An earthquake is caused by the breaking and shifting of rock beneath the Earth's surface. Ground shaking from earthquakes can collapse buildings and bridges; disrupt gas, electric, and phone service; and sometimes trigger landslides, avalanches, flash floods, fires, and huge, destructive ocean waves (tsunamis). FEMA
The chances of experiencing an earthquake in Grays Harbor County are high.
- The county is vulnerable to shallow/crustal, deep/intraplate, and subduction zone earthquakes.
- 40% to 50% of a 5.0 or better in the next 50 years
- 12% to 15% of a 7.0 or better in the next 50 years
- The major quake threat for Grays Harbor County is from the Cascadia Subduction Zone.
Floods are one of the most common hazards in the United States. Overland flooding occurs outside a defined river or stream, such as when a levee is breached. Flooding can also occur when a dam breaks, producing effects similar to flash floods. FEMA
Flooding in Grays Harbor is common.
The Chehalis & Satsop Rivers flood every 2 to 5 years. There are approximately 607 National Flood Insurance Policies in rural Grays Harbor.
Grays Harbor has 19 repetitive loss buildings which have had an average claim of $23,859 and are located in the following areas:
- Wynoochee Tracts
- Geissler Road
- Satsop Riviera
- Monte-Elma Road near Brady
- Humptulips Dike Road
- Walker Bottom
A severe storm is defined as an atmospheric disturbance featuring sustained strong winds of 40 mph or greater and/or significant precipitation such as rain or snow that can pose risks to life or property and those that require the attention of authorities. FEMA
Grays Harbor County has had six declared disasters since 2005 that included severe storms.
- Usually countywide in extent
- Heavy wind, snow, rain, ice
- County has 170% chance of 1 high wind event annually
- County has 40% chance of 1 winter storm event every two years
- Severe storm events nearly always happen with flood event
Landslides develop when water rapidly accumulates in the ground, during heavy rainfall or rapid snowmelt, changing the earth into a flowing river of mud or “slurry.” They can flow rapidly, striking with little or no warning at avalanche speeds, growing in size as they pick up trees, boulders, cars, and other materials. FEMA
Landslides can happen due to earthquakes, but most often associated with weather-related events such as rain.
- Primary type of landslides here are debris and earth flows
- Can happen on any disturbed, moderate slope with saturated soils, ocean bluffs
- Predictability of landslides difficult – depended on variety of factors
Tornadoes are nature’s most violent storms. Spawned from powerful thunderstorms, tornadoes can cause fatalities and devastate a neighborhood in seconds. FEMA
Tornados are rare in Grays Harbor County which has had two events. There is only a 5% chance of a tornado every 20 years.
Tsunamis are a series of enormous waves created by an underwater disturbance such as an earthquake, landslide, volcanic eruption, or meteorite. A tsunami can move hundreds of miles per hour in the open ocean and smash into land with waves as high as 100 feet. FEMA
- Local source tsunamis cause greater damage than distance source
- Cascadia Subduction Zone earthquake of 8 M can reach shore in 30 minutes and generate waves 30 feet tall
- Flooding can occur before the first wave crest
- There can be multiple waves over a period of hours
- The biggest wave is not always the first
Hazardous materials come in the form of explosives, flammable and combustible substances, poisons, and radioactive materials. These substances are most often released as a result of transportation accidents or because of chemical accidents in plants. FEMA
Fixed facilities: buildings or stationary structures on a single site that manufacture, produce, transfer, use store, supply or distribute materials.
- 57 facilities in the county, 21 in unincorporated areas
- 157 different chemicals
- Materials used in homes, businesses, industry, and transportation
- US 101, SR 12, SR 8, SR 105
- Spills along highways usually result from faulty equipment that cause leaks or spills, collisions, or crashes caused by human error
- Many of these roadways are near creeks, rivers, and marine waters
- PS&P Railway (RailAmerica, Inc.)
- 150 miles of track
- Centralia – Hoquiam – Bremerton (includes Naval facilities)
- Has extensive emergency response plan
- Port of Grays Harbor, other delivery points in estuary/ mouth of Chehalis
- Vessel traffic lanes along coast
- No data base on international marine transportation
- Weather, collisions, equipment failures, and operator error the cause of accidents
Volcanic eruptions can be quiet or explosive; there may be lava flows, flattened landscapes, poisonous gases, and flying rock and ash. They can be accompanied by other natural hazards, including earthquakes, mudflows and flash floods, rock falls and landslides, acid rain, fire, and tsunamis. FEMA
- No volcanoes in the county, but nearby in the Cascades
- Impact is primarily ash
- Mt St Helens May 25th eruption brought ¼ to ¾ inch of ash
The threat of wildland fires for people living near wildland areas or using recreational facilities in wilderness areas is real. Dry conditions at various times of the year and in various parts of the United States greatly increase the potential for wildland fires. FEMA
Unusual events in Grays Harbor County
- 4 factors: available fuel, moisture, terrain, and ignition source
- Strong, dry easterly winds in late summer, early fall
- Forests, beach dunes
- Last big event was in 1951 near Grayland