Armed with a growing body of evidence that rising seas could inundate the California coastline sooner than later, state experts are sounding the alarm.
A new report, “Rising Seas in California: An Update on Sea-Level Rise Science,” stresses the potential for extreme sea-level rise because of uncertainties in projections of how ice sheets will melt due to their unique, hard-to-understand physics.
And it warns not to discount long-shot odds, such as a 1-in-200 chance of Southern California waters rising 2 feet above 2000 levels by 2050.
“Sea-level rise will continue to threaten coastal communities and infrastructure through more frequent flooding and inundation, as well as increased cliff, bluff, dune and beach erosion,” the report states.
“Not only are economic assets and households in flood zones increasingly exposed, but also people’s safety, lives, daily movement patterns and sense of community and security could be disrupted.”
Seven researchers with expertise in ocean and climate science wrote the report, which will be adopted by the state’s Ocean Protection Council next year after a series of public meetings. The study updates California sea-level rise research published in 2010 and 2013.
The work was done in collaboration with the National Research Council, National Resources Agency, Gov. Jerry Brown’s office, the state Ocean Science Trust and California Energy Commission.
Beach erosion, flooding
Coastal subsiding and extreme flooding have been – and will continue to be – exasperated by unusual events such as El Nino storms or a major earthquake.
Sand at Cabrillo Beach was nearly totally eroded last year by storm surges at San Pedro’s outer harbor, one of many similar scenarios reported up and down the state’s 1,100-mile coastline.
Rough seas routinely leave behind shorter beaches from Malibu to Long Beach, forcing lifeguards to move back their stations.
In Orange County, king tides have flooded the streets and low-lying homes near the beaches in Seal Beach, Sunset Beach and Huntington Beach, as well as Balboa Island and Balboa Peninsula in Newport Beach, in years past.
Recent weather systems have eaten away at the sand under the Newport Beach Pier. Nearby, this winter’s storm system left 8-foot walls of sand at Balboa Pier.
Just south of San Clemente at San Onofre State Beach, 100 parking spots were lost when part of the parking lot crumbled into the ocean. In November, San Clemente spent $600,000 to replenish the once-sandy North Beach, only to have a large storm eat half of the replacement sand in January, washing it into the ocean.
Such beach erosion and coastal flooding is cyclical but will become increasingly worse as sea levels rise, the report states. The result will be “sea-level-rise rates unprecedented at least in human experience,” the study states.
Sea-level scenarios
In a best-case scenario, research models show a likely ocean-level increase off La Jolla of about 6 inches by 2030 and one foot by 2050. A worst-case scenario predicts the ocean will rise more than 1 foot by 2030 and 2 feet by 2050, according to the study.
The report predicts the most extreme water-level increases will come after 2050, when ocean levels off Southern California could reach 2 to 10 feet above 2000 levels by 2100.
“This report offers an update on this understanding and provides the best available projections of future conditions,” the study says. “Our collective scientific understanding of sea-level rise is advancing at a very rapid pace. We encourage the creation of science-policy processes that are flexible, iterative and adaptive.”
Reducing emissions
The rate of increase will depend on the concentration of human-caused greenhouse gases in the air.
California is required to reduce its greenhouse gas emissions by 40 percent, to 1990 levels, by 2030. This is being accomplished with renewable energy, electric cars, required emissions caps, carbon offset taxes, and other methods.
Also, the uneven melting of Antarctica ice sheets will be a major contributor to rising seas in California.
“For every foot of global sea-level rise caused by the loss of ice on West Antarctica, sea-level will rise approximately 1.25 feet along the California coast,” the report states.
It goes on to warn that “uncertainty about the exact amount of future sea-level rise should not be a deterrent to taking action now.”
Lawrence Berkeley National Laboratory created maps outlining how the Antarctic ice sheet will retreat, as it melts. The project, dubbed BISICLES, illustrates several likely scenarios for how the floating ice shelves will waste away through 2200. It shows the most dramatic ice reduction occurring after 2100, with significant impacts to begin before that.
Planning for sea rise
Since beach erosion and coastal flooding take place routinely along California, local planners have already implemented fixes along the most vulnerable spots.
In the 1970s, Newport Beach installed a valve system on Balboa Island and the bay side of the peninsula to keep storm drains from backing up with too much water.
Aging seawalls wrap Balboa Island and Little Balboa Island to prevent ocean water from washing into roadways and homes. In Seal Beach, city workers routinely build sand walls each year to prevent flooding of beachside houses.
In Long Beach, the Aquarium of the Pacific prepared a “Climate Resiliency” report to help the city mitigate a variety of climate change and pollution impacts in 2015.
“Over the next few decades, the primary concern is with flooding from coastal storms,” that report states. “Over the longer term, the rise of sea level from climate change will compound the effects of flooding and inundation since storms will be superimposed upon a progressively higher stand of sea level.”
It uses the U.S. Geological Survey’s Coastal Storm Modeling System to predict local impacts.
“The western and eastern corners of southern Long Beach are at high risk of flooding during a 100-year storm (or a large storm surge) with no rise of sea level,” that study states. “Roughly 22,492 people are currently at risk of flooding.”
Sea-level rise will exasperate those high seas by flooding thousands more people during major storms, it states.
Studies to prepare for sea-level rise already have been done, and are continuing, at the ports of Long Beach and Los Angeles. Long Beach is considering modifications to its breakwater, while City Hall is logging its greenhouse gas emissions and researching ways to protect Alamitos Bay.
In San Pedro, Port of Los Angeles officials are drafting a study due in 2019 to find vulnerabilities and adaptations to reduce the impact of rising seas.
“The port is taking the potential for sea level rise into consideration as it designs and builds new developments,” spokesman Phillip Sanfield said. “For example, port engineers are designing the soon-to-be built Wilmington Waterfront Promenade with an additional 6 inches of height to account for sea-level rise. Private developers planning the San Pedro Public Market along the port’s main channel have raised the height of the planned building by a few feet in consideration of sea-level rise.”