Washington’s coastal areas and marine waters are not only a critical economic engine for the state but also provide an important sense of place and figure irreplaceably in the traditions and cultures of tribal communities. The state’s coastlines also provide valuable ecosystem services that support human and natural communities alike. Sea level rise will exacerbate existing risks and vulnerabilities, such as shoreline and coastal bluff erosion, storm surge, flooding and groundwater intrusion.

Washington State is due for a new sea level rise assessment. The science has advanced significantly since the last assessment by the National Research Council in 2012, in particular suggesting the potential for higher rates of sea level rise this century. In addition, previous assessments did not adequately account for differences in the rate of vertical land movement across the state, which affects how sea level rise is experienced on land. Finally, past studies have typically provided a low, middle, and high projection, with little guidance on how to interpret these in the context of sea level rise planning. We have developed a new set of projections that address each of these issues.

Our study begins with a new set of projections for absolute sea level rise (the height of the ocean surface relative to a fixed, unmoving reference point, such as the center of the earth). However, the impacts of sea level rise will be felt via a change in height of the ocean surface relative to land. To estimate relative sea level rise, we combine separate estimates of absolute sea level rise and vertical land movement (uplift or subsidence).

There are three distinguishing features of the new projections:

1. New Science. Our projections are primarily drawn from a recent comprehensive assessment of global and regional sea level rise. The new projections incorporate recent research indicating the potential for higher sea level rise in the 21st century.
2. Community-scale. Projections are developed for 171 locations distributed along Washington’s coastline. These account for variations in the rate of vertical land movement across the state.
3. Probabilistic. We assess the likelihood, for a given greenhouse gas scenario, that sea level rise will reach or exceed a certain level relative to the present. This probabilistic approach may be better suited for application to risk management and planning.

The authors thank Robert Kopp (Rutgers University), Robert Bindschadler (NASA), Li Erikson (USGS), Patrick Barnard (USGS), Lara Whitely Binder (King County) and Shaun O’Neil (King County) for their reviews and helpful contributions to this document.

KING 5: How changing sea levels could affect 171 Washington sites
Researchers hope the location-specific data about rising sea levels will help put disaster planning processes in action.

Seattle Times: Global warming may push Seattle sea level up 3 feet by 2100: report
The projections released Monday, based on the latest science, show what to expect at 171 sites in Puget Sound and along the coast. The idea is for local officials and planners to use them to weigh the risks.

KNKX: New coastal resilience report can help Washington prepare for sea level rise
As the climate warms, oceans expand and polar ice caps melt. This means sea level rise is a reality that land owners and local governments must prepare for. It brings with it associated risks, such as flooding and erosion which can impact everything from sewage treatment plants to roads and bridges.

The Sea Level Rise in Washington State – A 2018 Assessment report was a jointly-led effort by the Climate Impacts Group and Washington Sea Grant, in collaboration with the University of Oregon, University of Washington Earth and Space Sciences and the United States Geological Survey. This work is part of the Washington Coastal Resilience Project (WCRP), a three-year effort to rapidly increase the state’s capacity to prepare for coastal hazards, such as flooding and erosion, that are related to sea level rise. The overall aim of this collaborative project is to improve risk projections, provide better guidance for land use planners and strengthen capital investment programs for coastal restoration and infrastructure.