FLOOD03761

• County: Statewide
• Basin: Statewide
• Title: Guidelines for Determining 100-Year Flood Flows for Approximate Floodplains
• Date: 5/12/1995
• Prepared By: CWCB
• Floodplain - Doc Type: Project

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STATE OF COLORADO

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Colorado Water Conservation Board
Department of Natural Resources

721 State Centennial Building
1313 Shennan Street
Denver. Colorado 80203
Phone [phone]
FAX [phone]

Roy Romer
Governor

MEMORANDUM

James S. Lochhead
Executive Director. DNR
Danes eWe, P.E.
Director, eWeB

TO: Colorado Water Conservation Board Members

FROM: Larry Lang

DATE: March 3, 1995

SUBJECT: Agenda Item lOb, March 13-14, 1995, Board Meeting--
Designation Standards for "Approximate" Floodplains

INTRODUCTION

The CWCB has certain statutory responsibilities relating to designation and
approval of flood water runoff channels or basins as follows:

... "to devise and formulate methods, means, and plans for bringing about the
greater utilization of the waters of the state and the prevention of flood damages
therefrom, and to designate and approve storm or floodwater runoff channels or
basins, and to make such designations available to legislative bodies of cities and
incorporated towns, to county planning commissions, and to boards of adjustment
of cities, incorporated towns, and counties of this state "..., Section 3 7-60-106(1)( c)
of the Colorado Revised Statues (CRS).

The CWCB designates and approves the state's floodplains under the provisions of its "Rules and
Regulations for the Designation and Approval of Floodplains and of Storm or Flood Runoff
Channels in Colorado", dated 1/30/88. The CWCB must comply with these "Rules and
Regulations". Colorado statutes require that local governments obtain from the CWCB the
designation and approval of floodplain information prior to its use for regulatory purposes,
whether those delineations are approximate or detailed.

The "Rules and Regulations" include specific technical standards for approximate floodplain
information. Certain provisions are more lenient than the standards for detailed floodplain
information with regard to base topographic information and hydraulic analyses. However. the
technical standards for approximate and detailed floodplain information are essentiallv equivalent
with regard tohvdrologic analvses. If approximate floodplain mapping is based on a hydrologic