Coastal Hazards & Extremes

Our coastlines are increasingly becoming defined by extremes and hazards. By the end of this century, sea levels along the Pacific Northwest coast are expected to rise by anywhere from a couple of inches to roughly one-and-a-half meters (five feet) by the year 2100. This translates into the Pacific Ocean inundating our region’s shorelines horizontally by as much as 75 meters (164 feet) in some areas depending on the local geography and causing significant coastal erosion depending on local sediment budgets (i.e., how much sediment is either added or taken away from the coastline). However, given dynamic coastal processes, including erosion and beach loss, the exact level of inundation could be much higher in some areas. What is crystal clear is that rising sea levels are connected to human-made climate change. Okay, this is where simplicity takes a backseat to complexity. Hold on.

According to measurements taken using buoys and analyzed by CIRC researcher Peter Ruggiero and colleagues, sea level isn’t the only thing rising. Ocean waves along the Pacific Northwest coast have also been rising. Mean wave heights have risen by about 1.5 centimeters (about half an inch) a year, while significant wave heights—that is the really tall waves—have grown by as much as 10 cm (roughly a third of a foot) a year since the 1970s, according to a 2007 paper by Ruggiero and colleagues. These waves coupled with rising sea levels and periodic El Niño events—known to intensify waves and raise local sea levels—have led to substantial flooding and erosion along our region’s coastline. It’s unclear whether this observed trend is going to continue under climate change. This is why CIRC researchers are planning for multiple possibilities and multiple complexities.

At CIRC, we are weighing the impacts of numerous hazards and extremes while simultaneously locating communities along the coast who are bearing the brunt of these climate changes. In our work, we have seen first hand how a combination of hazards and extremes has impacted our coastal communities.

Consider Neskowin, Oregon, where CIRC researchers worked with local homeowners and planners on a Community Adaptation effort called Envision Tillamook Coastal Futures. Because of their local geography, Neskowin residents have watched as their beaches and cliffs have become a hotspot for erosion and flooding. Residents have lost roughly 70 meters (230 feet) of their beach to the Pacific Ocean between the late 1960s and early 2000s, according to CIRC and other researchers’ work.

Our efforts to track extremes in places including Neskowin have led us to develop and refine powerful computer models that can simulate the different pieces of coastal hazards and extremes—that’s wave heights, El Niños, sea level rise, and whether the tide is in or out and by how much—and then combine those simulations in ways that account for the shape of the local coastline. This gives us a clearer picture of just how extreme, given the right combination, extreme events can be; just how hazardous hazards can be. It has also given us insight into the sort of challenges our region’s coastal communities face as our climate changes.

 

Sources

Barnard, Patrick L., Jonathan Allan, Jeff E. Hansen, George M. Kaminsky, Peter Ruggiero, and André Doria. "The impact of the 2009–10 El Niño Modoki on US West Coast beaches." Geophysical Research Letters 38, no. 13 (2011).

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. doi:10.1007/s11069-014-1417-8.

Dalrymple, Robert A., L. Breaker, B. Brooks, D. Cayan, G. Griggs, W. Han, B. P. Horton et al. "Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future." National Research, Council The National Academies Press, Washington DC (2012).

Envision Tillamook County Coastal Futures Project. “ENVISION Integrated Modeling Platform.” Oregon State University, accessed December 13, 2016. http://envision.bioe.orst.edu/StudyAreas/Tillamook/.

Komar, Paul D., Jonathan C. Allan*, and Peter Ruggiero. "Sea level variations along the US Pacific Northwest coast: Tectonic and climate controls." Journal of Coastal Research 27, no. 5 (2011): 808-823. doi:10.2112/JCOASTRES-D-10-00116.1.

Ruggiero, Peter, Paul D. Komar, and Jonathan C. Allan. “Increasing wave heights and extreme value projections: The wave climate of the US Pacific Northwest.” Coastal Engineering 57, no. 5 (2010): 539–552. http://dx.doi.org/10.1016/j.coastaleng.2009.12.005.

Ruggiero, Peter, M. G. Kratzmann, E. A. Himmelstoss, David Reid, John Allan, and George Kaminsky. National assessment of shoreline change—Historical shoreline change along the Pacific Northwest coast: U.S. Geological Survey Open-File Report 2012–1007. Reston, VA, US Geological Survey, 2012. http://dx.doi.org/10.3133/ofr20121007.

Ruggiero, Peter “Is the intensifying wave climate of the US Pacific Northwest increasing flooding and erosion risk faster than sea level rise?” Journal of Waterway, Port, Coastal, and Ocean Engineering (2013). doi:10.1061/(ASCE)WW.1943-5460.0000172.

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.doi:10.1002/2014JC010093.

 

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