[Code of Federal Regulations]
[Title 44, Volume 1]
[Revised as of October 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 44CFR65.6]

[Page 341-344]
 
              TITLE 44--EMERGENCY MANAGEMENT AND ASSISTANCE
 
             CHAPTER I--FEDERAL EMERGENCY MANAGEMENT AGENCY
 
PART 65--IDENTIFICATION AND MAPPING OF SPECIAL HAZARD AREAS--Table of Contents
 
Sec. 65.6  Revision of base flood elevation determinations.

    (a) General conditions and data requirements. (1) The supporting 
data must include all the information FEMA needs to review and evaluate 
the request. This may involve the requestor's performing new hydrologic 
and hydraulic analysis and delineation of new flood plain boundaries and 
floodways, as necessary.
    (2) To avoid discontinuities between the revised and unrevised flood 
data, the necessary hydrologic and hydraulic analyses submitted by the 
map revision requestor must be extensive enough to ensure that a logical 
transition can be shown between the revised flood elevations, flood 
plain boundaries, and floodways and those developed previously for areas 
not affected by the revision. Unless it is demonstrated that it would 
not be appropriate, the revised and unrevised base flood elevations must 
match within one-half foot where such transitions occur.
    (3) Revisions cannot be made based on the effects of proposed 
projects or

[[Page 342]]

future conditions. Section 65.8 of this subchapter contains provisions 
for obtaining conditional approval of proposed projects that may effect 
map changes when they are completed.
    (4) The datum and date of releveling of benchmarks, if any, to which 
the elevations are referenced must be indicated.
    (5) Maps will not be revised when discharges change as a result of 
the use of an alternative methodology or data for computing flood 
discharges unless the change is statistically significant as measured by 
a confidence limits analysis of the new discharge estimates.
    (6) Any computer program used to perform hydrologic or hydraulic 
analyses in support of a flood insurance map revision must meet all of 
the following criteria:
    (i) It must have been reviewed and accepted by a governmental agency 
responsible for the implementation of programs for flood control and/or 
the regulation of flood plain lands. For computer programs adopted by 
non-Federal agencies, certification by a responsible agency official 
must be provided which states that the program has been reviewed, 
tested, and accepted by that agency for purposes of design of flood 
control structures or flood plain land use regulation.
    (ii) It must be well-documented including source codes and user's 
manuals.
    (iii) It must be available to FEMA and all present and future 
parties impacted by flood insurance mapping developed or amended through 
the use of the program. For programs not generally available from a 
Federal agency, the source code and user's manuals must be sent to FEMA 
free of charge, with fully-documented permission from the owner that 
FEMA may release the code and user's manuals to such impacted parties.
    (7) A revised hydrologic analysis for flooding sources with 
established base flood elevations must include evaluation of the same 
recurrence interval(s) studied in the effective FIS, such as the 10-, 
50-, 100-, and 500-year flood discharges.
    (8) A revised hydraulic analysis for a flooding source with 
established base flood elevations must include evaluation of the same 
recurrence interval(s) studied in the effective FIS, such as the 10-, 
50-, 100-, and 500-year flood elevations, and of the floodway. Unless 
the basis of the request is the use of an alternative hydraulic 
methodology or the requestor can demonstrate that the data of the 
original hydraulic computer model is unavailable or its use is 
inappropriate, the analysis shall be made using the same hydraulic 
computer model used to develop the base flood elevations shown on the 
effective Flood Insurance Rate Map and updated to show present 
conditions in the flood plain. Copies of the input and output data from 
the original and revised hydraulic analyses shall be submitted.
    (9) A hydrologic or hydraulic analysis for a flooding source without 
established base flood elevations may be performed for only the 100-year 
flood.
    (10) A revision of flood plain delineations based on topographic 
changes must demonstrate that any topographic changes have not resulted 
in a floodway encroachment.
    (11) Delineations of flood plain boundaries for a flooding source 
with established base flood elevations must provide both the 100- and 
500-year flood plain boundaries. For flooding sources without 
established base flood elevations, only 100-year flood plain boundaries 
need be submitted. These boundaries should be shown on a topographic map 
of suitable scale and contour interval.
    (12) If a community or other party seeks recognition from FEMA, on 
its FHBM or FIRM, that an altered or relocated portion of a watercourse 
provides protection from, or mitigates potential hazards of, the base 
flood, the Administrator may request specific documentation from the 
community certifying that, and describing how, the provisions of 
Sec. 60.3(b)(7) of this subchapter will be met for the particular 
watercourse involved. This documentation, which may be in the form of a 
written statement from the Community Chief Executive Officer, an 
ordinance, or other legislative action, shall describe the nature of the 
maintenance activities to be performed, the frequency with which they 
will be performed, and the title of the local community official who 
will be responsible

