Under High Water
Washington Sea Grant helps citizens and coastal planners understand what sea-level rise means for their communities
Visit Seattle’s Golden Gardens park on a sunny summer day, and you’re likely to find a crowd of happy-go-lucky locals playing on the beach and enjoying the spectacular views of Puget Sound and the Olympic Mountains beyond. Thanks to climate change, such idyllic days are under threat. As the Earth continues to warm, the ice sheets will continue to melt and the water that makes up the ocean will continue to expand—and the seas will continue to rise. Which means that Golden Gardens, along with many other culturally and economically important areas in Washington, could one day be under water.
As part of the Washington Coastal Resilience Project (WCRP)—a three-year effort funded by the National Oceanic and Atmospheric Administration in 2016—Washington Sea Grant and the University of Washington’s Climate Impacts Group led an effort to provide the most detailed picture yet of what sea-level rise could mean for Washington State. Released last summer, the report includes projections for 171 coastal sites from now through 2050. The report provides estimates of the possible ranges of future water levels for each site, with the goal of helping planners and decision makers weigh the risks of sea-level rise under different climate scenarios.
If we manage to limit future greenhouse gas emissions, the report’s best estimate for sea-level rise by 2100 is about 1.5 feet. However, due to uncertainty about the various processes that contribute to sea-level change, even under this optimistic emissions scenario seas could rise by more than seven feet. These projections threaten much more than Washingtonian’s leisure time at the beach: the state has more than 3,000 miles of coastline, and more than 400 square miles of land at an elevation within three feet of the high tide line. These areas are already susceptible to flooding and wave damage from winter storms, and will only become more so as the high-tide line rises. Important infrastructure and about 9,000 homes worth more than $5.25 billion in total have been built in these vulnerable areas.
However, not all of these areas will be impacted equally. Understanding these site-to-site differences is the first step in enabling communities to adapt to their changing shorelines. At the same time the sea is changing elevation, so is the land—but the nature of this land movement varies. In some areas, such as Neah Bay, the local geology results in the land rising, while in other areas, such as south Puget Sound, the land is sinking. These variations in land motion influence how sea-level change affects a community—a community on land that is uplifting will experience slower rates of sea-level rise than a community on land that is subsiding.
Incorporating land movement—and being able to say how much sea-level rise will be felt at a specific location—makes the report’s findings especially useful to coastal planners. The localized projections are publicly available on the WCRP website and can be easily accessed using an embedded Google map through which anyone can download estimates for a particular location.
“One of the things we’ve heard from the planners we have shown it to so far is ‘Hey, for the first time we have something that we feel is actionable,’” says Ian Miller, a coastal hazards specialist at Washington Sea Grant and lead author on the report. “I hope we’re going to hear that more, and that these projections will find their way into planning processes at the community scale.”
The projections could help communities make decisions such as prioritizing the infrastructure that could find itself under high water. “There are two factors that determine what steps a community might take to adapt, and both really need to be decided at the local level,” explains co-author Guillaume Mauger, a research scientist at the Climate Impacts Group. “First, what is the context: is it a hospital or other piece of critical infrastructure or is it a park? That’s your risk tolerance. And second, what is your value judgment of the amount of risk that’s acceptable?”
WCRP is working with pilot communities to help local governments meet these local needs. For example, MetroParks Tacoma used the projections to help design a waterfront park, including where to position important infrastructure that could be vulnerable to flooding. The Washington Department of Transportation has already used the projections, for example, to help design portions of State Route 167.
Preparing for sea-level rise will undoubtedly continue to be a difficult process—but the more information that can be used to help guide these decisions, the better. Washington Sea Grant has remained a leader in this conversation: for example, Nicole Faghin, coastal management specialist, held workshops in November and February to help coastal planners understand the projections detailed in the report. The workshops were filled to capacity, attended by coastal planners, resource managers, public works staff, parks department staff, tribal representatives, conservation district staff, and private consultants working with all of these agencies’ staff on projects and plans related to our shorelines.
“People want to learn about the latest science and how to apply it in their daily work,” Faghin says. In spite of the many challenges ahead, the response from local communities gives us hope that we will make progress toward addressing them.