Numerical modeling of rainfall thresholds for shallow landsliding in the Seattle, Washington, area
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Abstract
The temporal forecasting of landslide hazard has typically relied on empirical relations between rainfall characteristics and landslide occurrence to identify conditions that may cause shallow landslides. Here, we describe an alternate, deterministic approach to define rainfall thresholds for landslide occurrence in the Seattle, Washington, area. This approach combines an infinite slope-stability model with a variably saturated flow model to determine the rainfall intensity and duration that leads to shallow failure of hillside colluvium. We examine the influence of variation in particle-size distribution on the unsaturated hydraulic properties of the colluvium by performing capillary-rise tests on glacial outwash sand and three experimental soils with increasing amounts of fine-grained material. Observations of pore-water response to rainfall collected as part of a program to monitor the near-surface hydrology of steep coastal bluffs along Puget Sound were used to test the numerical model results and in an inverse modeling procedure to determine the in situ hydraulic properties. Modeling results are given in terms of a destabilizing rainfall intensity and duration, and comparisons with empirical observations of landslide occurrence and triggering rainfall indicate that the modeling approach may be useful for forecasting landslide occurrence.
Study Area
Publication type | Article |
---|---|
Publication Subtype | Journal Article |
Title | Numerical modeling of rainfall thresholds for shallow landsliding in the Seattle, Washington, area |
Series title | Reviews in Engineering Geology |
DOI | 10.1130/2008.4020(07) |
Volume | 20 |
Year Published | 2008 |
Language | English |
Publisher | Geological Society of America |
Publisher location | Boulder, CO |
Contributing office(s) | Geologic Hazards Science Center |
Description | 16 p. |
First page | 121 |
Last page | 136 |
Country | United States |
State | Washington |
City | Seattle |
Online Only (Y/N) | N |
Additional Online Files (Y/N) | N |
Google Analytic Metrics | Metrics page |