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for assuring that the maintenance activities are accomplished.
    (13) Notwithstanding any other provisions of Sec. 65.6, a community 
may submit, in lieu of the documentation specified in Sec. 65.6(a)(12), 
certification by a registered professional engineer that the project has 
been designed to retain its flood carrying capacity without periodic 
maintenance.
    (14) The participating community must provide written assurance that 
they have complied with the appropriate minimum floodplain management 
requirements under Sec. 60.3 of this chapter. This includes the 
requirements that:
    (i) Existing residential structures built in the SFHA have their 
lowest floor elevated to or above the base flood;
    (ii) The participating community has determined that the land and 
any existing or proposed structures to be removed from the SFHA are 
``reasonably safe from flooding,'' and that they have on file, available 
upon request by FEMA, all supporting analyses and documentation used to 
make that determination;
    (iii) The participating community has issued permits for all 
existing and proposed construction or other development; and
    (iv) All necessary permits have been received from those 
governmental agencies where approval is required by Federal, State, or 
local law.
    (15) If the community cannot assure that it has complied with the 
appropriate minimum floodplain management requirements under Sec. 60.3, 
of this chapter the map revision request will be deferred until the 
community remedies all violations to the maximum extent possible through 
coordination with FEMA. Once the remedies are in place, and the 
community assures that the land and structures are ``reasonably safe 
from flooding,'' we will process a revision to the SFHA using the 
criteria set forth under Sec. 65.6. The community must maintain on file, 
and make available upon request by FEMA, all supporting analyses and 
documentation used in determining that the land or structures are 
``reasonably safe from flooding.''
    (b) Data requirements for correcting map errors. To correct errors 
in the original flood analysis, technical data submissions shall include 
the following:
    (1) Data identifying mathematical errors.
    (2) Data identifying measurement errors and providing correct 
measurements.
    (c) Data requirements for changed physical conditions. Revisions 
based on the effects of physical changes that have occurred in the flood 
plain shall include:
    (1) Changes affecting hydrologic conditions. The following data must 
be submitted:
    (i) General description of the changes (e.g., dam, diversion 
channel, or detention basin).
    (ii) Construction plans for as-built conditions, if applicable.
    (iii) New hydrologic analysis accounting for the effects of the 
changes.
    (iv) New hydraulic analysis and profiles using the new flood 
discharge values resulting from the hydrologic analysis.
    (v) Revised delineations of the flood plain boundaries and floodway.
    (2) Changes affecting hydraulic conditions. The following data shall 
be submitted:
    (i) General description of the changes (e.g., channelization or new 
bridge, culvert, or levee).
    (ii) Construction plans for as-built conditions.
    (iii) New hydraulic analysis and flood elevation profiles accounting 
for the effects of the changes and using the original flood discharge 
values upon which the original map is based.
    (iv) Revised delineations of the flood plain boundaries and 
floodway.
    (3) Changes involving topographic conditions. The following data 
shall be submitted:
    (i) General description of the changes (e.g., grading or filling).
    (ii) New topographic information, such as spot elevations, cross 
sections grading plans, or contour maps.
    (iii) Revised delineations of the flood plain boundaries and, if 
necessary, floodway.
    (d) Data requirements for incorporating improved data. Requests for 
revisions

[[Page 344]]

based on the use of improved hydrologic, hydraulic, or topographic data 
shall include the following data:
    (1) Data that are believed to be better than those used in the 
original analysis (such as additional years of stream gage data).
    (2) Documentation of the source of the data.
    (3) Explanation as to why the use of the new data will improve the 
results of the original analysis.
    (4) Revised hydrologic analysis where hydrologic data are being 
incorporated.
    (5) Revised hydraulic analysis and flood elevation profiles where 
new hydrologic or hydraulic data are being incorporated.
    (6) Revised delineations of the flood plain boundaries and floodway 
where new hydrologic, hydraulic, or topographic data are being 
incorporated.
    (e) Data requirements for incorporating improved methods. Requests 
for revisions based on the use of improved hydrologic or hydraulic 
methodology shall include the following data:
    (1) New hydrologic analysis when an alternative hydrologic 
methodology is being proposed.
    (2) New hydraulic analysis and flood elevation profiles when an 
alternative hyrologic or hydraulic methodology is being proposed.
    (3) Explanation as to why the alternative methodologies are superior 
to the original methodologies.
    (4) Revised delineations of the flood plain boundaries and floodway 
based on the new analysis(es).
    (f) Certification requirements. All analysis and data submitted by 
the requester shall be certified by a registered professional engineer 
or licensed land surveyor, as appropriate, subject to the definition of 
``certification'' given at Sec. 65.2 of this subchapter.
    (g) Submission procedures. All requests shall be submitted to the 
FEMA Regional Office servicing the community's geographic area or to the 
FEMA Headquarters Office in Washington, DC, and shall be accompanied by 
the appropriate payment, in accordance with 44 CFR part 72.

[51 FR 30314, Aug. 25, 1986, as amended at 53 FR 16279, May 6, 1988; 54 
FR 33550, Aug. 15, 1989; 61 FR 46331, Aug. 30, 1996; 62 FR 5736, Feb. 6, 
1997; 66 FR 22442, May 4, 2001]