Washington state community devastated by mudslide could face floods

Reuters News
Posted: Oct 23, 2014 4:42 PM

By Victoria Cavaliere

SEATTLE (Reuters) - A Washington state community devastated by a mudslide that killed 43 people in March was bracing for its first rainy season since the disaster and the threat of flooding from a river that changed course as a result of it, officials said on Thursday.

A rain-soaked hillside collapsed above the north fork of the Stillaguamish River on March 22, unleashing a torrent of mud that buried a community near Oso, 55 miles (89 km) northeast of Seattle.

The risk of flooding remains a concern for hundreds of local residents, especially for those living in low-lying areas and close to the mudslide zone. The mudslide's force temporarily dammed the Stillaguamish River in one area and has changed its flow and elevation, according to scientists.

With the area entering its rainy season, an official from the U.S. Geological Survey said the agency was monitoring sediment deposits released by the mudslide that could build up and exacerbate flooding risks along the river's path.

"This is a fairly flood-prone river already and there's some big flows that come through it," U.S. Geological Survey research hydrologist Chris Magirl said.

"By filling the channel with two to four feet (0.6 meters to 1.2 meters) of new sediment, it means that any water that comes downstream, instead of staying in the channel, spills out," Magirl said.

On Wednesday, the Washington state area that includes Oso experienced heavy rainfall but the Stillaguamish River stayed below flood levels, according to the National Weather Service.

Scientists and emergency responders plan to keep a close eye on the river through the winter. The landslide zone has mostly stabilized since the disaster and the river was slowly returning to its previous elevation, Magirl said.

(Reporting by Victoria Cavaliere, Editing by Alex Dobuzinskis and Will Dunham)