ST8805-CS 890126 Federal Emergency Management Agency
Washington, D.C. 20472
The le Lou Duggan Case No.: 89-06-06R
Mayor of e Cit. y of Coppell
P.O. Box 8
Coppell, TeXas 75019
Dear Mayor DUggan:
This is in reference to a letter dated October 10, 1988, and a floodplain
study submitted by Mr. Russell R. Doyle, P.E., City Engineer for the City of
Coppell. In his letter, which was forwarded to us by our Region VI office,
Mr. Doyle requested a conditional Letter of Map Revision (LOMR) for a proposed
fill ~roject along Cottonwood Branch and Denton Creek on behalf of Jerry
Parche Consulting Engineers. The submitted floodplain study entitled Flood-
plain Reclamation Study on Cottonwood Branch and Denton Creek, dated October
1988, prepared by Jerry Parche Consulting Engineers, included the following:
a description of the methodologies used; HEC-2 models of Denton Creek and
Cottonwood Branch representing existing and proposed conditions; and delineations
of the existing and proposed 100-year floodplain boundaries and the proposed
regulatory floodway boundaries on a topographic map. Prior to the commencement
of our review, we received the initial fee of $350.00 for processing a conditional
LOMR request of this type. This fee was sufficient to cover the review and
processing costs associated wi-th this submittal.
As explained in the submitted floodplain study, additional cross sections were
inserted into the HEC-2 models for Denton Creek and Cottonwood Branch (in the
vicinity of Denton Tap Road), which are not reflected in the preliminary Flood
Insurance Study (FIS) for the City of Coppell, dated September 22, 1988.
These models are therefore the best available models and will be used as the
new baseline models in order to evaluate the effects of the proposed project.
It is important to note, ~owever, that these submitted models
swale
We have-~'c~ly'~'~ve~a.~eques.t for a map revision ~rom your communi~
, awaiting the submission of~
specified under Part 65.6
(a) (12) of the N~,al Fl6od
the preliminary Fi~ will not be revised to ref
condi%t°ns until the aforementioned
After reviewing the submitted data, we have determined that the proposed fill
project meets the minimum floodplain management criteria of the NFIP. If the
project is completed as proposed, the 100-year water-surface elevations of
Denton Creek would remain unchanged except at cross section 34850 where an
increase of 0.1 foot would occur. In addition, the 100-year floodplain and
regulatory floodway of Denton Creek would be decreased as indicated in the
submitted floodplain study. Also, if the project is completed as proposed,
the 100-year water-surface elevations of Cottonwood Branch would increase (a
maximum of 0.9 foot) and the 100-year floodplain and regulatory floodway would
be modified as depicted in the submitted floodplain study.
note that the increase in the lO0-¥ear water-surface elevatio~~~--:.
of fill outsidg.9~:the
regulatory
F~ood Insurance
restudie~'~ this. area could modify~this determination.
This determination is based on the 100-year flood discharges computed in the
preliminary FIS for your community, and does not consider subsequent changes
in watershed characteristics that would tend to increase flood discharges.
The development of this project and other projects upstream could result in
increased flood discharges, which, in turn, could result in increased 100-year
flood elevations. Future restudies of your community's flood hazards would
take into account the cumulative effects of development on flood discharges,
and could therefore establish higher 100-year flood elevations in this area.
This conditional LOMR is base,'on minimum floodplain management criteria
established under the NFIP. Your community is responsible for approving all
proposed floodplain developments, including the project upon which this
request is based, and for assuring that necessary permits required by Federal
or State law have been received. State and community officials, based on
knowledge of local conditions and in the interest of safety, may set higher
standards for construction or may limit development in floodplain areas. If
the State of Texas or the City of Coppell has adopted more restrictive or'
comprehensive floodplain management criteria, these criteria take precedence
over the minimum NFIP requirements.
Please note the requirements for floodway revisions as outlined in NFIP
regulation Part 65.7 (b)(1) (copy enclosed), which states that when a floodway
change is proposed, a copy of a public notice distributed by the community
stating the community's intent to revise the floodway, or a statement by the
community that it has notified all affected property owners and affected
adjacent jurisdictions must be submitted to the Federal Emergency Management
Agency (FEMA). This requirement must be addressed when requesting a map
revision to reflect the effects of the completed fill project.
We have enclosed a copy of Part 65 of the NFIP regulations, which further
describes the nature and extent of the material needed to support a request to
revise an effective FIS, FIRM, and FBFM. Compliance with the criteria outlined
in this document will expedite F~A's review process, thus allowing the
effective FIS, FIRM, and FBFM for your community to be revised as appropriate,
in a timely manner.
Should you have any questions regarding this matter, please do not hesitate to
contact the Chief, Natural and Technological Hazards Division of the Federal
Emergency Management Agency in Denton, Texas, at (817) 898-9127 or Matthew B.
Miller of our Headquarters staff in Washington, D.C., at (202) 646-3461.
Sincerely,
Chief, Risk Studies Division
Federal Insurance Administration
Enclosure
cc: Mr. Russell R. 9oyle, P.E.
Mr. Jerry Parche, P.E., Jerry Parche Consulting Engineers