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Precipitation thresholds for landslide occurrence near Seattle, Mukilteo, and Everett, Washington

Open-File Report 2017-1039
Prepared in cooperation with Sound Transit
By: , , , and 
https://doi.org/10.3133/ofr20171039

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Abstract

Shallow landslides along coastal bluffs frequently occur in the railway corridor between Seattle and Everett, Washington. These slides disrupt passenger rail service, both because of required track maintenance and because the railroad owner, Burlington Northern Santa Fe Railway, does not allow passenger travel for 48 hours after a disruptive landslide. Sound Transit, which operates commuter trains in the corridor, is interested in a decision-making tool to help preemptively cancel passenger railway service in dangerous conditions and reallocate resources to alternative transportation.

Statistical analysis showed that a majority of landslides along the Seattle-Everett Corridor are strongly correlated with antecedent rainfall, but that 21-37 percent of recorded landslide dates experienced less than 1 inch of precipitation in the 3 days preceding the landslide and less than 4 inches of rain in the 15 days prior to the preceding 3 days. We developed two empirical thresholds to identify precipitation conditions correlated with landslide occurrence. The two thresholds are defined as P3 = 2.16-0.44P15 and P3 = 2.16-0.22P32, where P3 is the cumulative precipitation in the 3 days prior to the considered date and P15 or P32 is the cumulative precipitation in the 15 days or 32 days prior to P3 (all measurements given in inches). The two thresholds, when compared to a previously developed threshold, quantitatively improve the prediction rate.

We also investigated rainfall intensity-duration (ID) thresholds to determine whether revision would improve identification of moderate-intensity, landslide-producing storms. New, optimized ID thresholds evaluate rainstorms lasting at least 12 hours and identify landslide-inducing storms that were typically missed by previously published ID thresholds. The main advantage of the ID thresholds appears when they are combined with recent-antecedent thresholds because rainfall conditions that exceed both threshold types are more likely to induce two or more landslides than conditions that exceed only one threshold type.

Suggested Citation

Scheevel, C.R., Baum, R.L., Mirus, B.B., and Smith, J.B., 2017, Precipitation thresholds for landslide occurrence near Seattle, Mukilteo, and Everett, Washington: U.S. Geological Survey Open-File Report 2017–1039, 51 p., https://doi.org/10.3133/ofr20171039.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Materials and Methods
  • Results
  • Discussion
  • Conclusions
  • Acknowledgments
  • References Cited
  • Appendix 1. Landslide Date Inventories
  • Appendix 2. Intensity-Duration Threshold Conditions
  • Appendix 3. Support Figures for Everett and Mukilteo Datasets
Publication type Report
Publication Subtype USGS Numbered Series
Title Precipitation thresholds for landslide occurrence near Seattle, Mukilteo, and Everett, Washington
Series title Open-File Report
Series number 2017-1039
DOI 10.3133/ofr20171039
Year Published 2017
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Geologic Hazards Science Center
Description vi, 51 p.
Country United States
State Washington
City Everett, Mukilteo, Seattle
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details