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Date Permissions Signed
Date of Award
Department or Program Affiliation
Master of Science (MS)
Mitchell, Robert J. (Geologist)
Clark, Douglas H., 1961-
Grossman, Eric E.
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.
Modeling, landslide, infinite slope, sediment, factor of safety
Western Washington University
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
Nooksack River (Wash.); Washington (State)
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Knapp, Kevin, "The Effects of Forecasted Climate Change on Mass Wasting Susceptibility in the Nooksack River Basin" (2018). WWU Graduate School Collection. 807.