Coastal Hazards & Extremes
Along the Pacific Northwest coast, a combination of rising sea levels, intensifying waves, changes in storm patterns, and major El Niño and La Niña events has produced increased flooding and erosion hazards for many coastal communities. At CIRC, we are examining the impacts of numerous coastal hazards and extremes while simultaneously identifying communities along the coast that are bearing the brunt of these hazards.
Planning for coastal hazards, be it the design of coastal defenses (such as sea walls) or zoning for floods, has tended to be based on historical records of maximum water levels reached during past floods. However, relying only on the observational record may significantly underestimate what areas of the Pacific Northwest coast are at risk (Serafin et al. 2014; Baron et al. 2015).
It is normal for Pacific Northwest beaches and shorelines to erode during our region’s stormy winter months as waves beat down on their surface, carrying sediment out to sea. Following the winter months, natural sediment supplies help rebuild the beaches. As our planet warms, we are likely to see not only sea level rise, but also losses in some areas of the natural sediment supply that rebuilds our beaches following winter losses (Barnard et al. 2017).
Coastal erosion across the Pacific Northwest varies widely during years with El Niño and La Niña events (Barnard et al. 2015).
In the Pacific Northwest, El Niño events have been linked to an increase in coastal erosion of roughly 50% over typical, or El Niño Southern Oscillation-neutral (ENSO-neutral) winters (Barnard et al. 2015).
La Niña events were linked to a 126% increase in coastal erosion as compared to non-El Niño/La Niña (ENSO-neutral) winters (Barnard et al. 2015).
The increased wave energy observed during both El Niño and La Niña events is the key driver of this increased erosion (Barnard et al. 2015).
The El Niño event of 2015–2016 was one of the three most powerful to date since records began in 1871 and resulted in the highest winter beach erosion on record for the West Coast (Barnard et al. 2017).
During the extreme El Niño winter of 2015–2016, Oregon beaches experienced 30% more erosion than during the El Niño-free winter of 2014–2015, which was used in the study for comparison (Barnard et al. 2017).
Barnard, Patrick L., Daniel Hoover, David M. Hubbard, Alex Snyder, Bonnie C. Ludka, Jonathan Allan, George M. Kaminsky, Peter Ruggiero, Timu W. Gallien, Laura Gabel, Diana McCandless, Heather M. Weiner, Nichola Cohn, Dylan L. Anderson, and Katherine A. Serafin. “Extreme Oceanographic Forcing and Coastal Response Due to the 2015–2016 El Niño.”
Nature Communications 8 (2017).
Barnard, Patrick L., Andrew D. Short, Mitchell D. Harley, Kristen D. Splinter,
Sean Vitousek, Ian L. Turner, Jonathan Allan, Masayuki Banno, Karin R. Bryan, André Doria, Jeff E. Hansen, Shigeru
Kato, Yoshiaki Kuriyama, Evan Randall- Goodwin, Peter Ruggiero, Ian J. Walker, and Derek K. Heathfield et al. 2015. “Coastal Vulnerability across the Pacific Dominated by El Nino/Southern Oscillation.”
Nature Geoscience 8 (10): 801–7.
Baron, Heather M., Peter Ruggiero, Nathan J. Wood, Erica L. Harris, Jonathan Allan, Paul D. Komar, and Patrick Corcoran. “Incorporating climate change and morphological uncertainty into coastal change hazard assessments.”
Natural Hazards 75, no. 3 (2015): 2081-2102.
Serafin, Katherine A., and Peter Ruggiero. “Simulating Extreme Total Water Levels Using a Time-Dependent, Extreme Value Approach.”
Journal of Geophysical Research: Oceans 119, no. 9 (2014): 6305-6329.