FIRM-920618MEMO FILE COPY
TO: Frank Trando, Finance Director
FROM: Kenneth M. Griffin, P.E.: City Engineer
SUBJECT: - Floodplain Management Ordinance Review/Revisions to the Flood
_Lnsurar�ce Rate Maps (FIRM) and Flood Insurance Study (FIS)
RE: City Council work Session /June 23, 1992
DATE: June 18, 1992
During the above referenced work session, Staff will make a presentation
on the Floodplain Management Ordinance. in particularly, the presentation
will focus on giving a clear understanding of the one - hundred year storm,
floodplain, floodway, floodplain management area, floodplain development
permit and valid reasons for variances to the requirements of the
ordinance.
Our current Flood Insurance Rate Maps are dated October 16, 1991.
However, since December 1991, the City has had revised maps under review.
A report from the City was submitted to FEMA on June 8, 1992. Some time
this summer the City will be adopting the new maps.
If City Council provides direction on any changes to the ordinance, based
on the presentation, then those changes could be evaluated and
incorporated into the new Floodplain Management Ordinance when the revised
maps are adopted.
If you should have any questions, please let me know.
KMG /bd
FMOAGI
100-YEAR FLOOD PLAIN
FLOOD FRINGE FLOODWAY ]I- - FLOOD
STREAM FRINGE
CHANNEL
FLOOD ELEVATION WHEN
CONFINED WITHIN FLOOD Y
ENCROACHMENT
ENCROACHMENT IC D
ONE FOOT
AREA OF FLOOD PLAIN THAT COULD
X:
X:
..................
................. X
DEVELOPMENT BY RAISING::':*:'::'*:*%%.* :X
BE USED FOR ................... -X .....
....... .. ........ ...
GROUND *****-BASE FLOOD ELEVATION BEFORE ENCROACH-:
*%*:::: .. . .......
X
..... ......
ME N ON -.FLOOD. PLAIN . .................
LINE AB IS THE FLOOD ELEVATION BEFORE ENCROACHMENT
LINE CD IS THE FLOOD ELEVATION AFTER ENCROACHMENT
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"Base flood"
The flood having a
one percent chance
of being equaled or
exceeded in
any given year.:` ; It
should be noted that
the magnitude of the
"base flood
is subject to change
as the watershed conditions change: thus,
the term "base flood" as used in
this ordinance may
mean either of two
(2) the design base
floods: (1)
the base flood" bf the
effective FIS or,
flood. See "Design
base flood."
"Desi ,dn base flood" The one - hundred year mean recurrence interval (100 -
year) flood which will result during the design discharge from runoff from
a fully urbanized watershed. For design purposes in this ordinance, it can
be assumed that a 100 -year precipitation event will produce a 100 -year
runoff event.
"Development" Any manmade change to improved or unimproved real estate,
including but not limited to buildings or other structures, mining,
dredging, filling. grading, paving, excavation or drilling operations
located within the floodplain management areas of the City. See
"Floodplain development permit."
"Development permit" See "Floodplain development permit."
"Elevated building" A building located in SFHA Zones Al -99, AE. A, A0, AH,
B, C, X, or D, with the lowest floor elevated above the ground level and
above the design base flood by means of pilings, columns (posts and piers),
or shear walls parallel to the flow of the water and adequately anchored so
as not to impair structural integrity of the building during a flood of up
to the magnitude of the design base flood and further includes a building
elevated by means of fill or solid foundation perimeter walls with openings
sufficient to facilitate the unimpeded movement of flood waters.
"Encroachment" Any activity in a floodplain which hinders the passage of
water or otherwise affects flood flows: e.g. fill, buildings, fences, and
so on.
"Flood elevation determination A determination by the Administrator of
the water surface elevations of the base flood, that is, the flood level
having a one percent or greater chance of occurrence in any given year
under existing or design., conditions.
"Flood elevation study" Ari examination, evaluation and determination of
flood hazards and, if appropriate, corresponding water surface elevations
and/or flood- related erosion hazards under existing or design conditions.
"Flood fringe" or " floodway fringe" The portion of the floodplain
outside of the regulatory floodway but still subject to flooding.
"Flood Hazard Boundary Map" (FHBM) An official map of the flood areas
delineating the boundaries of the flood and related erosion areas having
special hazards designated as Zones A, M. and /or E.
"Flood Insurance Rate Map" (FaM) The official map on which the Federal
Insurance Administration has delineated both the areas of special flood
hazards and the risk premium zones applicable to the City.
"Regulatory fl way" The channel of a river or other watercourse and the
adjacent land areas that must be reserved in order, to discharge the base
flood without cumulatively increasing the water surface elevation more than
a designated height.
"Flood plain," "floodplain land" or "flood -prone area" Any normally dry
land area susceptible to being inundated by water from any source (see
"flooding ") and referenced to some statistical mean recurrence interval.
most frequently the 100 -year mean recurrence interval floodplain.
"Flood plain manakement area" All floodplain lands within the jurisdiction
of the City whether or not the land is within an identified special flood
hazards area.
"Flood plain Development Permit" A permit which must be obtained by any
person before any development begins on land within a floodplain. See
"Development."
SECTION D. Variances
1. Appeal Board The Appeal Board will near and decide appeals and
requests for variances from the requirements of this ordinance. The
City Council will serve as the Appeal Board unless a specific Appeal
Board is otherwise appointed by ordinance.
2. Variance Procedures
a. The Appeal Board shall hear and render judgement on an appeal when
it is alleged there is an error in any requirement. decision or
determination made by the Floodplain Administrator in the
enforcement or administration of this ordinance.
b. Any person aggrieved by the decision of the Appeal Board may appeal
such decision in the courts of competent jurisdiction.
c. The Floodplai4 Administrator shall report any variances, including
the justification for . their issuance, to the Federal Emergency
Management Agency upon request.
