Probabilistic assessment of precipitation-triggered landslides using historical records of landslide occurrence, Seattle, Washington

Environmental & Engineering Geoscience
By: , and 

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Abstract

Ninety years of historical landslide records were used as input to the Poisson and binomial probability models. Results from these models show that, for precipitation-triggered landslides, approximately 9 percent of the area of Seattle has annual exceedance probabilities of 1 percent or greater. Application of the Poisson model for estimating the future occurrence of individual landslides results in a worst-case scenario map, with a maximum annual exceedance probability of 25 percent on a hillslope near Duwamish Head in West Seattle. Application of the binomial model for estimating the future occurrence of a year with one or more landslides results in a map with a maximum annual exceedance probability of 17 percent (also near Duwamish Head). Slope and geology both play a role in localizing the occurrence of landslides in Seattle. A positive correlation exists between slope and mean exceedance probability, with probability tending to increase as slope increases. Sixty-four percent of all historical landslide locations are within 150 m (500 ft, horizontal distance) of the Esperance Sand/Lawton Clay contact, but within this zone, no positive or negative correlation exists between exceedance probability and distance to the contact.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Probabilistic assessment of precipitation-triggered landslides using historical records of landslide occurrence, Seattle, Washington
Series title Environmental & Engineering Geoscience
DOI 10.2113/10.2.103
Volume 10
Issue 2
Year Published 2004
Language English
Publisher GSW
Contributing office(s) Geologic Hazards Science Center
Description 20 p.
First page 103
Last page 122
Country United States
State Washington
County King County
City Seattle
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