FLOOD01280

• Designation Number: 93
• County: Jefferson
• Community: Lakewood
• Stream Name: McIntyre Gulch
• Title: Flood Hazard Area Delineation - McIntyre Gulch, Lakewood, CO
• Date: 10/1/1977
• Designation Date: 1/1/1978
• Floodplain - Doc Type: Floodplain Report/Masterplan

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water surface elevation was obtained from the results of the rating of
the bridges, culverts, and detention routing. Discharge and corresponding
water surface elevations for the future development condition 10 and 100
year flood were input and backwater profiles calculated. These data were
then plotted on the 1" = 100', 2 foot contour interval mapping and the 100
year flood plain was outlined (see sheets 3 to 14 in the Appendix).
D. Flood Plain and Floodway Data
A feature of the floodplain regulations of the U.D. & F.C.D. and City
of Lakewood is the provision for the subdivision of the Flood Regulatory
District (flood plain) into the Floodway District and the Flood Storage
District. The difference in the flood districts is the degree of regulation;
the Floodway District has strict regulations, whereas the Flood Storage District
is developable under certain conditions. The flood plain and floodway
information have been determined for this study.
To define the floodway, the flooded overbank area of.the channel was
reviewed for the 100 year flood water surface. If the depth was less than or
equal to 2 feet and the flow velocity was less than or equal to 4 fps, then
the overbank area was subdivided into the Flood Storage District. However,
the division must not cause a 100 year flood water surface profile rise of
more than one-half (0.5) foot above that for the Flood Regulatory District
based on the assumption that there will be an equal degree of encroachment
extending for a significant reach on both sides of the stream.
The flood plain and floodNay data have been tabularized (Table 5) for
the cross-sections used in the backNater analysis. The sections are referenced
to the channel station (sta 0+0 taken at the confluence of McIntyre Gulch
with Lakewood Gulch), and the locations are shown on sheets 3 to 14 in the

Appendix. The tabularized data for the flood plain include the 100 year
flood discharge, the thalweg elevation (the lowest point in the stream
bed), the 100 year flood elevation, and the 100 year flood plain width.
The tabularized data for the floodway include the distance left and right
of the thalweg, the total floodway width, and the floodway elevation.

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