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College

College of Science and Engineering

Major

Environmental Science

Faculty Mentor

Se-Yeun Lee, PhD

Faculty Editor

Lyn Gualtieri, PhD

Student Editor

Joanna Corpuz

Abstract

Within the Upper Skagit River, the Ross, Diablo, and Gorge dams are operated by Seattle City Light for hydropower generation, flood risk reduction, fish management, and recreational opportunities. The Skagit Climate Science Consortium (SC2) study projects how streamflow will change with a warming climate under RCPs 4.5 and 8.5. The main issue identified with the SC2 study is that some model outputs are inconsistent with previous research. The objective of this study is to identify the reason(s) for the shifts in climate change impacts on flood projection in the SC2 study. This study checks whether valid data was used within the SC2 study, validates model results, recalculates flood statistics for various return frequencies, and identifies the changes in the annual peak flow dates of the occurrence. This study found that the SC2 study used data based on calendar years and calculated flood statistics with Log-Pearson III using non-bias-corrected data, resulting in lower future flood risks as compared to historical risks. By using bias-corrected data, water years, and GEV-L moments, which fit annual peak data better than Log-Pearson III, results show that flood risks will increase throughout the 21st century and will be higher than historical flood risks for time periods 2025-2074 and 2050-2099, especially under RCP 8.5. This study found that peak flows will occur earlier throughout the 21st century, which is consistent with results from previous studies. This study will be used in the process of relicensing the Skagit Hydroelectric project.

Appendices

Appendices associated with this article are available for download: Future Peak Streamflow Analytics for the Skagit River - Appendices

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