The vast majority of theses in this collection are open access and freely available. There are a small number of theses that have access restricted to the WWU campus. For off-campus access to a thesis labeled "Campus Only Access," please log in here with your WWU universal ID, or talk to your librarian about requesting the restricted thesis through interlibrary loan.

Date Permissions Signed

12-7-2022

Date of Award

Fall 2022

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

Pfeiffer, Allison

Third Advisor

Mauger, Guillaume S.

Abstract

Climate change is projected to increase river flooding in the Puget Sound region of Washington State by reducing snowpack and yielding more intense storm events. Pairing meteorological forcings from general circulation models (GCMs) with a physically based hydrologic model is a robust method of assessing watershed response to projected climate. Before GCM forcings can be applied to regional hydrologic models, some form of downscaling or regionalization is required. Dynamical downscaling is a means of incorporating mesoscale atmospheric processes within GCM-informed boundary conditions. Here I apply climate projections, dynamically downscaled using the Weather Research and Forecasting model (WRF), to the Stillaguamish watershed in northwest Washington State using the physically based Distributed Hydrology Soil Vegetation Model (DHSVM). I simulate hourly streamflow for 12 high emissions scenarios (i.e., Representative Concentration Pathway 8.5) throughout the 1,724- square-kilometer basin from 1970 through 2099 and analyze climate and hydrologic trends, with a particular emphasis on peak flows. My projections indicate that as the climate warms, snowpack will recede to higher elevations and the basin will shift from transitional to raindominant, leading to an increase in average winter streamflows and a decline in spring and summer streamflows. Peak streamflow magnitude in the Stillaguamish River will increase by about +26.5% across the assessed return intervals (2 to 100 years) and flow durations (3 hours to 1 week) by the 2080s. Similarly, modern day peak flow magnitudes will recur more frequently. Flow generating mechanisms also change, with rain-on-snow events decreasing in likelihood while extreme precipitation events become more common and more severe. These shifts have wide ranging implications for flooding within the developed lowlands of the watershed, and for threatened salmonid populations which are culturally and economically critical to the region.

Type

Text

Keywords

Hydrology, Climate, Climate Change, Stillaguamish, Watershed, River, Flooding, Ecosystem, Peak Flow, Stream

Publisher

Western Washington University

OCLC Number

1368010459

Subject – LCSH

Climatic changes--Washington (State)--Stillaguamish River Watershed--Forecasting; Hydrological forecasting--Washington (State)--Stillaguamish River Watershed; Streamflow--Washington (State)--Stillaguamish River Watershed; Salmonidae--Climatic factors--Washington (State)--Stillaguamish River Watershed

Geographic Coverage

Stillaguamish River Watershed (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 document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

Rights Statement

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

Creative Commons License

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

Download

Included in

Geology Commons

Share

COinS