NATIONAL WEATHER SERVICE - During most winters, storms bring long periods of heavy rain and snow to the Pacific Northwest. In addition to extended rain, flooding can also occur due to ice jams, where large flows of ice pile up. This pile-up of ice can act like a dam, causing water to back up and flood. Warm weather can also cause snow on the middle and higher mountains to melt, putting more water into already rain-swollen streams.
Flooding causes more deaths and prpoerty damage in the U.S. than any other severe weather related event. The majority of flood related deaths occur when people become trapped in automobiles while attempting to drive through flooded areas. Flowing water can be deceptively strong, and pack a powerful punch. As little as six inches of water is enough to float a small car and carry it away. There have been many floods in the history of the Northwest, which include the devastating floods of December 1964 and February 1996. Most recently, in Dec 2007 and Jan 2009, significant flooding struck the Pacific Northwest, closing a twenty mile stretch of interstate 5 near Chehalis Washington under 10 feet of water. Coastal flooding can also occur during the winter months, and poses a threat to life and property. Winds generated from very strong Pacific storms can drive ocean water inland, much like a storm surge, and can cause significant flooding along the immediate coastal areas and estuaries.
A Flood refers to a gradual rise in the water along a stream, river, wash or over an extended period of time. Floods result from heavy rainfall, river ice jams, snowmelt. They can erode an entire mountain side, roll boulders the size of trucks, tear out trees, destroy buildings, wash out roads and bridges, and cause the loss of lives. Rain weakened soils can also result in mudslides capable of closing major highways.
Flood Watch This means that flooding is possible with the watch area. You should remain alert and be ready to evacuate on a moment's notice.
Flood Warning This means that flooding has been reported, or is imminent. When a flood warning is issued for your area, act quickly to save yourself. If advised to evacuate, do so immediately. Go to higher ground, or climb to safetly. Move to a safe area before access is cut off by rising flood waters.
Nearly half of all flood fatalities are auto-related. Water that is two feet deep will carry away most automobiles. Never attempt to drive through a flooded roadway. The road bed may be washed out beneath the water, and you could be stranded or trapped. If the vehicle stalls, leave it immediately and seek higher ground.
The best advice if you are in a vehicle: TURN AROUND…Don't DROWN.