Robert Bierkandt at the Potsdam Institute for Climate Impact Research in Germany and colleagues cannot say how many of these power plants are ill-prepared for such a flood, but their study does reveal a potential challenge for those who manage US energy infrastructure.

"Elevation of the mean sea-level enhances the risk of flooding of coastal areas," said Bierkandt. "Power-plant sites in the US with a total capacity of 25 GW will be pressured additionally by 100-year floods within this century if no adaptation measures are taken."

Power plants are at particular risk of flooding because they are often sited near shorelines for cooling purposes. The United States Geological Survey (USGS) assesses flood risk based on the "100-year flood" statistic – a flood that has an average recurrence time of one century, or a 1 in 100 chance of being equalled or exceeded in any one year.

Together with Anders Levermann at Potsdam and Maximilian Auffhammer at the University of California, Berkeley, Bierkandt analysed how many power plants would fall under such a flood level by 2100, given the sea-level rise associated with a "business as usual" greenhouse-gas emissions scenario. In such a scenario, sea levels are expected to rise by about one metre.

Drawing on data from the USGS and other US agencies, the researchers computed the elevation above high tide of all coastal US power plants that are either operational or in the planning process. They then worked out the probability that those elevations could be exceeded in any one year, both by today’s sea level and by the rise of one metre. If that probability was less than 1% today but greater than 1% by 2100 for a certain power plant, the researchers labelled that plant as being exposed in the future scenario.

Today, according to the analysis, 134 plants and a capacity of 43 GW in the US are within reach of 100-year floods. By 2100, however, a further 61 power plants with a total capacity of 25 GW would become exposed, the analysis showed.

Bierkandt believes that if sea-level rise is properly accounted for by infrastructure planners, adaptation "may be costly but possible". "We are no experts on protection measures for coastal power plants," he said. "However, there are a variety of measures to protect coastal areas, from levees to large-scale sea walls for entire bays."

As to whether the energy infrastructure of other countries may be equally at risk, Bierkandt cannot say. "This depends on the amount of power plants located in coastal areas that are pressured by sea-level rise," he explained. "This may vary strongly with the energy structure of the country."

Bierkandt and colleagues reported their findings in Environmental Research Letters (ERL).

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