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Landslides
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 1,326 landslides have occurred in Seattle dating back to 1890. Landslides occur in approximately 1% of Seattle, primarily near the edges of steep and predominantly linear hills.
Landslide prone areas have been mapped. 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
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