FLOOD06551

• County: Moffat
• Community: Craig
• Stream Name: Yampa River
• Basin: Yampa/White
• Title: Floodplain Information Report
• Date: 4/1/1996
• Prepared For: Routt County
• Prepared By: CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Based on these standards, there were 15 separate stream reaches classified for a total of 57 river
miles. That is an average of 3.8 miles per reach. These 15 stream reaches are listed in Table
4 :L.-:d they are shmvn on Figure 6.

4.0 HYDRAULIC ANALYSIS

4.1 Base Manning

Base mapping selected for the delineation of the 50-year and 100-year floodplains on the Yampa
River consisted of7.5 minute U.S.G.S. topographic quadrangle maps. A total of 14 quadrangle
maps were used in compiling the base maps for the Yampa River study reach. The contour
interval for the maps was either 20 or 40 feet (see Figure B). Due to the small scale of the base
maps (1 "=2000'), the 50-year and 100-year floodplain boundaries could not be shown as separate
in most cases.

4.2 Stream Reaches

Preliminary work on the floodplain mapping of the Yampa River included dividing the entire
study into separate reaches. The reaches were classified by estimating stream floodplain widths.
The width classifications were refIned once cross-sections were plotted. The width classifications
selected are based on the distance from one side of the river to the other at a ground elevation
15 feet above the low water level. Those classifications are:

Broad
Medium
Narrow
Canyon

>0.5 mile wide;
0.2 - 0.5 mile wide;
0.1 - 0.2 mile wide;
<0.1 mile wide.

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