exceeded in any given year, i.e., the one-hundred-year flood.

Floodplain- means the relatively flat area adjoining the channel of a watercourse, or areas where drainage is or may be restricted by natural or manmade structures which may have been or may be covered partially or wholly by floodwater from a base flood.

100-year Floodplain: Floodplain resulting from the occurrence of the 100-year rainfall. FEMA sets its jurisdictional limits to the 100-year event, which is cited as the base flood elevation. Jurisdictional limits are defined by horizontal flooding limits using the base flood elevation

Floodway: That portion of the 100-year floodplain that is required to convey the 100-year flood with a rise in water surface no greater than 1 foot. The allowable rise and the limits of the floodway are predetermined by the governing municipality. The city of Phoenix allows landowners to encroach into the 100-year floodplain equally on both sides in terms of conveyance, except where a Flood Hazard and Erosion Management District has been adopted.

Floodway Fringe Area- means that portion of the area of special flood hazard that is not included in the selected floodway.

Encroachment-means any man-made obstruction in the floodplain which displaces the natural passage of flood waters.

Surcharge- means an increase in flood elevation due to destruction of the floodplain that reduces its conveyance capacity.

Last modified on 07/02/2007 14:33:24