FLOOD05356

• County: Jefferson
• Community: Jefferson County
• Stream Name: Cub Creek
• Basin: South Platte
• Title: Request for Conditional Letter of Map Revision for Cub Creek
• Date: 6/1/1992
• Prepared For: State of Colorado
• Prepared By: Greenhorne & O'Mara, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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VII.

The hydraulic anlllysis terminates at Station 3344 (HEC-2 Section 118) which

is approximately at FIS Section V. A comparison of water surface elevations

at FIS Section V are summarized below:

Flood Event
IO-Year
50-Year
lOO-Year
500-Year

FrS Section V
7124.6
7127.6
7128.5
7130.5

CLOHR Section 118
7123.6
7128.3
7129.2
7131. 2

Proposed elevations match the existing FIS elevatiDns at Section W within 1.0

feet for all storm frequencies. New flood profiles were plotted for the

proposed improvements. The upstream water surface elevations are extended past

Section V and are shown tied into FIS Section X (Figure F).

Enclosed in the A;ppendix are copies of the HEC-2 files

runs (IO-year, 50-year, 100-year, and 500-year

improvements and for the updated existing condition.

for the multiple profile
events) for proposed

It should be noted that a floodway was not computed for the original Jefferson

County Flood Insurance Study. Therefore, no floodway data was completed for

this CLOHR submittal.

SUlIItARY

Existing floodpla.in conditions were redefined for this study based on more

detailed and up to date mapping. 100-year flood elevations generally range

from 0 to 3 feet higher than the FIS through the study reach. This difference

can be attributed to the new detailed mapping which shows significant

differences in channel invert elevations from the original study.

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