Within a generation, South Carolina’s coast could feature massive artificial reefs just offshore that would help slow down the biggest, most erosive waves headed toward its beaches.

These reefs would likely cost in the hundreds of millions of dollars, and if they're designed like others around the country, they would consist of broad-based mounds of rocks and sand just a few hundred feet offshore.

But would they actually work?

That's the question before South Carolina's first statewide flooding commission as it begins its task of finding the best ways to protect the state. Its members already have an abundance of big ideas to sort through — from these reefs to a third massive, man-made interior state lake. 

At the group's first meeting last month, the panel's members, split into 10 working task forces and all received binders full of ideas on how to deal with flooding that has inundated the state in recent years.

Chairman Tom Mullikin encouraged the experts to edit the proposals inside as they start their work this year, and participants who spoke with The Post and Courier said they saw the documents only as a starting point. 

Some of their initial ideas carry a hefty price tag and, in the case of an artificial reef designed to disperse waves, would be essentially unprecedented in the state. 

Others, like a new inland lake in Marion County, are modeled after existing feats of engineering: Lakes Marion and Moultrie, both of which are tourism destinations and hydroelectric power producing sites. Those bodies of water require constant management and complicated fixes to cater to wildlife like the Atlantic Sturgeon, however.

Like all big engineering projects, they have trade-offs—something the new flooding panel should look at closely when considering options, said Jason Crowley of the Coastal Conservation League. 

"That was a region of plantations and mostly African-American settlement communities that are now at the bottom of a very large lake," Crowley said of the created inland waterways.

An engineered reef

Among the most prominent of the proposals presented to the commission is to build an artificial reef along the state's coast to dissipate waves and storm surge. One of the panel's task forces is dedicated exclusively to studying that idea.

The proposed reef isn't like those that have already been placed offshore by the state's Department of Natural Resources. Those reefs are meant to attract marine life, making them popular spots for anglers and recreational divers.  

"Initially, they were accidental reefs in terms of sunken boats, and then people figured out this was a good idea to attract fish," said William Ambrose, a vice dean at Coastal Carolina University and a member of the artificial reef task force. 

But reefs designed to disperse wave energy — known more commonly among engineers as breakwaters — don't necessarily work the same way. In the United States, they've most commonly been used along the West Coast and near Hawaii.  

A breakwater is essentially a speed bump for a wave, making it break before it reaches the shore. DNR's reefs are too far out and too small to significantly impact the swell, said Tim Kana, of Coastal Science and Engineering. 

In order to act as intended, breakwaters have to be placed around 500 feet from the water line and reach close to or above the water's surface, at least within five feet, Kana said. And because they're parallel to the shore, they're far more complicated and expensive to engineer than some other more common structures meant to catch sand, like a groin, which is attached to dry land. 

"You can't just throw cement blocks out there; they'll get tossed around by the waves," he said. 

And even if a breakwater does help retain sand in one section of the beach, it may stop the natural flow to other areas, Kana added. 

'The hydrological threat'

Some of the other starting proposals are among the best practices suggested by researchers and flood mitigation experts, such as building up green infrastructure like living shorelines that keep the coast in place with plantings or oyster reefs. 

The "Landscape Beautification" task force, for example, will study how to best use green spaces and permeable surfaces in urban environments. A road map for local communities to lessen flooding through planning efforts is high on the wish list of environmental advocates across South Carolina. 

Still, other proposals land far afield of that objective. One floated in the commission's materials is desalinization, or removing salt from water to make it potable. The idea was presented in the white paper for the panel's economic development task force because severe floods can introduce pollutants into waterways, making it more difficult to purify drinking water drawn from rivers. 

But desalinization is an extremely expensive process, said Susan Libes of CCU. 

"The only communities that are doing this, they have absolutely no other options,” said Libes, a water chemist who is not on the flooding panel.

Drinking water quality isn't only a concern in times of flood. The state has seen several episodes of drought in the past decades, including one that was so severe in the early 2000s that saltwater starting intruding far up coastal rivers, threatening municipal water supplies. 

"You need to look at both sides of the hydrological threat," Libes said, "and it's funny that a decade or two ago we were all focused on the other threat."

Reach Chloe Johnson at 843-735-9985. Follow her on Twitter @_ChloeAJ.