Hydroclimatic conditions preceding the March 2014 Oso landslide

Journal of Hydrometeorology
By: , and 

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Abstract

The 22 March 2014 Oso landslide was one of the deadliest in U.S. history, resulting in 43 fatalities and the destruction of more than 40 structures. We examine synoptic conditions, precipitation records and soil moisture reconstructions in the days, months, and years preceding the landslide. Atmospheric reanalysis shows a period of enhanced moisture transport to the Pacific Northwest beginning on 11 February 2014. The 21- to 42-day periods prior to the landslide had anomalously high precipitation; we estimate that 300-400 mm of precipitation fell at Oso in the 21 days prior to the landslide. Relative only to historical periods ending on 22 March, the return periods of these precipitation accumulations are large (25-88 years). However, relative to the largest accumulations from any time of the year (annual maxima), return periods are more modest (2-6 years). In addition to the 21-42 days prior to the landslide, there is a secondary maximum in the precipitation return periods for the 4 years preceding the landslide. Reconstructed soil moisture was anomalously high prior to the landslide, with a return period that exceeded 40 years about a week before the event.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Hydroclimatic conditions preceding the March 2014 Oso landslide
Series title Journal of Hydrometeorology
DOI 10.1175/JHM-D-15-0008.1
Volume 16
Issue 3
Year Published 2015
Language English
Publisher American Meteorological Society
Contributing office(s) Washington Water Science Center
Description 7 p.
First page 1243
Last page 1249
Country United States
State Washington
Online Only (Y/N) N
Additional Online Files (Y/N) N