Kinematics of the Swift Creek Landslide, Northwest Washington

Author

Alexander Scott McKenzie-Johnson, Western Washington University

Date Permissions Signed

5-26-2018

Date of Award

Winter 2004

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Clark, Douglas H., 1961-

Second Advisor

Crider, Juliet G.

Third Advisor

Linneman, Scott

Abstract

Deep-seated landslides significantly influence mountain landscapes in Washington State, yet relatively few of these landslides have been studied in detail. I selected the Swift Creek landslide, a large (approximately 5.489 x 10⁵ m² [54.89 hectares]), deep-seated landslide located on Sumas Mountain in northwest Washington, to be the site of a detailed study. This study, the first phase in a planned long-term study to be conducted by WWU, consisted of a detailed topographic survey, geomorphic mapping, repeated GPS surveying of monitoring points (consisting of six surveys from July 2002 to June 2003), tree-core analysis (dendrogeomorphology), and historic aerial photograph analysis.

The landslide is most likely rooted in altered ultramafites, primarily consisting of serpentinite at the surface, and closely resembles a large earthflow (even though the underlying material is bedrock). The landslide is failing by rotational movement at the head of the landslide, transitioning to a flow toward the toe of the landslide. The toe of the landslide is almost completely devoid of vegetation (most likely because of the presence of serpentinitic soils and the high activity of the landslide), and is the site of frequent failures during the winter.

Horizontal movement of monitoring points on the landslide varied from 37 m to less than the 95% horizontal precision of the GPS survey (generally less than 2 meters) during the course of this study (July 2002 to June 2003). The greatest amount of movement was observed on the toe. Rapid movement of points on the toe (>10m annually for many of the points) is related to shallow mass wasting caused by intense rain fall. Points upslope from the toe generally movedphotographs, geomorphic activity on the landslide increased to a maximum in the 1970s and has slightly diminished since that time. Aerial photographs and a comparison between topographic data from 1972 and 2002 indicate that the toe of the landslide has enlarged steadily in both thickness and horizontal extent since the initiation of the landslide and continues to enlarge.

Type

Text

Keywords

Deep-seated landslides, Sumas Mountain

Publisher

Western Washington University

OCLC Number

1060584730

Subject – LCSH

Landslides--Washington (State)--Swift Creek (Whatcom County); Geomorphology--Washington (State)--Swift Creek (Whatcom County); Earth movements--Washington (State)--Swift Creek (Whatcom County)

Geographic Coverage

Swift Creek (Whatcom County, Wash.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

Recommended Citation

McKenzie-Johnson, Alexander Scott, "Kinematics of the Swift Creek Landslide, Northwest Washington" (2004). WWU Graduate School Collection. 790.
https://cedar.wwu.edu/wwuet/790