FLOOD08491

• Designation Number: 402
• County: Rio Blanco
• Community: Rangely
• Stream Name: White River
• Basin: Yampa/White
• Title: Floodplain Information Report - White River From Rio Blanco Lake to Utah-Colorado State line
• Date: 4/1/1996
• Designation Date: 5/1/1996
• Floodplain - Doc Type: Floodplain Report/Masterplan

5.0 INTERPRETATION OF TillS REPORT

5.1 Hvdi-ologic Findings

The results of the hydrologic analysis for the White River are considered accurate. They are
based in part on existitJ.g approved data.

5.2 Hvdraulic Findin~s

The hydraulic methods used for this study are similar to those used in more detailed studies and
much more detailed than the typical approximate studies. The 100-year flood depths range from
7.4 feet in a medium width reach of the river to 13.1 feet at the downstream limit of the study.
The flood depths are generally consistent throughout the study reach with differences of a few
feet (8-13 feet for 100-year flow depths).

5.3

FloodDlain Delineations

The primary difficulty in presenting precise delineation of the 50-year and 100-year floodplains
was the limited quality of the available base mapping for the lower White River. Using USGS
topographic quadrangle maps at contour intervals of 20 or 40 feet to portray flood lines in
unsurveyed areas provides limited information. The margin for interpretation is very great,
especially in wider reaches of the river where contours are widely spaced. More detailed
topographic information will be needed in areas of specific interest.

This study can be utilized to prepare more detailed floodplain delineations in such areas of
specific interest. Those who are interested in greater detail have three choices for using this
study:

1) They can refer to the detailed study information for the stream reach in and around
Rangely;
2) They can rely on the hydrologic determinations and use other topographic information and
hydraulic models; or
3) They can use the depth calculations with other topographic information from field surveys
or other maps.

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6.0 REFERENCES

1. Federal Emerllencv Manallement Allencv; Flood Insurance Study and Flood Insurance
Rate Map dated September, 1990; Town of Rangely, Colorado.

2.

Federal Emerllencv Manallement Allencv; Flood Insurance Study and Flood Insurance
Rate Map dated September, 1991; Town of Meeker, Colorado.

3.

Federal Emerllencv Manaflement Allency; Flood Insurance Study and Flood Insurance
Rate Map dated February, 1990; unincorporated Rio Blanco County, Colorado.

4.

Merrick and Comvanv: Floodplain Information Report on the White River, Sulphur Creek,
and anderson Heights Drainageway, Town of Meeker, Colorado.

5.

United States Geolollical Survey: Water-Data Report, Water Resources Data, Colorado,
Water Year 1993.

6.

Curve fit Prow-am: A public domain computer program, version 1.0 by T. S. Cox

7.

Chow. Yen Te; Open Channel Hydraulics, 1959

8.

OANY; An in-house hydraulics computer program (not for public domain)

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