Stream channel, plus floodplain areas, that must be kept free from building so the 1% annual chance of flood can occur without increasing flood heights. If you have questions about the flood map updates, please contact the River and Floodplain Management Section at 206-477-4727 or firstname.lastname@example.org.
A COMA establishes a property's location in relation to the Special Flood Hazard Area (FHA). Lamas are usually issued because a property has been inadvertently mapped as being in the floodplain, but is actually on natural high ground above the base flood elevation.
A Letter of Map Revision Based on Fill (LORD) is FEMA's modification of the Special Flood Hazard Area (FHA) shown on the Flood Insurance Rate Map (FIRM) based on the placement of fill outside the existing regulatory flood way. All development in a mapped floodplain needs a permit, and buildings, in particular, must demonstrate compliance with King County Code.
Managing development in floodplains is a core responsibility of King County as part of our participation in the National Flood Insurance Program. Proper permitting means that flood insurance will remain available to all residents of unincorporated King County.
Floodplain development standards are part of the Critical Areas chapter of King County Code 21A.24. Sections 21A.24.230 through 21A.24.272 establish the requirements for floodplains, including coastal high hazard areas.
All buildings must have a FEMA Elevation Certificate completed by a licensed surveyor that shows compliance with the King County Code. On this page you learn what types of flooding are typical in Washington and how do you protect yourself, your family and your home.
Finally, you'll find links to NEWS offices that provide forecast and safety information for Washington, as well as links to our partners who play a significant role in keeping you safe Elsewhere in the Columbia Basin, the flood destroyed 5,000 homes, forced some 50,000 people to evacuate and caused an estimated $100 million in damage. In Washington, flooding occurred in Vancouver, Panama, Woodland, Longview, Kennewick, and Richland.
At the Vancouver river gauge, the Columbia crested on June 13-14 at 31.0 feet above sea level. The flow at the Method River, which surpassed its flood stage level of 10 feet, and rose to 12.30.
The flow at the Dalles' river Gage crested at 1 million cubic feet per second (CFS). Photo by Robles L. Johnson, Courtesy U.S. Department of Energy Columbia River Flood near Washout River and Namaste February 1996 flood was one of the most widespread across the whole Pacific Northwest and Washington : 24 of 39 Washington State counties were affected.
A precursor to the event was an extended period of cold temperatures that brought snow to low elevations and created river ice on the east side of the Cascades. In addition to record precipitation in some mountainous areas, melting snowpack across the region contributed as much as half of the total runoff in some locations. The heavy rain and rapid Snowbelt combined to produce record and near-record flooding, mudslides, and avalanches.
More than 2,600 homes were flooded, dozens of bridges were lost, an estimated $120 million in damages, and 3 fatalities occurred in Washington. The affected counties were Adams, Austin, Benton, Clark, Columbia, Cowling, Garfield, Grays Harbor, King, Kit sap, Hittites, Kickiest, Lewis, Lincoln, Pierce, Skagit, Ska mania, Snohomish, Spokane, Thurston, Wahkiakum, Wall Wall, Whitman and Yakima.
This storm, fueled in part from sub-tropical moisture associated with former western Pacific Typhoon Cimarron, produced rain amounts of between 10 and 38 inches in the Cascades and Olympics and 4 to 10 inches in western Washington lowlands during this period. The mountains had little if any snow pack, so the floods were driven solely by the heavy rainfall amounts. Stampede Pass in the central Washington Cascades received an all-time daily record rain total of 8.22 inches on Nov 6, breaking the old record of 7.29 inches set on Nov 19, 1962.
In all, 15 western Washington rivers reached all-time record flood crest levels. The Skagit River at Concrete reached 39.79 ft. or 145,000 CFS, which was only the seventh the highest level in the post-dam era, but nearly 15 ft. above flood stage.
Photo courtesy of Lewis CountySatellite view of water vapor plume showing Atmospheric River (aka ” Pineapple Express”) A series of three storms moved through the Pacific Northwest from Saturday, December 1st, through Monday, December 3, 2007. On December 1, a rather cold air mass was in place over Washington that was being maintained by a northerly jet stream plunging southward from Alaska and Canada, resulting in lowland snow.
