First Advisor
Kelly Gleason
Term of Graduation
January 2026
Date of Publication
6-1-2026
Document Type
Thesis
Language
English
Subjects
Climate Change, Forest Fire, Oregon, Snow Albedo Decay, Snow Water Equivalent, SnowModel
Physical Description
1 online resource ( pages)
Abstract
Forest fire and climate change are reshaping the snow hydrology of the Pacific Northwest of the United States, yet the combined effects of these disturbances on snow accumulation, storage, and melt timing remain poorly quantified in these Mediterranean mountain watersheds. This study integrates field-based snow and radiation observations with physically based modelling to evaluate how postfire forest structure, postfire snow albedo decay, and future climate change influence snow-water storage in the Breitenbush watershed of the western Oregon Cascades. This work was conducted as part of a broader U.S. Army Corps of Engineers effort to improve postfire hydrologic prediction and flood risk assessment in burned forested watersheds.SnowModel, a distributed snow evolution model, was calibrated using in-situ micrometeorological data from the Roaring Creek watershed (a sub-basin of the Breitenbush watershed), where high-severity burned forest sites were instrumented across an elevation gradient (1,188-1,494 m). Postfire field observations indicated rapid snow albedo decay during the ablation season, which was incorporated into the model to improve the default static snow albedo parameterization. Incorporation of representative burned forest structural parameters and an empirically derived postfire snow albedo decay function, substantially improved model performance, reducing mean snow-water equivalent (SWE) error by approximately 70% relative to the default SnowModel configuration when evaluated using locally observed meteorological forcing. Simulations across current and future climate scenarios, based on shared socioeconomic pathways 3-7.0 projections from the Seventh Oregon Climate Assessment, indicate that burned forest conditions are associated with earlier snow disappearance dates and reduced snow-water storage under both current and projected climates. Under current climate conditions, burned forests exhibited 7-16% lower total snow-water storage and snow disappearance dates that were 2-6 days earlier relative to unburned forest simulations. Mid- and end-century warming scenarios further amplified these responses, reducing total snow-water storage by approximately 80-99% relative to current postfire conditions and advancing seasonal melt-out by 2-9 weeks. Hypsometric analysis of simulated snowpacks showed that future persistent snow-covered areas shift upslope by approximately 270 m relative to present conditions. Projected precipitation increases partially offset warming driven snow-water storage losses by 3% but were insufficient to restore peak SWE, April 1 SWE, or melt timing to present day postfire conditions. Together, these results indicate that forest fire disturbance and climate warming may act together to accelerate snowpack loss, shorten snow duration, and compress the elevational range of snowpack headwater storage. By integrating field observations to improve postfire process-based modelling, this study advances predictive understanding of postfire snow dynamics and provides a transferable framework for improving hydrologic forecasting in burned forest, snow-dependent mountain watersheds across the Pacific Northwest.
Rights
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Recommended Citation
Vigil, Joseph D., "Modeling the Combined Effects of Forest fire and Climate Change on Snow-Water Storage in the Oregon Cascades" (2026). Dissertations and Theses. Paper 7106.