Gregory Canyon Creek Letter of Map Revision (LOMR) - Home

We appreciate your interest in the Gregory Canyon Creek Letter of Map Revision (LOMR) Project. This Web site contains information about the floodplain model, the project team and the opportunities for public involvement.

• Public Involvement/Meetings
• Flood insurance information
• Project Team
• Contact Us

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Introduction:

The City of Boulder has developed a floodplain model for Gregory Canyon Creek (GCC) that will potentially update and replace both the Federal Emergency Management Agency's (FEMA) Flood Insurance Rate Map (FIRM) and the City of Boulder floodplain map. This new model will simplify the floodplain management of GCC by providing one regulatory floodplain map for both the city and federal governments. The proposed mapping revision also incorporates more accurate topographic information and improvements along GCC that have occurred since the effective floodplain map was approved by FEMA in 1987.

New floodplain maps are being developed based on:

• Updated and more accurate topographic data;
• Identification of previously unmapped flow paths; and
• Updated floodplain, floodway and high hazard zone boundaries.

Based on this new information, some structures will be removed from the high hazard zone, while others will now be included.

Background:

Floodplain mapping studies provide the basis for flood management by identifying the areas subject to flooding. This information is essential in determining areas where life safety is threatened and damage to property is likely. Floodplain maps need to 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.

The Gregory Canyon Creek Flood Mapping Study (GCC FMS) will update the Gregory Canyon Creek Floodplain map. The existing FEMA FIRM is based on an approximate floodplain delineation that only shows floodplain boundaries. The existing City of Boulder floodplain map is a detailed, though dated, delineation of the floodplain that includes floodplain boundaries, water surface elevations, conveyance zones and high hazard zones. The new study will establish floodplain boundaries, water surface elevations, conveyance zones and high hazard zones using current methodology and will include improvements and changes along GCC that have occurred since the current maps were approved by FEMA in 1987.

Floodplain Study Overview:

The GCC FMS evaluates the floodplain from the area upstream of Flagstaff Road to the confluence with Boulder Creek, which is approximately 1.2 miles of stream. The floodplain mapping study and floodplain work maps of the project area are included below:

•  Gregory Canyon Creek Letter of Map Revision Study
•  Gregory Canyon Creek Work Maps

Study Results - Impacts to Structures:

Based on updated and more accurate topographical data, land use changes since 1987 and identification of previously unmapped flow paths, floodplain, floodway and high hazard zone boundaries have been updated and changed from the existing floodplain maps. Based on these changes, some structures have been removed from the floodplain, floodway and high hazard zones while others have been identified that now place them in these areas. The graphics below indicated the changes in floodplain designation that have occurred for all structures in the old and new floodplain. These exhibits depict the changes as they relate to changes in floodplain, floodway and high hazard zones.

Please note that the graphics and associated address tables may not be completely comprehensive due to data limitations. Enhancements and modification to the list will continue to be made as the floodplain adoption process moves forward.

•  Public information for structure floodplain status address mapping and tables
  
  
•  100-YEAR Effective FEMA vs. Proposed Floodplain Property Data

•  100-Year Effective City vs. Proposed Floodplain Property Data
  
  

•  FLOODWAY-PROPERTY DATA
  
  

•  HIGH HAZARD-PROPERTY DATA

Confluence with Boulder Creek to Pleasant Street

•  100-YEAR Effective FEMA vs. Proposed Floodplain-Confluence with Boulder Creek to Pleasant Street

•  100-Year Effective City vs. Proposed Floodplain - Confluence with Boulder Creek to Pleasant Street
  
  
•  500-YEAR FLOODPLAIN-Confluence with Boulder Creek to Pleasant Street

•  FLOODWAY-Confluence with Boulder Creek to Pleasant Street
  
  

•  HIGH HAZARD-Confluence with Boulder Creek to Pleasant Street

Arapahoe to Euclid Avenue

•  100-YEAR Effective FEMA vs. Proposed Floodplaion-Arapahoe Avenue to Euclid Avenue
  
  
•  100-Year Effective City vs. Proposed Floodplain - Arapahoe Avenue to Euclid Avenue
  
  
•  500-YEAR FLOODPLAIN-Arapahoe Avenue to Euclid Avenue
  
  
•  FLOODWAY-Arapahoe Avenue to Euclid Avenue
  
  
•  HIGH HAZARD-Arapahoe Avenue to Euclid Avenue

Euclid Avenue to Flaggstaff Road

•  100-YEAR Effective FEMA vs. Proposed Floodplain-Euclid Avenue to Flagstaff Road
  
  
•  100-Year Effective City vs. Proposed Floodplain - Euclid Avenue to Flagstaff Road

•  500-YEAR FLOODPLAIN-Euclid Avenue to Flagstaff Road
  
  
•  FLOODWAY-Euclid Avenue to Flagstaff Road

•  HIGH HAZARD-Euclid Avenue to Flagstaff Road

Last Updated on Wednesday, 08 July 2009 07:48