A report by the United States Geological Survey Climate Impacts and Coastal Processes Team suggests that future sea level rise, in combination with major storms like the ones the state is experiencing now, could cause more damage than wildfires and earthquakes.
This is the first study that looks not just at sea level rise in California, but also sea level rise, along with a major storm to assess total risk to coastal communities.
“Even the storms today have significant risk to California’s coastline,” said Patrick Barnard, the lead author of the study. “There are about $12 billion in properties that are at risk of extreme storm today, but if you look out into the future, let’s say mid-century, those numbers roughly triple to about $30 billion of property at risk with just a little bit of sea level rise, and it goes up from there.”
The intent of the study is to educate communities that as storms pose a threat today, that threat will be amplified with the effects of sea level rise brought about by climate change. The report aims to give communities the ability to assess possible outcomes and, it is hoped, begin to take steps toward mitigation.
“Every new study reveals that the sea levels are rising faster and will go higher than previous projections,” said Jack Ainsworth, executive director for the California Coastal Commission, in an email. “We need to get serious about planning for and implementing resilience measures that will enable communities to adapt with the least amount of disruption.”
The Coastal Commission has provided nearly $7 million to coastal communities in the last five years to begin plans and resilience efforts. Some of the planning being discussed by some of the communities includes managed property retreat, building sea walls, and replenishing beaches.
The San Francisco Bay Area is entertaining the idea of building green levees that both provide flood protection and offer ecosystem value. The city of Encinitas, about 25 miles north of San Diego, has begun planning an incremental approach to mitigating the hazards of sea level rise. The plans include adding more riprap (loose stones used to armor shorelines) and putting sand on top of it, and also beach fill projects, which is replacing sand.
Beach fill is expensive, and the results don’t last forever. And some communities, like Encinitas, aren’t considering managed property retreat.
But the stakes are high, according to Barnard.
“When you look at just the annual, typical winter storm, combined with sea level rise expected by the end of the century, you’re looking on the order of about $50 billion of property at risk on sort of the medium end of the sea level rise projections,” he said.
The cost of wildfires during the years 2017 and 2018 was roughly $10 billion to $18 billion. The cost of a major coastal storm, combined with “medium” sea level rise would be five times that, Barnard said. “A higher level of sea level rise could raise that cost to $100 billion.
Again, this is the “do-nothing approach.” These projects consider infrastructure currently in place with little or no mitigation measures taken.
Although the models do indicate sea level rise, they don’t show an increase in storm intensity, although that could depend on El Nino events. “There’s a lot of uncertainty about El Nino frequency and the magnitude of the El Nino we’re going to see,” Barnard said. “Some studies suggest we’re going to have more extreme El Nino events, in which case we will see an increase in storm-induced hazards, but a little bit of sea level rise amplifies even the same storms we experience today.”