3. Variance Conditions
a. Variances shall not be issued within any designated floodway if any
increase in flood levels during the effective FIS base flood
discharge would result.
b. Variances may be issued for new
construction
and substantial
improvements and for other development
necessary for
the conduct
of
a functionally dependent use provided
that all other conditions
of
this section (Section D of Article
4) are met,
and that
the
structure or other development is
protected by
methods
that
minimize flood damages during the
base flood
and create
no
additional threats to public safety.
greater than one -half acre contiguous to, and
surrounded by,
non- complying lots will only be considered with
c. ' Variances may
be issued for the reconstruction, rehabilitation or
restoration of
structures listed on the National Register of
Historic Places
or the State Inventory of Historic Places, without
regard to the
procedures set forth in the remainder of this
ordinance.
d. Variances may
be issued for new construction and substantial
improvements to
be erected on a lot of one -half acre or less in
size contiguous
to, and surrounded by, lots with existing
structures constructed
below the base flood level, for cases of
exceptional hardship,
providing the other relevant factors in Sub-
section 60.6 of
44 CFR 1.1 have been fully considered. Variances
for lot sizes
greater than one -half acre contiguous to, and
surrounded by,
non- complying lots will only be considered with
appropriate technical justification.
e. Upon consideration of the factors noted, and the intent of this
ordinance, the
Appeal Board may attach such conditions to the
granting of variances as it deems necessary to further the purpose
and objectives of
this prdinance.
4. Prerequisites for urant:nq variances
a. Varianct_ shall only be issued upon determination that the
variance is the minimum necessary, considering the flood hazard, to
afford relief.
b. Variances shall only be issued upon:
(1) Showing a good and sufficient cause;
(2) A determination that failure to grant the variance would result
in exceptional hardship to the applicant; and
h
(3) A determination that the granting of a variance will not result
in increased flood heights, additional threats to public
safety, extraordinary public expense, create nuisances, cause
fraud on or victimization of the public, or a conflict with
existing local laws or ordinances.
c. Any applicant .o whom a variance is granted shall be given written
notice that the structure will be permitted to be built with the
lowest floor elevation below the base blood elevation, and that the
cost of flood insurance will be commensurate with the increased
risk resulting from the reduced lowest floor elevation.
6. Foodways
a. Encroachments are prohibited within designated floodways, including
fill, new construction, substantial improvements and other
development unless . ".certification by a registered professional
engineer is provided demonstrating that equal conveyance
encroachments do not result in any increase in flood levels at any
floodplain location and that all other provisions of this ordinance
are met during the occurrence of the base flood discharges.
b. When a floodway has not been designated, no new construction,
substantial improvements, or other development (including fill)
shall be permitted within the 100 -year floodplain until it is
demonstrated that either:
(1) The cumulative effect of the proposed development, will not
increase the water surface elevation of the design base flood
more than oae foot above the August, 1980, FIS, or above the
- most =z , em of f ective Flood Insurance Study base flood
elevations, whichever is less, at any point within the stream:
or,
(2) The cumulative effect of the proposed development, will not
increase the water surface elevation of the design base flood
at any point in the stream above that which would occur without
the proposed development.
DEVELOPMENT PERMI' 'RMIT NO.
PROPERTY WITHIN FLOODPLAIN
STATE OF TEXAS
COUNTY OF DALLAS
CITY OF COPPELL:
NAME OF PERMITTEE:
The above named permittee applied for a DEVELOPMENT PERMIT on
The application has been reviewed by the ADMINISTRATOR and it is his
determination that the proposed development IS located within an
identifiable flood plain of
The ADMINISTRATOR has reviewed plans and specifications of the proposed
development for conformance with the development standards required by
COPPELL flood plain management regulations. You are hereby authorized to
proceed with the following described work:
on the following described property:
To maintain compliance with the development standards of COPPELL flood
plain management regulations and to eliminate or minimize flood damage
potential to the proposed development, you are hereby directed to
construct your proposed development in accordance with the following
special provisions:
( ) For residential structures, the lowest floor (including basement)
must be elevated to two (2) feet above the 100 -year base flood
elevation. Minimum finished floor elevations must be shown on the
plat for the development as approved by the City Engineer. (The
lowest floor must be elevated two (2) feet above BFE, or one (1) foot
above ultimate condition whichever is higher).
( ) For non - residential structures, the lowest floor (including basement)
must be elevated or floodproofed to two (2) feet above the 100 -year
base flood elevation. Minimum finished floor elevations must be
shown on the plat or site plan as approved by the City Engineer.
(The lowest floor must be elevated two (2) feet above BFE, or one (1)
foot above ultimate condition whichever is higher.
( ) Permittee must submit a certification from a registered professional
engineer, architect, or land surveyor that the finished floor level
of the residential structure has been constructed two (2) feet above
the 100 -year base flood elevation, or one (1) foot above ultimate
condition whichever is higher.
( ) For non - residential floodproofing, a registered professional engineer
or architect must certify that the floodproofing methods are adequate
to withstand the flood depths, pressures, velocities, impact and
uplift forces and other factors associated with the base flood.
( ) For fill activities, the permittee must submit a certification from
an engineer or land surveyor that the level of the compacted fill
material is at or above the elevation of the Base Flood.
( ) Provide a certified copy of all final plans or As -Built Drawings to
the ADMINISTRATOR.
( ) OTHER PROVISIONS:
ACKNOWLEDGEMENT OF CONDITIONS BY PERMITTEE DATE
SIGNATURE OF ADM,1111STRATOR
DATE