FLOOD10387 ‎(2)‎

• County: Statewide
• Stream Name: Yampa River
• Title: Floodplain Information Report - Volume 1 - Yampa River from Craig to Dinosaur National Monument
• Date: 5/1/1995
• Prepared For: Recovery Implementation Program for Endangered Fish Species in the Upper Colo
• Prepared By: CWCB
• Floodplain - Doc Type: Floodplain Report/Masterplan

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TABLE 5
YAMPA RIVER CROSS-SECTION IDENTIFICATION

..-,.....-......... -........,.. .............
................................................
.................................................
................................................
.................,................,..............
. .............. ..., ..............,.............
FwWVALtJES lCFSf
~~~ti#)@+~}.....}m
..~.

15800, 18300 (Yl) NONE
15800, 18300 (Yl) A-A'
16651, 18791 (Y2) B-B'
17102, 19052 (Y3) C-C'
17102, 19052 (Y3) D-D'.
17102, 19052 (Y3) NONE
18315, 19776 (Y4) F-F'
18315, 19776 (Y4) G.o'
18548,20003 (Y5) H-H'
18548,20003 (Y5) I-I'
18548,20003 (Y5) I-I'
18548,20003 (Y5) NONE
19748, 21433 (Y6) K-K'
35842, 40481 (Y7) L-L'
36497, 41322 (Y8) M-M'

DETAILED STUDY
ALREADY PERFORMED

FEMA STUDY

3

CALCULATED

2 (FROM F-F')
2 (FROM F-F')

CALCULATED

CALCULATED

CALCULATED

CANYON REACH

N/A

CALCULATED

CALCULATED

3
2 (FROM F-F')
2 (FROM G.o')
CANYON REACH

CALCULATED
CALCULATED
CALCULATED

N/A

CALCULATED

2 (FROM D-D')
2 (FROM G.o')

CALCULATED

CALCULATED

Map-derived cross-section E-E' was prepared, but it was not used. It was omitted because the
field- surveyed cross-section, 0-0', located in the same reach, better represents that reach.

4.4 Computing Flood Depths

Flood depths were calculated at each cross-section through a computer program (QANY) which
uses Manning's equation. The input parameters for the calculation of flow included: x and y
coordinates for points on the cross-section, Manning's 'n' values (ranging from 0.03 to 0.035 for
the channel and 0.045 to 0.05 for the overbank) (Reference 7), the channel slope (interpreted
from USGS quadrangle maps), and depth values. The program calculated flow and velocity
values for each depth value entered. The target flow values were those values established in
Section 3.0 and shown on Table 3. Rating curves were established from the calculated depths.
From the rating curves 50-year and 1 DO-year flood elevations were established at each location.

In performing the depth calculations the flow on the river the day of the survey was obtained
from the USGS and subtracted from the established 50-year and 1 DO-year flows for each
particular hydrologic point. The depth of water on the day of the survey was estimated and
added to the flood depth calculations to obtain the true flood depths shown in Table 6. The

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