FLOOD08632

• County: Clear Creek
• Community: Silver Plume
• Stream Name: Clear Creek
• Basin: South Platte
• Title: Clear Creek Project - Clear Creek at Silver Plume, Engineering Correspondence
• Date: 10/9/1997
• Prepared For: Clear Creek
• Prepared By: Consultants
• Floodplain - Doc Type: Community File

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Colorado Water Conservation Board
Department of Natural Resources
721 Centennial Building
1313 Sherman Street
Denver, Colorado 80203
Phone: [phone]
fAX, (3031866-4474

STATE OF COLORADO

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October 9, 1997

Roy Romer
Covernor

Me. John Liou
FEMA Region 8
Denver Federal Center, Building 710
Denver, Colorado80225-0267

James S.lochhead
Executive Director, ON R

Daries C. lile, PE.
Director, ewes

RE: Hydrology for Clear Creek at Silver Plume, Colorado

Dear John:

The Colorado Water Conservation Board (CWCB) has prepared revised flood-frequency
relationships for Clear Creek at Silver Plume, Colorado. The CWCB's hydrologic analysis
made use of the regional regression equations as published in the U.S. Geological Survey's
(USGS) Water Resource Investigations Report entitled "Analysis of the Magnitude and
Frequency of Floods in Colorado." This publication, which is currently in draft form, was
developed by J.E. Vaill of the USGS in cooperation with the Colorado Department of
Transportation and the Bureau of Land Management. As you recall, I previously forwarded a
copy of the draft USGS report to you for review. The information contained in the USGS report
should provide you with sufficient technical backup information regarding the hydrologic
methodology and the development of the regional regression equations.

The CWCB's proposed peak flow values are presented in table 1. For comparison purposes, the
Corps' proposed values and the original FIS values are also listed in table L

Please review the transmitted information and let me know if you are satisfied with the
hydrologic methodology that was used for Clear Creek at Silver Plume. If the methodology is
acceptable, then I will proceed with the analysis for the remaining portions of Clear Creek and its
tributaries upstream of Lawson. Upon completion of the analyses for all streams and locations, I
will submit a complete hydrology report that includes technical backup data and correspondence
for this project. If you have any questions or need additional information, please give me a call.
Thank you for your patience.

Thomas W. Browning, P.E.
Project Engineer, Flood Control and Floodplain Management Section

c:\seca\projects\clr-crk\liou- 2.doc