Floodplain Management

Boulder County Flood 2013 information and resources
Boulder County joined the National Flood Insurance Program in 1974 and the county has been active in floodplain management since that time. The goals of the program are to:
  • reduce flood hazards,
  • regulate floodplain activities,
  • adopt floodplain policies,
  • map floodplains, and
  • educate the public about floods and floodplains.

View the Boulder County 2013 Floodplain Management Activities Summary and Update* (annual report)

*NOTE: The 2013 annual progress report of the county’s floodplain management program is a required activity of its participation in the National Flood Insurance Program’s Community Rating System (CRS). Each year, communities are required to recertify their activities in CRS over a twelve month period. Boulder County’s recertification is due October 1st each calendar year.

Due to the September 2013 Flood, Boulder County was given a six month extension to complete its CRS recertification. Although the progress report was delivered in April 2014, the reporting period is 10/1/2012 – 10/1/2013 and does not include many detailed activities relative to the September 2013 Flood. The 2014 annual progress report (due by October 2014) will cover post-flood response and activities in more detail.


Interim Floodplain Map

The county is in the process of acquiring updated floodplain information as a result of the changes cause by the September 2013 flood. Please see the Interim Floodplain Map information page for updates on the information that is currently available.


Floodplain Maps

Boulder County has 13 major drainages with mapped floodplains. The floodplain maps provide the foundation for Boulder County's floodplain management program. Floodplain maps direct the program goals by identifying areas at risk during times of flood that threaten life and safety.

The floodplain maps help property owners determine if their property is at risk for flooding and if the property is within a regulatory floodplain.

List of Floodplain Maps

These maps are for illustration purposes only. For an official determination about your property contact the Transportation Department at floodplainadmin@bouldercounty.org or 303-441-3900

 Flood Preparation

Flood Preparation

Boulder County is vulnerable to stream and creek flooding and flash floods. Flooding along streams is a natural and inevitable element of nature.  Some floods occur seasonally when spring rains and melting snows fill drainage basins.

Most flash floods are caused by slow-moving thunderstorms or thunderstorms repeatedly moving over the same area.  Flash floods are not confined to major drainage ways.  Changes to the landscape can increase the risk of flash floods.

The area of the Fourmile Fire experienced increased runoff and areas not known for flooding experienced severe flash floods, flood damages, and debris deposition associated with summer thunderstorms.

Floods can happen with as little as 45 minutes of warning. By understanding the dangers of floods and flooding, property owners at risk can be prepared and save lives.


Regulatory Requirements

Through enforcement of current regulations, preservation of floodplains, and development of hazard mitigation and emergency response plans, Boulder County has been able to preserve flood prone areas, prevent adverse impacts and unwise uses in the floodplain.

Collaborative work by Boulder County with outside agencies through stream enhancement, mitigation and flood control projects has demonstrated a focus on accommodating floods instead of controlling them.

If you are a property owner and want to build on your property, you may need to meet certain requirements.

Development Requirements



Interim Floodplain Map

Interim floodplain maps based on information obtained after the September 2013 flood are now available. There are currently no floodplain development permit requirements for properties that are on the interim floodplain. However, Boulder County recommends considering the interim floodplain map when making development decisions.

 Drainage & Flood Control

Drainage and Flood Control

The Transportation Department coordinates with outside agencies, other government jurisdictions and the public on:

  • storm water drainage
  • flood control
  • hydrology and hydraulic engineering

Storm Water Drainage

Boulder County is a member of the Keep It Clean Partnership which is dedicated to protecting water quality and reducing stormwater pollution.

The Keep It Clean Partnership has developed programs to meet requirements established by the EPA regarding stormwater regulations. These regulations require our communities to help maintain water quality and stream health. Maintaining clean water is critical to both our health and the health of our ecosystem.

Flood Control

Boulder County is located within the Urban Drainage and Flood Control District. Urban Drainage was created to assist local governments with drainage and flood control problems.

As part of the Urban Drainage, Boulder County receives help in floodplain management to prevent new sources of flooding, flood warning forecasts and design, construction and maintenance for specific development projects within the floodplain.

Hydrology and Hydraulic Engineering

Boulder County supports and participates in periodic updates to the floodplain maps with neighboring communities and FEMA. These updates ensure that the floodplain maps reflect current conditions.

Flood Control Information

South Boulder Creek Proposed Floodplain

Resolution 2007-93, an emergency resolution imposing a temporary moratorium of reasonable duration on Boulder County's processing of applications for proposed land development in the unincorporated area which is shown on the revised 100-year floodplain in the City of Boulder's South Creek flood mapping study as submitted to the Federal Emergency Management Agency on August 17, 2007.

  • Adoption of Resolution 2007-93 and Extension of Floodplain Moratorium Resolution 2007-124
  • Public Hearing Notice for November 13, 2007 Regarding South Boulder Creek Floodplain Moratorium
  • Resolution 2007-93 Revised Floodplain Document
  • Revised 100-Year Floodplain Map


Request More Information

Floodplain Information is available for areas within unincorporated Boulder County. If your property is located in another municipality, please contact that city or town.

Useful Links

Contact Us

Contact Boulder County Floodplain Administrator, floodplainadmin@bouldercounty.org, 303-441-3900.