BOARD01965

• Board Meeting Date: 3/22/2005
• Description: Flood Section - Presentation of the CWCB's Draft Rules and Regulations for Regulatory Floodplains in Colorado
• Board Meetings - Doc Type: Memo

B. Establishment of Floodway Criteria. The CWCB recognizes that designated floodways are
administrative limits and tools used by communities to regulate existing and future floodplain
developments within their jurisdictions. Communities may choose to delineate floodways
based on FEMA's I-foot rise criteria or based on more strict criteria (e.g., depth and velocity
criteria, 0.5-foot rise, etc.). The CWCB floodway rule is synonymous with communities'
adopted floodway criteria. Where no local floodway criteria exist, the CWCB recommends the
use of the rninimum FEMA standard.

C. Incorporation of FEMA's Floodway Regulations. All regulations defined in 44 CFR
60.3( c)(1 0) and 44CFR 60.3( d) are hereby incorporated by reference into this rule. All
communities participating in the National Flood Insurance Program that have Base Flood
Elevations defined for one or more of the waterways within their jurisdictions are required to
adopt and enforce floodway regulations. Failure to enforce floodway regulations may impact
the community's standing in the National Flood Insurance Program and may eliminate or
reduce eligibility for federal or state financial assistance for flood mitigation and disaster
purposes.

D. Communities in Which This Rule Applies. Communities with designated Regulatory
Floodplains that have Base Flood Elevations defined for one or more ofthe waterways within
their jurisdictions shall be required to establish technical (quantified) criteria for floodway
determination and regulation.

Rule 8. Criteria for Determininl! the Effects of Dams on Rel!ulatorv Floodplains:
A. Flood Control Dams. If a publicly owned, operated and maintained dam is specifically
designed and operated either in whole or in part for flood control purposes then its
effects shall be taken into consideration when delineating the floodplain below such a
dam. The effects of the dam shall be based upon the 100-year flood under foreseeable
development, with full credit to be given to the diminution of peak flood discharges that
would result form normal dam operating procedures.
B. Non-Flood Control Dams. If a dam is not specifically designed and operated, either in
whole or in part, for flood control purposes, then it shall not be recognized as providing
any diminution of peak flood discharges when delineating the floodplain below such
dam. However, if adequate assurances have been obtained to preserve the flood routing
capabilities of such a dam, then the delineation of the floodplain below the dam may,
but need not, be based on the assumption that the reservoir formed by the dam will be
filled to the elevation of the dam's emergency spillway and the I OO-year hydrology can
be routed through the reservoir to account for any flood attenuation effects.
C. Adequate Assurances. For the purposes of Rule 8.B. "adequate assurances" shall, at a
minimum, include appropriate recognition in the community's adopted master plan of:
(I) the flood routing capability of the reservoir, as shown by comparison of the 100-
year floodplain in plan and profile with and without the dam in place in order that the
public may be made aware of the potential change in level of flood protection in the
event that the reservoir flood routing capability be lost, (2) the need to preserve that
flood routing capability by whatever means available in the event that the reservoir
owners attempt to make changes that would decrease the flood routing capability, and
(3) a complete Operations and Maintenance Plan.

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