Several houses have been evacuated after a landslide on Mercer Island in Washington State on the evening of Tuesday 8 December 2015. One home has been partially undermined by the event, with debris falling onto a property bellow, neighbouring properties have also been evacuated as a precaution. The incident happened amid heavy rainfall that has caused flooding across parts of Washington and Oregon States. Landslides
are a common problem after severe weather events, as excess pore water
pressure can overcome cohesion in soil and sediments, allowing them to
flow like liquids. Approximately 90% of all landslides are caused by
heavy rainfall.
The scene of the 8 December 2015 Mercer Island landslide. KOMO News Network.
The flooding may be linked to the El Niño weather system
currently affecting the Pacific Ocean, a phenomenon that typically
brings unseasonably warm weather to the northwest United States, starting
around the beginning of December, although this year parts of the US have been
suffering floods since the middle of October. The relationship between the two events is difficult to determine; more storms would be expected in the east Pacific late in the year
during El Niño periods, but it is not possible to say that any
particular storm was directly caused by the weather pattern.
Predicted changes to North American weather patterns during an El Niño event. NWS/NCEP Climate Prediction Center/NOAA.
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