Surface Water Management Division

Flood Hazard Management Planning 

The county addresses flood control issues through a comprehensive flood hazard management planning program that incorporates a selection of planning, engineering, and environmental protection measures. Traditional flood control measures generally refer to engineering projects intended to control flood waters, such as the building of levees and dikes and dredging rivers. Nationwide the current focus is on floodplain management, which refers to the operation of an overall program of preventative measures to reduce flood damage.

Oso Levee

The county’s floodplain management actions include:

• Participation in the National Flood Insurance Program,
• Adoption of floodplain development regulations (see PDS Bulletin #42) that meet NFIP requirements,
• Participation in an NFIP incentive program, Community Rating System (CRS),
• Emergency preparedness plans, and
• Comprehensive flood hazard management plans for the main rivers, which propose actions to minimize future flood damage. The completed plans can be accessed from this Web page, and are listed below.

Also listed below is some general information on flood hazard management issues in the county, and the Snohomish County Flood Insurance Study (FIS). This study developed the flood risk data for the various areas of the county, which is used to establish flood insurance rates and as a basis for the county’s floodplain management programs. The analyses used to prepare the FIS are also used to prepare the Flood Insurance Rate Maps (FIRMs), which show flood hazard areas in the county. The FIS provides information to supplement the FIRM.

• Flood Hazard Management Issues in Snohomish County (view pdf document)
• Snohomish County Flood Insurance Study (large document broken into smaller pdfs)

Volume 1 of 2	Volume 2 of 2
Part 1 Part 2 Part 3 Part 4 Part 5 Part 6	Part 1 Part 2 Part 3 Part 4 Part 5 Part 6 Part 7 Part 8 Part 9 Part 10

• See FEMA tutorial, How to Read a Flood Insurance Study

 Floodplain Mapping

The county partnered with FEMA to update and digitize the flood insurance rate maps for Snohomish County. The newly updated and digitized FIRMs were released on September 28, 2010, and the adoption process is pending. To find out more, please view the DFIRM project Web pages.

To fulfill its mandate to identify floodprone areas, FEMA has an ongoing program to produce updated FIRMs for communities with maps. Upon completion of a floodplain mapping project, the mapping partner submits final draft materials, in the Technical Support Data Notebook (TSDN) format to FEMA for review and processing.

Technical Support Data Notebooks

Available TSDNs for flood mapping projects completed in Snohomish County are listed below:

• Lower Skykomish River and Snoqualmie River Floodplain Mapping Project TSDN (pdf)
• Upper Skykomish River Floodplain Mapping Project TSDN (pdf)
• Snohomish River Floodplain Mapping Project TSDN
  • Technical Support Data Notebook (pdf)
  • Memo on Snohomish River FIS revisions (pdf)

 Flood Hazard Management Plans

• Sauk River Flood/Erosion Hazard Management Plan
• Snohomish River Comprehensive Flood Control Management Plan
• Stillaguamish River Comprehensive Flood Hazard Management Plan
• North Creek Comprehensive Flood Hazard Management Plan - Draft report to be updated to incorporate ESA (Endangered Species Act) requirements.
• Skykomish Comprehensive Flood Hazard Management Plan - Draft report to be updated to incorporate ESA (Endangered Species Act) requirements.
• Snohomish County Natural Hazards Mitigation Plan (SCNHMP) - The SCNHMP addresses nine types of natural disasters (including flooding) that could occur in Snohomish County, assessing risk levels and proposing mitigation actions to minimize damage. The Plan was updated and adopted in September 2010.

 Contacts

Chris Nelson, Hydraulic Engineer, 425-388-3464, ext. 4696 
Bob Aldrich, Project Specialist, 425-388-6424 
Michael Smith, Stream Gaging Technician, 425-388-3464, ext. 4618 
Rick Vining, Engineering Technician, 425-388-3464, ext. 4558 
Mary Hurner, Senior Planner, 425-388-6401 

PDF document links can be viewed using Adobe Acrobat Reader. To download the latest version of this program, view the instructions on this Web site.