Colorado Floodplain Rules

In an effort to increase public safety and reduce flood losses across the state, the Colorado Water Conservation Board issued new floodplain rules and regulations that became effective on January 14, 2011.  These rules build off of the FEMA rules with the hope to provides uniform standards for regulatory floodplains in Colorado and activities in those floodplains.  For your reading pleasure, the rules can be found here: http://cwcb.state.co.us/legal/Documents/Rules/CWCBFloodRulesRegs2010.pdf.

One of the more stringent criteria found in the CWCB rules concerns floodway designation.  The floodway is defined as the channel of a river or other watercourse and the adjacent land areas that must be kept free of obstructions in order to discharge the base flood without cumulatively increasing the water surface elevation more than a designated height.  In the past this designated height was one foot. However, with the new Colorado rules this has been reduced to ½ foot.  The following is an exerpt from the CWCB rules concerning floodway designation:

The CWCB recognizes that Designated Floodways are administrative limits and tools used by communities to regulate existing and future Floodplain developments within their jurisdictions. This Rule 8(A) does not require communities to automatically map ½ foot floodways within their jurisdictions. However, at such time when floodways are to be delineated through Physical Map Revisions involving local government participation, communities shall delineate floodways for the revised reaches based on ½-foot rise criteria. Letters of Map Revision to existing floodway delineations may continue to use the floodway criteria in place at the time of the existing floodway delineation. Until such time that floodways are revised and designated, communities may continue to regulate their mapped one-foot floodways. For reaches where a transition must be shown to connect new studies to existing studies with different floodway criteria, the transition length shall not exceed 2,000 feet.

Special interests within the state have expressed their opposition to the floodway change.  Sand and gravel pits are often located adjacent to rivers.  By reducing the floodway height to a ½ foot the limits of the floodway will expand thereby pushing the sand and gravel operations further from the river.

For municipalities across the state a three year transition period beginning from the effective date of these rules will be in effect during which all local governments may follow current local ordinances but must undertake activities to come into compliance with these Rules. Following this transition period, all floodplain activities shall be in conformance with the new rules.

Baseline Engineering Firm is poised to support both private interests and governmental agencies through this process.  Our water resource engineers are experts in the fields of hydrologic and hydraulic modeling.

For more information, please contact Chris Rundall by email (chris (at) baselinecorp.com) or phone at (303) 940-9966.

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