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<br />A FIRM depicts 100- and SOD-year floodplain
<br />boundaries, flood insurance rate zones, BFEs,
<br />base flood depths, and, occasionally, 100-year
<br />floodway boundaries, The FIS report describes
<br />the analyses performed for the FIS and provides
<br />tables and figures that present the study results,
<br />
<br />The information presented on a FIRM and in an
<br />FIS report is usually the result of detailed
<br />engineering analyses performed as part of an
<br />FIS, Those analyses i ncl ude hydrologic analyses
<br />that yield flood discharge-frequency
<br />relationships and hydraulic analyses that yield
<br />computed flood elevations and depths, The
<br />hydrologic analyses usually involve the use of
<br />statistical analyses of recorded stream gage
<br />data, regional discharge-drainage area
<br />relationships, or rainfall-runoff models,
<br />
<br />For riverine flooding sources, the hydraulic
<br />analyses usually involve backwater
<br />computations or other hydraulic computations
<br />that are based on the computed flood
<br />discharges and the results of field surveys,
<br />Special techniques are used for the analysis of
<br />(Castal floodin9, a\lu~ial {an {loodin9, and ic~
<br />jams,
<br />
<br />SFHAs identified through the use of detailed
<br />engineering analyses are assigned "detailed"
<br />zone designations (Zone AO, Zone AH, Zones
<br />A1-A30 or Zone AE, Zones Vl-V30 or Zone VEl, A
<br />FIRM may also depict approximate SFHAs, which
<br />may have been taken directly from an effective
<br />FHBM or developed by the FIS Contractor using
<br />approximate engineering analyses,
<br />
<br />The 100- and SOD-year floodplain and 100-year
<br />floodway boundaries may be shown on a
<br />separate Flood Boundary and Floodway Map
<br />(FBFM) published as an exhibit in the FIS report,
<br />For most recent FISs, FBFMs are not prepared,
<br />and all flood risk information, including
<br />information related to the 1 DO-year floodway, is
<br />shown on the FIRM,
<br />
<br />Occasionally, an entire FIRM is created directly
<br />from an FHBM; no detailed engineering
<br />analyses are performed, Such a FIRM does not
<br />present the detailed flood risk information
<br />usually shown on FIRMs, but it does enable the
<br />mapped community to participate in the
<br />Regular Phase of the N FIP,
<br />
<br />Additional information about the various types
<br />of FIRMs now in effect is provided in a separate
<br />FEMA publication, Guide to Flood Insurance
<br />Rate Maps, which describes the key elements of
<br />FIRMs and explains how to use a FIRM, See
<br />Appendix C for information about how to
<br />obtain copies of Guide to Flood Insurance Rate
<br />Maps and other FEMA publications,
<br />
<br />Before entering the Emergency and Regular
<br />Phases of the NFIP, the community must, if it has
<br />not already done so, adopt and enforce
<br />floodplain management regulations that are
<br />aimed at reducing future flood losses and that
<br />meet the minimum standards ofthe NFIP,
<br />
<br />Need for Documentation
<br />
<br />The flood risk information presented on NFIP
<br />maps and in FIS reports forms the technical basis
<br />for the administration of the NFIP, Participating
<br />communities use the information to develop the
<br />floodplain management ordinances required
<br />under the NFIP, and FEMA uses the information
<br />to establish actuarial rates for flood insurance,
<br />Because of the importance of that information,
<br />FEMA exercises great care to ensure that the
<br />analytical methods employed in FISs are
<br />scientifically and technically correct, that the
<br />engineering procedures followed meet
<br />professional standards, and, ultimately, that the
<br />results ofthe FIS are accurate,
<br />
<br />Although NFIP maps and FIS reports are
<br />prepared according to rigorous technical
<br />standards, FEMA recognizes that improvements
<br />in the techniques used in assessing flood risks,
<br />changes in physical conditions in floodplains or
<br />watersheds, and the availability of new scientific
<br />or technical data may necessitate changes to the
<br />maps am! r~ports, In addition, the limitations
<br />imposed by the scales at which the maps are
<br />prepared may result in individual properties
<br />being inadvertently included in SFHAs,
<br />
<br />Therefore, the NFIP regulations allow FEMA to
<br />revise and amend NFIP maps and FIS reports, as
<br />warranted, at its discretion or after it receives
<br />requests from community officials and
<br />individual property owners, Indeed, to help
<br />FEMA ensure that the maps and reports present
<br />information that accurately reflects existing
<br />flood risks, the NFIP regulations (Section 6S,3)
<br />
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