Sea Level Rise: An Introduction

Sea level rise will cause:

  • Coastal flooding

  • Habitat loss

  • Salinity change in streams and groundwater

  • Erosion or deposition of material in waterways

Daily high tides will be higher and so will water levels during storms.

We can see what normal tides may look like in the future by viewing king tides and other extreme water levels today. 

There is no single number to accurately describe future sea level rise, but updated sea level rise projections were created for Washington State’s shorelines in 2018.

Sea level rise, town planning, and building construction are all slow processes, so begin acting now. 

Preparing for sea level rise:

  • Advocate for sea level rise language in local coastal planning efforts

  • Adapt your project to projected future water levels

  • Talk with your neighbors about higher future water levels

What is sea level rise?

Sea level rise is an increase in ocean water levels over long time periods (decades to centuries). Large increases in sea level expected by the end of the century are caused by:

  • Thermal expansion – when sea water warms, it expands.
  • Melting of land ice – when glaciers, ice caps and ice sheets melt, more water is added to the ocean, increasing its volume.

Both of these processes are due to global climate change. 

Local factors – such as tectonics and land subsidence – may cause variations in water levels, referred to as relative sea level rise. Relative sea level rise is the long-term (over multiple years or decades) average sea surface height relative to a fixed point on land. Relative sea level changes reflect both changes in absolute sea level (the average sea surface height relative to the center of the earth) and vertical movement of the land surface (i.e., subsidence or uplift). In Washington, vertical land movement can impact near- and long-term changes in observed and projected relative sea level rise.

North Cove, Washington.

How may sea level rise affect me?
The diagrams below show how sea level rise could impact your home, business or local shoreline.

If coastal flooding is a problem now, it will get worse as sea level rises. Sea level rise will cause daily tides to be higher. When storms occur during these high tides, water levels will reach higher on the shoreline. For places where coastal flooding is rare today, it will occur more often. Higher water levels on the coast can damage existing infrastructure, impact coastal ecosystems, and increase impacts from other coastal hazards.

How much will sea level rise, and when?

The most recent sea level rise projections for Washington State were produced in 2018. These projections describe future sea levels for more than 150 locations across Washington State’s coastline. They incorporate the latest science, account for our region’s active tectonics, and assign probabilities to different magnitudes of sea level rise. The table below shows a summary of this information for seven locations in Washington. 

Sea level rise will impact each place differently due to factors such as vertical movement of the land surface (i.e., subsidence or uplift). To see how sea level rise may impact your location, visit NOAA’s Sea Level Rise Viewer. Using the numbers from the chart above (or the 2018 Washington Sea Level Rise Projections), move the viewer’s slider to show future water levels on the map. For more detailed instructions, see the sea level rise visualizations and “How can I see these projections on a map?” on the Sea Level Rise: Research and Tools page. Here you can also learn more about how extreme events relate to sea level rise.

NOAA’s Sea Level Rise Viewer, showing average high tides in South Bend and Raymond, WA with 3 feet of sea level rise.

Why should I care now?
Sea level rise projections show future water levels, but we need to act now to ensure that tomorrow’s shorelines and communities are resilient. Planning for sea level rise now can keep your community safe from hazards now and in the future. Adjusting the design of your project to accommodate higher waters can save money later, and can also preserve coastal habitat functions that assist social and ecological resilience to sea level rise. 

Our highest annual tides are called king tides. They occur when one or more astronomical events happen at the same time. While King Tides are not caused by sea level rise, they do give us a glimpse of the future: today’s king tides are comparable to normal water levels in the future. For more information, see Washington Sea Grant’s King Tides Program (source: King 5).

What can I do about it?

Educate yourself:

 

Get involved in local coastal planning:

  • Contact local planners, planning commissions or Marine Resource Committees to share experiences, voice concerns, recommend that public projects account for sea level rise or attend a public meeting.
  • Engage with local Shoreline Master Program or Comprehensive Plan (Growth Management Act) updates to encourage wise planning for the future.
  • Download the MyCoast app to document storm surge, king tides, changes to your local shoreline, and more. This information is used to better understand coastal hazards and their impacts, while raising awareness among decision-makers and stakeholders.

 

Adapt your project to sea level rise:

Strategically-placed woody debris protects the drainage canal and Highway 105 in North Cove, WA from high waters (source: Molly Bogeberg, The Nature Conservancy).

Where can I learn more about sea level rise in Washington?

See our Sea Level Rise: Research and Tools page for the 2018 Sea Level Rise Projections for Washington State, an interactive map to find local sea level rise projections, and other resources.

See our Coastal Hazards Risk Reduction Project Mapper for case studies of projects adapting to sea level rise and other coastal hazards.

See our Planning Assistance page for resources related to jurisdictional planning for sea level rise.

See our Glossary of Sea Level Rise Terms.

Related hazards introductions:

Download this introduction as a PDF: Sea Level Rise Introduction.