Skunk Creek, Bluebell Canyon Creek, and King's Gulch Floodplain Mapping Update
The City of Boulder has updated the floodplain mapping for Skunk Creek, Bluebell Canyon Creek, and King’s Gulch. The updated mapping was approved by City Council on April 4, 2017 and is regulatory. FEMA approved the mapping with an effective date of May 31, 2018. To view the revised floodplain mapping and more information about the study, see the links on the right side of this page.
Floodplain mapping studies provide the basis for flood management by identifying the areas subject to flooding. This information is essential for determining areas where human safety is threatened and property damage is likely. Floodplain maps must be updated periodically to reflect changes in the floodplain resulting from land development, flood mitigation improvements, new study technologies and the impacts of major floods that may have occurred.
Skunk Creek, Bluebell Canyon Creek, and Kings Gulch were first studied by Greenhorne & O'Mara in 1987. The resulting Flood Hazard Area Delineation (FHAD) delineated the 100-year floodplain along these creeks. The Flood Insurance Study (FIS) and Flood Insurance Rate Map (FIRM) approved for these creeks were originally based on the 1987 FHAD and included a federally-regulated one foot rise floodway. In 1989, Love and Associates delineated the High Hazard Zone and City of Boulder Conveyance Zone (1/2 foot rise floodway). The delineations were based on the hydraulic models used in the 1987 FHAD.
On May 6, 1991, FEMA issued a Letter of Map Revision (LOMR) for Skunk Creek. The limit of the LOMR was in the University of Colorado’s Research Park, downstream of Colorado Avenue to just upstream of the confluence of Boulder Creek.
The Skunk Creek floodplain mapping update project began in 2007 to incorporate the pedestrian underpass and culvert for Skunk Creek at 27th Way into the effective flood insurance rate map (FIRM). Since then, the project was expanded to include the entire regulatory lengths of Skunk Creek and the Skunk Creek tributaries of Bluebell Canyon Creek and Kings Gulch. In late 2013, the original engineering consulting firm working on the mapping update project closed their offices. The City then contracted with ICON Engineering to complete minor changes to the completed floodplain mapping to reflect changes as a result of the observations from the September 2013 flooding event. Following these changes, the proposed mapping update was presented to the Water Resources Advisory Board (WRAB) who recommended that the project undergo an additional peer review of the proposed mapping update.
In January 2015 the additional peer review was completed and among other things, recommended that the spill flows north across Baseline Road from Bluebell Canyon Creek, and spill flows north east across US Highway 36 from Skunk Creek be explored further and documented with the floodplain mapping update. Additional review and analysis resulted in questions about the hydrology of the watershed, so a new hydrologic evaluation was initiated in 2015.
The revised mapping was submitted to FEMA for their review and subsequent adoption (FEMA Case #17-08-0797P ). The mapping has been approved by FEMA and becomes effective on May 31, 2018.
Please see the FAQs on the right side of the screen under "Skunk Creek Resources" for more information about the floodplain mapping process.