Preliminary Maps

Modernization Program

In the late 1990s, the Federal Emergency Management Agency (FEMA) initiated a Flood Map Modernization Program to convert the nation's existing outdated paper Flood Insurance Rate Maps (FIRMs) to a new digital format. In 2003, congress appropriated money for the project, with a goal of effectively completing digital mapping of the floodplains for 90 percent of the U.S. population by 2010.

Communities were encouraged to take an active role through the Cooperating Technical Partners (CTP) Program, which allowed qualified communities such as Snohomish County to direct selected flood hazard mapping projects themselves, using FEMA funding and standards. FEMA agreed to fund up to 75% of future flood hazard mapping efforts.


There are a number of benefits of having local communities involved in the remapping, including:

  • Flood maps are much more accurate when they include detailed local knowledge and data on floods from government offices and floodplain residents.
  • The routine collection of local flood data allows the identification of changes in flood behavior as well as the need for updated maps.
  • There is greater opportunity for public outreach and involvement throughout the project.
  • Additional hazard information can be incorporated onto the maps to increase public awareness of hazards (for instance, future flow predictions in urban areas).


Regionally, Snohomish County was a high priority for remapping efforts due to the number of floods that have occurred, the high level of damages incurred, the relatively large population base, and the high number of repetitive loss structures (homes which have been flooded more than once in a ten year period).

Snohomish County began working with FEMA and the Department of Ecology to remap the county's floodplains in 1999. The most recent updates to the Digital Flood Insurance Rate Maps (DFIRMs) were adopted by the county in June 2020.


Find the appropriate map panel number by referring to the Snohomish County Index Map (PDF). All maps are provided in Adobe Acrobat format and are very large files (possible long download time depending on your equipment).

Flood Insurance Study

Also see the accompanying Preliminary Flood Insurance Study: