Heavy Rainfall to Increase Lower Chehalis Valley Landslide Risk, Weather Service Warns


The National Weather Service (NWS) issued a weather advisory on Tuesday warning of a coastal storm this week, which will bring heavy rain and winds, increasing the possibility of landslides.

Areas covered by the advisory include mostly coastal communities, including the Lower Chehalis River Basin, which ends in Grays Harbor, as well as Tacoma, Bremerton, Seattle and Hood Canal.

Rainfall between 6 to 8 inches over the Olympics is expected from Thursday to Saturday.

“This amount of rain will raise the soil moisture to high levels and put extra pressure on soil instability, leading to an increased threat of landslides,” the statement read.

NWS also warned of increased chances of river floods nearer to the coast into the weekend after Thursday was set to bring large waves, rain and heavy wind throughout the day and into the evening.

While Lewis County’s two major rivers, the Chehalis and Cowlitz, were not forecast to flood, the area is still likely to receive high winds and rainfall through the weekend.

For more information about current conditions and USGS landslide indices, visit www.weather.gov/seattle, select Hydrology, and scroll down for the links to the landslide information pages.

For more information on landslides, visit the website for the Department of Natural Resources landslide geologic hazards at: http://bit.ly/2mtA3wn