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Barb Graff, Director

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Landslide

Landslides are common in Seattle. Late winter and early spring are the most common times for slides, with most of the documented slides in Seattle occurring in January. Nearly all landslides in Seattle result when excess water is involved, and the majority of landslides also involve human factors of some type.

The probability of a slide event rises after a wet, cold winter, especially if a freeze occurs in late winter and early spring. The ground becomes saturated over the winter, and then porous following a freeze, so a subsequent rain will penetrate the surface while the high water table will prevent the ground from absorbing it. The water increases the slope stress by adding weight and increasing pore pressure within the soil.

Major Incidents

Year

Locations

Impacts

1997

Magnolia, West Seattle

Over 100 slides reported over several days in January after a large snowfall. More occur in March.

1994

Magnolia

A large slump along Perkins Lane in Magnolia destroys five homes

1983

Queen Anne

Queen Anne slide closes Aurora for a day. Mud travels as far as Lake Union

1974

West Seattle, Golden Gardens

West Seattle experiences multiple slides in the winter. Golden Gardens Park area was also damaged.

1972

Madrona

Slides destroy homes in Madrona causing about $1.8 million in damage. These slides were also probably connected with snowfall.

1969

Magnolia

Large slides occur on Magnolia Bluff.

1961

City-wide

Slides occur in many areas of the city during the spring.

1950

City-wide

Many slides occurred in the spring. They may have been connected with heavy snowfall.

1934

City-wide

More than 400 Seattleites battle slides in ten areas of the city. These slides prompted numerous repair projects.

Issues to Note

Over 1,511 landslides have occurred in Seattle dating back to 1890. Seattle's landslide prone areas have been studied. They comprise 8.4% of the City.

The City of Seattle has adopted special land use regulations as part of its Critical Areas Ordinance. The United States Geological Survey and a private firm recently completed a new map that more accurately predicts the probability of landslides across the city.

On the Web

Environmentally Critical Areas Ordinance - Steep Slopes

Seattle Landslide Study


During an emergency, go to www.seattle.gov for the latest information.


Emergency:
Dial 911
Non-Emergency Police:
206-625-5011
Non-Emergency Fire:
206-386-1400


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