Coastal Environments: Current Research

Impacts of Climate Change on the Coasts of Washington State



Climate change on the Washington coast will trigger significant physical hazards: (a) inundation of low-lying areas by high tides as sea level rises (SLR); (b) flooding of coasts during major storm events; (c) accelerated erosion of coastal bluffs; (d) shifting of beach profiles, moving the Mean High Water line landward; (e) saltwater intrusion into coastal freshwater aquifers; and (f) increased ocean temperature and acidity. Various shore areas will respond differently depending upon substrate (sand versus bedrock), slope (shallow versus steep cliffs), and the surrounding conditions (exposed versus sheltered from storms).

One broad conclusion is that SLR impacts on coastal beaches and unstable bluffs will endanger housing and other structures (including ports and marinas) built near the shore or near the bluff edges. We characterize three responses to this threat as: (1) accommodation (e.g. build beach houses on stilts to alleviate the effect of higher tides), (2) protection (e.g. build seawalls to keep tides from reaching beach houses or from eroding the toe of bluffs), or (3) retreat (e.g. move threatened structures back from bluffs and beaches as sea level rises). State and local governments will need to do longer term planning to retreat from the threatened shores and bluffs, to invest in structural protection, or to accommodate to rising tides. We concluded that saltwater intrusion into coastal aquifers will be a relatively small threat, affecting some shallow aquifers used for water supply, for example, on Whidbey Island.

Shellfish may be harmed by increasing ocean temperatures and acidity, due to shifts in disease and growth patterns, and to more frequent HABs. Further, inter-tidal habitat for shellfish aquaculture will likely be slowly shifting shoreward as sea level rises. Adapting to these effects may involve both genetic research to select more resilient sub-species of shellfish and altered property boundaries to accommodate the shifting high tide lines.

Finally, the legal implications and difficulties associated with property boundaries tied to high tide lines was given specific attention, resulting in some suggestions for adaptation in the State property law. Further research will be a necessary element of any longer-term, adaptive strategy for climate change in the region.


Washington State Department of Ecology, Port of Seattle, Pacific Shellfish Institute, Western Washington University, Island County

Primary Funding

Washington State Legislature (House Bill 1303)

Related Publications

For publications on the CIG's research on climate and PNW coastal ecosystems, please see CIG Publications.

Huppert, D.D., A. Moore, and K. Dyson. (2009). Impacts of climate change on the coasts of Washington State. Chapter 8 in The Washington Climate Change Impacts Assessment: Evaluating Washington's Future in a Changing Climate, Climate Impacts Group, University of Washington, Seattle, Washington.