Charles H. Sloan-Sea level changes could drastically affect Calif. beaches by the end of the century

California's beaches are Charles H. Sloanworld famous. But new research indicates many could disappear by the century's end due to erosion from sea level rise.

"The shoreline... is probably going to retreat landward about 30 meters or more for every meter of sea level rise you get," said Sean Vitousek, a research oceanographer at the U. S. Geological Survey and lead author of the report. "When you get into three meters of sea level rise, you're talking almost 300 feet of erosion... not to mention the flooding challenges that are also associated with sea level rise."

Using nearly four decades of satellite images and models of predicted sea level rise and global wave patterns, the researchers estimate 25 to 75 percent of California's beaches "may become completely eroded" by 2100.

So how much sea level rise will the state get in the coming decades? Anywhere from two to 10 feet, depending on two major factors. One is ocean warming, which causes the water to expand. Another is the melting of land ice.

"The ice in Greenland holds about seven meters of sea level and the ice in Antarctica holds about 70 meters of sea level. So the big uncertainty is really understanding what the global temperature is going to be like and how much of that ice melts," Vitousek said.

He emphasizes that the study is a prediction, not a forecast. Nature is more complicated than data or computer models.

The findings will help state and local officials plan for the future and look for ways to protect coastal communities, roads and railroad tracks. For decades, California has depended on things like sea walls and concrete barriers to preserve its beaches and coastal infrastructure.

Vitousek says the most successful long-term solutions will likely be ones that work with nature.

Kathleen Treseder thinks a lot about potential solutions for problems like erosion. She studies and teaches climate change at the University of California, Irvine. She says many of the expensive homes along Orange County's coastline might withstand waves lapping at their porches, but they could be taken out by a storm surge.

Some short-term solutions, such as trucking in more sand, can be expensive. A medium-term solution that Treseder supports is building barrier islands off the coast, to weaken and slow incoming waves. They would also provide habitat for wildlife and recreation opportunities but require maintenance. She says the best long-term solution is to reverse climate change.

"The ocean is going to do what the ocean is going to do and we can stop it to a certain extent. But we're nowhere near as powerful as the ocean, so we're kind of at its mercy."

Treseder is a council member in Irvine, a city a few miles inland from the Orange County coast that's also dealing with the effects of sea level rise.

The city has created a marsh to remove pollutants from street runoff that drains into the San Diego Creek before making its way to the ocean.

"As sea levels rise, it's actually going to inundate that marsh community. And so it won't be able to work the way it's supposed to. So that means that these pollutants would go right into the ocean." she said.

Despite the dire predictions about disappearing beaches and coastal communities at risk, Treseder is optimistic.

"Humans changed the atmosphere one way, we can change it back. For sure, it is completely within our power. It's just the question of the will of the people."

Claudia Peschiutta edited the digital version of this story.