Pacific Institute

The impacts of sea-level rise on the California coast

Over the past century, sea level has risen nearly eight inches along the California coast, and general circulation model scenarios suggest very substantial increases in sea level as a significant impact of climate change over the coming century. This study includes a detailed analysis of the current population, infrastructure, and property at risk from projected sealevel rise if no actions are taken to protect the coast. The sealevel rise scenario was developed by the State of California from medium to high greenhouse gas emissions scenarios from the Intergovernmental Panel on Climate Change (IPCC) but does not reflect the worstcase sealevel rise that could occur. We also evaluate the cost of building structural measures to reduce that risk. If development continues in the areas at risk, all of these estimates will rise. No matter what policies are implemented in the future, sealevel rise will inevitably change the character of the California coast.

We estimate that a 1.4 meter sealevel rise will put 480,000 people at risk of a 100year flood event, given today’s population. Among those affected are large numbers of lowincome people and communities of color, which are especially vulnerable. A wide range of critical infrastructure, such as roads, hospitals, schools, emergency facilities, wastewater treatment plants, power plants, and more will also be at increased risk of inundation, as are vast areas of wetlands and other natural ecosystems. In addition, the cost of replacing property at risk of coastal flooding under this sealevel rise scenario is estimated to be nearly $100 billion (in year 2000 dollars). A number of structural and nonstructural policies and actions could be implemented to reduce these risks. For example, we estimate that protecting some vulnerable areas from flooding by building seawalls and levees will cost at least $14 billion (in year 2000 dollars), with added maintenance costs of another $1.4 billion per year. Continued development in vulnerable areas will put additional areas at risk and raise protection costs.

Large sections of the Pacific coast are not vulnerable to flooding, but are highly susceptible to erosion. We estimate that a 1.4 meter sealevel rise will accelerate erosion, resulting in a loss of 41 square miles (over 26,000 acres) of California’s coast by 2100. A total of 14,000 people currently live in the area at risk of future erosion. Additionally, significant transportationrelated infrastructure and property are vulnerable to erosion. Statewide flood risk exceeds erosion risk, but in some counties and localities, coastal erosion poses a greater risk. This report also provides a comprehensive set of recommendations and strategies for adapting to sealevel rise.

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