In a state where rising sea levels are threatening oceanfront property, building $20 billion worth of seawalls would protect South Carolina’s coast from the effects of climate change during the next 20 years, a new study says.
The report by the Center for Climate Integrity says South Carolina needs 3,202 miles of seawalls — enough to cover the entire coast — to shield its beaches, marshes and tidal rivers from sea-level rise. The $20 billion cost estimate was based on a six-inch rise in sea level and a 21-inch storm surge, climate center officials said.
Nationally, the United States needs more than 50,000 miles of new seawalls, which would cost $416 billion, to protect the coastline from sea level rise, according to the climate organization, which supports aggressive efforts to halt climate change.
Building thousands of miles of sea walls is unlikely to happen, but the study was done to show the costs coastal communities face from climate change and moderate sea level rise by 2040.
The Center for Climate Integrity is a national advocacy group that wants big oil and gas companies to pay compensation to communities hurt by global warming. Many of these companies contributed to the increase in greenhouse gases that are trapping heat and causing the climate to warm up, the group says.
The report, written in collaboration with researchers at the University of Colorado and an engineering firm that specializes in climate issues, is believed to be the first to measure the cost of erecting new seawalls nationally in the next two decades as a way to combat sea level rise.
Six of nine counties in South Carolina face more than $1 billion in costs to protect themselves from sea-level rise in the next 20 years, the study said. Those counties include Beaufort, Charleston and Georgetown. Horry County, home to Myrtle Beach, faces just under $1 billion in costs, the study’s authors said. The study focused on areas that had public infrastructure, such as roads and bridges.
Seawalls needed to fortify the coast include those that protect property along the beachfront, as well as walls to protect properties on tidal creeks and coastal rivers, according to the Center for Climate Integrity. Seawalls are often effective at protecting homes, roads, hotels and other property, but when established on eroding beaches, they block public access and make shoreline erosion worse. They also can worsen the erosion of salt marshes.
The climate group’s study was released as policy makers in South Carolina consider whether to lift the state’s 30-year-old ban on new oceanfront seawalls. Seaside property owners are increasingly asking for exemptions to the state’s seawall ban to protect their investments. This past year, the Legislature approved an exemption to the seawall ban for one community, but Gov. Henry McMaster vetoed the proposal.
The report’s authors acknowledge that seawalls and bulkheads may not be the answer for every community threatened by sea level rise. Many probably won’t be able to afford the cost, they said.
But they said the report shows that rising sea levels are a real threat that will require property owners to soon take action to avoid being flooded out. In some cases, people may want to move away from the oceanfront, the study said.
“Some regions will be able to reduce their protective costs in exchange for relinquishing some land to the sea,’’ the study said. “In areas where the costs to protect their communities are greater than the cost to relocate, community members may be forced to consider managed retreat.’’
The study said hundreds of small coastal communities will have to abandon threatened areas unless “enormous amounts of financing emerge in a very short period of time.’’ But even then, the cost to relocate could be expensive because property owners would have to be compensated, the report said.
In South Carolina, the policy of “retreat’’ was written into state coastal law for decades until South Carolina legislators recently removed it. The report says such a retreat “is controversial due to the social and psychological difficulties associated with removing people from their homes.’’
John Tynan, director of the Conservation Voters of South Carolina, and coastal geologist Rob Young said building a huge network of seawalls would be a bad idea. Seawalls won’t stop many types of flooding, but they will take a toll on the beaches and marshes across the Carolinas and the nation, said Young, who runs a program that studies erosion and shoreline change at Western Carolina University.
“If we did that, there would be no marshes or beaches left anywhere,’’ Young said. “If you build a seawall in a place where the water is rising, then that beach or the marsh is going to disappear in front of that seawalls.
“It’s a ridiculous premise. Nobody really wants to do this. In the state of South Carolina, we recognized three decades ago that building seawalls has problems, and that’s why you can’t do it on the oceanfront. I’m assuming they are doing this to make a point of how much it would cost if you tried to do it.’’
The climate center report was released in the same week that President Donald Trump’s administration dropped an effort begun under former President Barack Obama to set national limits on carbon dioxide released by power plants. The new Trump rule leaves the amount of reductions up to states. Coal-fired power plants are major generators of carbon dioxide, a greenhouse gas.
The New York Times contributed to this report.