FLOOD01807

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Title: Guidelines for Determining 100-year Flood Flows For Approximate Floodplains in Colorado
• Date: 1/1/1999
• Prepared For: State of Colorado
• Prepared By: CWCB
• Floodplain - Doc Type: Educational/Technical/Reference Information

1.1.2 Statutory Responsibilities

The CWCB's statutory responsibilities relating to designation and approval of flood water runoff
channels or basins are 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 a4justment of cities, incorporated towns, and counties of this state "..., Section 3 7-60-1 06(1 )(c) of
the Colorado Revised Statues (CRS).

Article 24-65.1-403.3.h of the Colorado Revised Statutes, Title 24, states that .."Nojloodplain shall
be designated by any local government until such designation has been first approved by the
Colorado water conservation board as provided in sections 30-28-111 and 31-23-301.

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 January 30, 1988. The CWCB must comply with these "Rules and
Regulations" ,

Rule 6.B.2, ("Other Requirements" for Hydrologic Analysis for Approximate Floodplain
Information) states that "The hydrology for approximate floodplain information shall, at a
minimum, meet the hydrology standards... for detailed floodplain information". The Guidelines
allow the development of hydrologic information for approximate floodplain maps so they can
comply with Rule 6,B.2,

1.1.3 Limitations of This Publication

The limitations of this publication are as follows:

. lbis publication is intended to be used as a guideline, and the methodology is not mandated by
the State of Colorado, USGS and other hydrologic methods may be used for the purpose of
determining I DO-year flood discharges for streams in Colorado, Drainage criteria and
hydrologic methodologies used by certain local governments and flood control agencies shall
supersede these Guidelines, For example, these Guidelines are not intended to supersede
detailed hydrologic methods established by the Urban Drainage and Flood Control District, the
City of Fort Collins, the City of Colorado Springs, or other local governments.

. The regression equations can be used to estimate peak flow values for the IOO-year flood event
for rural watersheds only.

. The regression equations are for unregulated natural streams only, unless an adjustment can be
made for effective drainage area in those situations where flood control reservoirs, detention

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