Floodplain Determination Methodology

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Community officials use the Flood Insurance Rate Maps (FIRM) to administer floodplain management regulations per minimum National Flood Insurance Program (NFIP) standards and adopted local ordinances. Once a request has been made to the Stormwater Management Division to determine the zone designation for a specific property, the following steps are taken:

Step 1. Identify the correct FIRM Panel.

Step 2. Determine the general location of the property. Only major roads and the roads in or near flood-prone areas are shown on the FIRM. Therefore, alternative sources such as Geographic Information Systems (GIS) are used.

Step 3. Determine the specific location of the property by using the FIRM map scale.

Step 4. Determine the flood insurance zone designation for the property.


FEMA (Federal Emergency Management Agency) Floodzone Designations

A
-- This identifies an area inundated by 100-year flooding for which no base flood elevation (BFE) has been determined.

AE -- This identifies an area inundated by 100-year flooding for which BFE has been determined.

X -- This identifies an area that is determined to be outside the 100- and 500-year floodplains.

X500 -- This identifies an area inundated by 500-year flooding; an area inundated by 100-year flooding with average depths of less than one foot or with drainage areas less than one square mile; or an area protected by levees from 100-year flooding.
 

References:
FEMA (1998) "Guide to Flood Insurance Maps". FIA-14
FEMA "FIRM" Retrieved from FEMA Web site on December 16, 2003