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A prototype system for forecasting landslides in the Seattle, Washington area

Alan F. Chleborad, Rex L. Baum, Jonathan W. Godt and Phillip S. Powers
A prototype system for forecasting landslides in the Seattle, Washington area (in Landslides and engineering geology of the Seattle, Washington area, Rex L. Baum (editor), Jonathan W. Godt (editor) and Lynn M. Highland (editor))
Reviews in Engineering Geology (2008) 20: 103-120

Abstract

Empirical rainfall thresholds and related information form the basis of a prototype system for forecasting landslides in the Seattle area. The forecasts are tied to four alert levels, and a decision tree guides the use of thresholds to determine the appropriate level. From analysis of historical landslide data, we developed a formula for a cumulative rainfall threshold (CT), P (sub 3) = 88.9-0.67P (sub 15) , defined by rainfall amounts in millimeters during consecutive 3 d (72 h) periods, P (sub 3) , and the 15 d (360 h) period before P (sub 3) , P (sub 15) . The variable CT captures more than 90% of historical events of three or more landslides in 1 d and 3 d periods recorded from 1978 to 2003. However, the low probability of landslide occurrence on a day when the CT is exceeded at one or more rain gauges (8.4%) justifies a low-level of alert for possible landslide occurrence, but it does trigger more vigilant monitoring of rainfall and soil wetness. Exceedance of a rainfall intensity-duration threshold I = 82.73D (super -1.13) , for intensity, I (mm/hr), and duration, D (hr), corresponds to a higher probability of landslide occurrence (30%) and forms the basis for issuing warnings of impending, widespread occurrence of landslides. Information about the area of exceedance and soil wetness can be used to increase the certainty of landslide forecasts (probabilities as great as 71%). Automated analysis of real-time rainfall and subsurface water data and digital quantitative precipitation forecasts are needed to fully implement a warning system based on the two thresholds.


ISSN: 0080-2018
EISSN: 2169-799X
Coden: GAEGA4
Serial Title: Reviews in Engineering Geology
Serial Volume: 20
Title: A prototype system for forecasting landslides in the Seattle, Washington area
Title: Landslides and engineering geology of the Seattle, Washington area
Author(s): Chleborad, Alan F.Baum, Rex L.Godt, Jonathan W.Powers, Phillip S.
Author(s): Baum, Rex L.editor
Author(s): Godt, Jonathan W.editor
Author(s): Highland, Lynn M.editor
Affiliation: U. S. Geological Survey, United States
Affiliation: U. S. Geological Survey, Denver, CO, United States
Pages: 103-120
Published: 2008
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 38
Accession Number: 2009-038121
Categories: Engineering geologyEnvironmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch maps
N47°06'00" - N47°46'00", W122°32'60" - W121°04'60"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200921
Program Name: USGSOPNon-USGS publications with USGS authors
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