Washington Statewide Rule

Washington Floodplain Management Statewide Standards

Heavy RestrictionsApplies statewide across Washington (2026)

Key Facts

Authority: Department of Ecology
Elevation Standard: 1 foot above BFE
Floodway Fill: Generally prohibited
Statute: RCW 86.16

Last verified: September 5, 2026Source: Washington State Legislature

Summary

Washington requires all communities participating in the National Flood Insurance Program to adopt floodplain ordinances meeting state minimum standards under RCW 86.16.

(1) Beginning July 26, 1987, every county and incorporated city and town shall submit to the department of ecology any new floodplain management ordinance or amendment to any existing floodplain management ordinance. Such ordinance or amendment shall take effect 30 days from filing with the department unless the department disapproves such ordinance or amendment within that time period.

Source: Washington State LegislatureView official code

Full Breakdown

RCW 86.16 grants the Department of Ecology authority to regulate floodplain development statewide. All Washington counties and cities with mapped flood hazard areas must adopt floodplain management ordinances meeting NFIP and state minimum standards, including elevation of new structures one foot above the base flood elevation (BFE), prohibition of fill in floodways, and special review for critical facilities. RCW 86.16.041 authorizes Ecology to review and approve local floodplain ordinances. The 2017 update extended Endangered Species Act consistency requirements for floodplain development affecting salmon habitat. Local jurisdictions may impose stricter standards.

Violations & Penalties

Building or filling in regulated floodways without permits can result in civil penalties, mandatory removal, loss of NFIP eligibility for the community, and personal liability for damage to neighboring properties.

Frequently Asked Questions

Can I build a house in a Washington FEMA floodplain?

Yes, in the flood fringe with proper elevation and permits, but new residential construction is prohibited in regulated floodways under most local ordinances and RCW 86.16 standards.

How high must my home be elevated in a Washington flood zone?

Washington requires the lowest floor including basement to be at least one foot above base flood elevation, exceeding the NFIP minimum of at-grade BFE for new and substantially improved structures.

Sources

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