SEATTLE (Reuters) - A landslide that began in December has destroyed a home on an island north of Seattle and more residents have been told they could be at risk, scientists said on Monday.
About 20 homes in the landslide zone on Whidbey Island, a short ferry ride from the mainland, have received letters encouraging residents to consult engineers to determine whether a bluff behind their properties was in danger of giving way, local officials said.
The landslide began moving in late December, when one home was destroyed. Two more homes were damaged in February and are at risk of collapse. A fourth home was leveled on Friday, Island County officials said.
"It's a more active slide year than normal," said Connie Bowers, assistant engineer for Island County. "If they're full-time residents, (they) should look into having a geotechnical engineer review the property behind them for life safety."
Many of the structures near the landslide zone are vacation homes built on the shore of Puget Sound, she said, and their owners are encouraged to stay away while the landslide remains active.
"This is an old slide area. It is unsettled, and they know that," Bowers said.
Residents told local broadcaster KIRO that though the landslide was moving slowly, the destruction can be rapid.
"This happens really fast, ten seconds and bam this stuff is down," Stacie Burgua said.
Whidbey Island, home to about 58,000 people, was formed out of glacial silt and is one of many areas in Washington state known to be prone to mudslides, the state Department of Natural Resources said.
Much of the landslide risk is determined by groundwater saturation, said department spokesman Joe Smiley.
In 2013, a landslide on Whidbey Island knocked one home off its foundation and forced the evacuation of 22 others. The slide also cut off power and roads to the area.
Last year, a rain-soaked hillside collapsed near the rural community of Oso, northeast of Seattle in the foothills of the Cascade Mountains, killing 43 people. New video that emerged from the catastrophe shows waves of mud tumbling into the valley below more than 10 minutes after the hill gave way.
(Reporting by Victoria Cavaliere; Editing by Mohammad Zargham)