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

In addition, an agreement shall be executed between the Board (or the Urban Drainage
and Flood Control District on behalf of the Board if the floodplain below the dams in
their jurisdiction), and the affected local governments that expresses the intent of the
parties to assure that the flood routing capabilities ofthe reservoir will be maintained by
whatever means are available when and if the reservoir owners attempt to make changes
that would reduce the flood routing capability.

Rule 9. Criteria for Determininl! Effects of Levees on Rel!ulatorv Floodnlains:
A. Ownership. Privately owned, operated, or maintained levee systems or flood walls
will not be recognized or considered in the hydraulic analyses that are performed
pursuant to Rule 6 unless a local ordinance rnandates operation and maintenance of the
levee system or flood wall and the minimum standards set forth below are rnet. Levees
and flood walls for which the community, state, of federal government has ownership
and/or the responsibility for operations and maintenance will be considered, provided
that the minimurn standards set forth below are met.

B. Freeboard. A minimum freeboard of3 feet above the Base Flood Elevation shall be
provided along the entire length ofthe levee or flood wall, with the provision of an
additional I-foot offreeboard within 100 feet of either side of hydraulic structures
(e.g., bridges) within the levee or flood wall or wherever the flood flow is constricted.
An additional O.5-foot above the minimum freeboard is also required within 100-feet
of the upstream end and downstream end of the levee.

C. Field Inspection and Maintenance. The levee shall be structurally sound and
adequately maintained. Sedimentation effects shall be considered for all levee
projects. Certification from a federal agency, state agency, or a registered professional
engineer that the levee meets the minimum freeboard criteria as stated above and that it
appears, on visual inspection, to be structurally sound and adequately maintained shall
be required on an annual basis. Levees that have obvious structural defects, or that are
obviously lacking in proper maintenance, shall not be considered in the hydraulic
analysis.

D. Internal Drainage. Where credit will be given to levees providing 100-year
protection, the adequacy of interior drainage systems shall be evaluated. Areas subject
to flooding from inadequate interior drainage behind levees will be mapped using
standard procedures.

E. Human Intervention and Operation. In general, human intervention shall not be
recognized or considered in the evaluation oflevees or flood walls (e.g., capping of
levees by sandbagging, earth fill, or flashboards) for the purpose of increasing the
levee's design level of protection during an imminent flood. Human intervention shall
only be recognized and considered for the operation of closure structures (e.g., gates or
stop logs) in a levee or flood wall system designed to provide at least 100-year flood
protection, including adequate freeboard as set forth above, provided such operation is
specifically included in the community's adopted emergency response plan.

F. Analysis. For areas protected by a levee or flood wall providing less than IOO-year
protection, Base Flood Elevations shall be computed as if the levee or flood wall did

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