Floodplain Study ltr.Kimley. Horn and Associates, Inc. 12660Coit Road, Suite200, Dallas, Texas 75251 · (214) 386-7007 ~
Raleigh, Durham, Charlotte, Nashville, Virginia Beach Washington, Dallas,
December 23, 1087 West Palm Beach, Tampa, Or~ande, Ft. Lauderdale, VeroBeach, FtMyers, Phoenix
Mr. Kevin Peiffer
Ginn, Inc.
17103 Preston Road - Suite 100
Lock Box 118
Dallas, Texas 75248
re: Creek View Addition - Floodplain Study
Grapevine Creek - Coppell, Texas
Dear Mr. Peiffer:
We have completed a review of the submittals by Nathan D. Maier Consulting
Engineers, Inc. (NDM) on the above project. Submittals reviewed include
data from HEC-2 computer models of 12/18 and 12/21/87 as well as their
earlier models. As you requested, these reviews have been made in light of
their petition of 12/18/87 for a variance to the new City of Coppell
Floodplain Management Ordinance.
To summarize our reviews, the project as proposed will have little effect
on the Grapevine Creek floodplain. That is, the impacts on the effective
flood insurance study (FIS) base flood are nil; the impacts on the ultimate
conditions 2-yr flood event are nil; and, although they are evident, the
impacts on the ultimate conditions base flood (the design base flood) are
felt to be minimal and within acceptable limits.
Design base-flood velocities increase at four locations, in areas already
having erosive velocities, but in reaches having large floodplain limits to
accommodate erosion and meandering which may result from those future
velocity increases. Other design base-flood velocity increases are less
than 0.1 fps in locations of non-erosive velocities, assuming 8 fps is the
erosion threshold velocity. Further, the design base-flood water surface
elevations increase from less than 0.1 ft to less than 0.3 ft at seven
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