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Date Permissions Signed

11-19-2018

Date of Award

Fall 2018

Document Type

Masters Thesis

Department or Program Affiliation

Geology

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Mitchell, Robert J. (Geologist)

Second Advisor

Clark, Douglas H., 1961-

Third Advisor

Grossman, Eric E.

Abstract

The Nooksack River in Whatcom County, Washington­ is an essential fresh water resource for industry, agriculture, municipalities and serves as vital fish habitat. Like many mountainous watersheds in the western Cascades, the Nooksack Basin is susceptible to shallow mass wasting and debris flows because of its steep slopes, young glaciated terrain, and storms with high intensity precipitation. Understanding how projected reductions in snowpack and increased winter rainfall will affect mass-wasting susceptibility in the Nooksack basin is important, because sediment produced mass wasting will jeopardize valuable aquatic and fish habitat, increase flooding risk in the Nooksack River, and affect estuarine and coastal dynamics.

With a projected 60% decrease in snowpack and increase in the snowline elevation by the 2075 climate normal, there will be an increase in exposed forest roads, harvestable forest areas, and previously mapped landsides, which are all documented to increase sediment delivery to streams. Retreating glaciers will produce at least 2 km2 of exposed moraines, which have the potential to erode, fail and provide additional sediment to streams, especially during large storm events coinciding with minimum snowpack during the fall and early spring seasons. I applied a static infinite-slope ArcGIS model and a dynamic, probabilistic mass-wasting model integrated into the Distributed Hydrology Soil Vegetation Model (DHSVM) to the Nooksack River watershed to determine areas susceptible to mass wasting into the 21st century. Susceptibility maps produced by the models indicate an increase in regions susceptible to slope failure during the winter months in snow free areas at higher elevations later in the 21st century. Slope failure susceptibility increased with soil saturation, which is anticipated with higher intense winter rainfall events. Slopes greater than about 30o with thick regolith deposits and lower soil mechanical strength, e.g., sand, loamy sand, sandy loam, silt, moraines, glacial outwash and former landslide deposits were correlated with higher mass-wasting susceptibility. The simpler static ArcGIS infinite-slope model yielded comparable results to the more complex probabilistic method integrated into the DHSVM for identifying areas susceptible to mass wasting.

Type

Text

Keywords

Modeling, landslide, infinite slope, sediment, factor of safety

Publisher

Western Washington University

OCLC Number

1079065909

Subject – LCSH

Climatic changes--Washington (State); Mass-wasting--Washington (State)--Nooksack River; Slopes (Soil mechanics)--Washington (State)--Nooksack River--Stability; Sediment control--Washington (State)--Nooksack River

Geographic Coverage

Nooksack River (Wash.); Washington (State)

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.

Rights Statement

http://rightsstatements.org/vocab/InC-EDU/1.0/

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

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