It brought tremendous waves, hurricane force winds to the coast for more than 30 hours, and torrential rain to both the lowlands and mountainous areas. That storm was fueled by tropical moisture from the remnants of western Pacific Ocean Typhoons Hag ibis and Mi tag.
Record flooding occurred on the Chevalier, Snohomish, Alpha, and Willa pa Rivers. Significant and damaging urban and small stream flooding occurred in Snohomish, King, Lewis, Thurston, Mason, and Kit sap counties when 3 to 8 inches of rain fell over the area.
Willa pa Hills and southern Olympic mountain areas measured 10 to 20 inches. A landslide hit a house and buried a man in his sleep near Hood sport in Mason County.
In the headwaters of the Chevalier River, flash flood conditions occurred and whole herds of livestock were lost. A portion of Interstate 5, the major thoroughfare between Portland and Seattle, was covered by 10 feet of water.
The extreme rainfall also produced more than 2000 large landslides/debris flows causing additional damages and injuries. WSD OT photo by Jim Cult. Little Bear Creek claims a car as it overtops Washington State Route 522 near Joinville.
The strong westerly winds aloft enhanced precipitation amounts in the mountains. Record flooding occurred on the Snoqualmie, Told, North Fork Stillaguamish, and Nacelle Rivers.
Ice jam flooding was a problem along Hangman Creek in Spokane County. Â Highly unstable mountain snowpack produced numerous avalanches.
Numerous highways and local roadways were closed by landslides and mudslides and several dozen homes and structures were impacted. One landslide at Yak near Interstate-90 knocked down ski lift towers and damaged several homes and buildings.
Over 44,000 people were evacuated as a result of rising or high water as well as over 1500 landslides across the state. A mudslide covers Highway 542 near Deming, Wash. (Photo courtesy of WSD OT)January 2009 flooding aerial view.
Flash flooding is a rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (i.e., intense rainfall, dam failure, ice jam). At any time of year, a storm from over the ocean can bring heavy precipitation to the U.S. coasts.
Wildfires burn away the vegetation of an area, leaving behind bare ground that tends to repel water. When rain falls, it runs off a burn scar towards a low-lying area, sometimes carrying branches, soil and other debris along with it.
Without vegetation to hold the soil in place, flooding can produce mud and debris flows. A back-up of water into surrounding areas can occur when a river or stream is blocked by a build-up of ice or other debris.
Flooding due to Snowbelt most often occurs in the spring when rapidly warming temperatures quickly melt the snow. The water runs off the already saturated ground into nearby streams and rivers, causing them to rapidly rise and, in some cases, overflow their banks.
We work to reduce life and property losses, and protect the environmental functions that floodplains offer. In Western Washington, floods typically result from prolonged winter rains.
In Eastern Washington and in the Cascades, spring Snowbelt and rain-on-snow events are the primary causes of flooding. We are working to carry out a collaborative effort to reduce flood damage and restore aquatic habitat in the Chevalier River basin.
This partnership of local governments, state and federal agencies, and private organizations works to coordinate multi-benefit projects that reduce flood hazards and restore the natural functions of the floodplain. We work in partnership with FEMA to run the Risk MAP program in Washington.
This program delivers high-quality data, risk assessment tools, and mitigation expertise to local and tribal governments and communities to reduce risks from natural hazards, including floods, earthquakes, wildfires, and landslides. Our Risk MAP app shows current Washington projects and effective flood hazard maps.
We have regional floodplain management staff in Spokane, Union Gap, Bellevue, and Olympia to assist communities. FEMA maintains and updates data through flood maps and risk assessments.
If you believe your property was incorrectly identified as a Special Flood Hazard Area, you may submit an application to FEMA for a formal determination and potential revision. Cooperating Technical Partners are communities, regional agencies, state agencies, universities and tribal nations that become more active participants in the FEMA flood hazard mapping program.