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Bear Canyon Creek Floodplain Mapping Update

Bear Canyon Creek Floodplain Mapping Update

The City of Boulder has been updating the floodplain mapping for Bear Canyon Creek in south Boulder.

FEMA has accepted the updated floodplain mapping for the section of Bear Canyon Creek downstream of Colorado Ave pdf  and the revised mapping is now in effect.

Project Background

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 and new study technologies.

This Letter of Map Revision (LOMR) was requested in 2014 to update a short reach of the Bear Canyon Creek floodplain. A LOMR is required to formalize flood mitigation improvements and to update hydraulic models.

The City previously submitted a LOMR for Bear Canyon Creek from Foothills Parkway (downstream) to the city limits (upstream) to reflect the numerous changes authorized by City floodplain permits and update hydraulic models based on better, more detailed topographic information. This LOMR was submitted to FEMA in 2002 and approved on February 27, 2003.

The study area for the current LOMR addresses the remainder of Bear Canyon Creek within the City limits, extending from the confluence of Bear Canyon Creek and Boulder Creek (downstream) to Foothills (upstream). This study includes the data and documentation required for accreditation of the Harrison Levee.  The Harrison Levee is provisionally accredited on the current Flood Insurance Rate Maps.  The LOMR will also incorporate the updated hydraulic model for Boulder Creek at the downstream tie-in location and incorporate the additional culverts below Arapahoe Avenue that were installed to increase the conveyance of Bear Canyon Creek.

An open house was held on July 1, with floodplain maps on display for public review.  On July 21, 2014, the Water Resources Advisory Board (WRAB) considered the floodplain mapping update and unanimously recommended that City Council adopt the floodplain mapping update.  On November 18, 2014, City Council approved the floodplain mapping update.  The WRAB and Council memos are available under "Related Links".