About the King Tides Project

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What are King Tides?

While the term "King Tide" isn't a scientific term, it is used to describe very high tides, caused when there is alignment of the gravitational pull between sun, moon, and Earth. When King Tides occur during floods or storms, water levels can rise higher and have the potential to cause great damage to the coastline and coastal property.

King Tides:

  • occur naturally and regularly,
  • are predictable and expected, and
  • are not an everyday occurrence.

Watch a video from the Exploratorium explaining King Tides.

Climate change, sea level rise, and king tides

The sea level rise we're experiencing now and will experience in the future is caused by the growing concentration of carbon dioxide (CO2) in the atmosphere created when people burn fossil fuels like coal, oil, and gas. Carbon dioxide in our atmosphere acts like a blanket, trapping in heat that would otherwise escape, and when we burn fossil fuels, we're adding more carbon dioxide, "thickening the blanket" and warming the planet and ocean. Sea level is rising because land-based glaciers and ice sheets are melting into the ocean and also because water expands in volume when it warms. Increases in global sea levels have been recorded by tide gauges since the late 1800s, and more recent observations have been collected by NASA satellites. The amount of sea level rise we will ultimately experience will depend on how quickly we stop burning fossil fuels.

California will be greatly impacted by sea level rise. For example, San Francisco is projected to see a rise between 1.1 and 2.7 feet by 2050, and by 2100 could experience between 3.4 and 6.9 feet of sea level rise with a potential for more than 10 feet of rise if there is extreme melting of the West Antarctic ice sheet (State of California Sea-Level Rise Guidance, 2018 Update). Learn more about sea level rise.

King Tides themselves are not related to climate change, but they allow us to experience what higher sea level will be like. King Tides are the highest high tides of the year—one to two feet higher than average high tides, which is a good approximation of how high we expect everyday tides to be over the next few decades due to human-caused sea level rise. When you observe the King Tides, imagine seeing these tides (and the associated flooded streets, beaches, and wetlands) every day. Understanding what a King Tide looks like today will help us plan for future sea level rise. Sharing your photos and talking about what you've noticed helps others understand that they're part of a community that cares about the climate crisis and wants to take action.

How are King Tides photos used?

King Tides photos help:

  • document current flood risk in coastal areas,
  • visualize the impacts of future sea level rise in a community,
  • ground-truth and validate climate change models by comparing model predictions with the high-tide reality,
  • serve as a living record of change for future generations.

Photos may be used in presentations, exhibitions, websites and publications on sea level rise impacts, coastal initiatives, and climate action. Photos may also be used by government agencies for research and planning to assess where the coastline is most vulnerable, and by scientists to better predict future sea level rise. Teachers and students use these photos to learn about our coastal geography and the impacts of climate change.

Who is the California King Tides Project?

The California King Tides Project was launched in the winter of 2010/2011 by a partnership of state and federal agencies and non-profit organizations. The California project is now part of a global network of King Tides initiatives along both coasts of the US, Canada, Australia, New Zealand, Europe, and Asia. In California, partners include the California Coastal Commission, San Francisco Bay Conservation and Development Commission, California State Parks, San Francisco Estuary Partnership, Coravai LLC, California Coastkeeper Alliance, USC SeaGrant, California Department of Fish and Wildlife, Tijuana River National Estuarine Research Reserve, San Francisco Bay National Estuarine Research Reserve, Nature Collective, Tolowa Dee-ni' Nation, California State Parks, Friends of Five Creeks, Friends of Sausal Creek, Friends of Arcata Marsh, Friends of Rose Creek, Friends of Famosa Slough, Save The Bay, The Ocean Institute, Surfrider Foundation, Baylands Nature Interpretive Center, Big Break Regional Shoreline, Humboldt Baykeeper, San Mateo County Harbor District, San Mateo County, Elkhorn Slough National Estuarine Research Reserve, The Exploratorium, Port of San Francisco, Pacific Grove Museum of Natural History, City of Oceanside, City of Pismo Beach, City of Ventura, City of Arcata, Greenspace-The Cambria Land Trust, Green Foothills, Preserve Calavera, Golden Gate Audubon, Navarro-by-the-Sea Center, Sonoma Coast Surfrider, ECOSLO, Sanchez Art Center, Grassroots Ecology, Climate Action Santa Monica, San Diego Natural History Museum, Silicon Valley Bicycle Coalition, Sierra Club San Francisco Bay, Latino Outdoors North Coast, UC Scripps Coastal Reserve.

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