Audacious solutions for protecting against the next Hurricane Sandy

Three years ago, Superstorm Sandy ravaged seaside communities along the East Coast.

New York City's metropolitan area was severely impacted due to flooding damage done to its tunnels and subway system. Along the coast, storm surges were 14 feet above the average low tide. Sandy led to 48 deaths in New York alone, according to statistics from the National Hurricane Center.

The threat posed by increased flooding from future Sandys is very real due to the effects of climate change. New York could experience 6 more feet in sea level rise by 2100, which could potentially submerge more than 90 square miles of the city under water, according to a 2015 report published in the Annals of the New York Academy of Sciences. Major storms that once might have occurred every 500 years could soon happen every 25 years or so on the Atlantic coast.

In the face of rising sea levels and increased frequency of major storms, architects, scientists, and politicians are turning to creative protection solutions. Big waves call for big ideas.

"You can't just build on the risks we know about today, but also consider the risks that you can face over a lifetime and risks that extend farther out into the future," Joel Smith, an expert on climate change and a principal with Abt Associates, a consulting firm that aims to address social and environmental issues, told CBS News.

"It's about weighing the risk that you face, which you know about the likelihoods and outcomes, against the cost and feasibility of what you are trying to achieve."

Click through to see some of the most ambitious, promising projects for keeping future Sandys at bay.

The Big “U”

Following Hurricane Sandy, Henk Ovink, the former director general of water planning in the Netherlands, joined the Hurricane Sandy Rebuilding Task Force, which was part of the Department of Housing and Urban Development. Through the task force, Ovink started "Rebuild by Design," a 2013 competition that sought out the most innovative solutions for rebuilding and fortifying the New York and New Jersey coasts.

Six winning proposals were chosen out of 148 submissions and one of the most striking was The Big "U," an 8-mile-long flood wall at the edges of the East and Hudson rivers that would wrap around the southern tip of Manhattan.

The low, wide wall would consist of three contiguous sections that extend out from the coastline and up onto the land. Each segment contains a separate flood protection zone, while along the top of the wall, landscaped parks and promenades would complement the feel of each neighborhood it runs through.

For instance, an area of Lower Manhattan south of the Manhattan Bridge, where the highway that runs along the island's East River rises as an overpass above some of the city's lowest lying neighborhoods, deployable flood walls would be affixed to the underside of the roadway, flipping down at the onset of a storm.

Living flood barriers

Naturally occurring breakwaters, coral reefs, marshes and oyster beds can prevent or lessen flooding by mitigating powerful wave energy off the coast.

Living Breakwaters, another winning proposal out of "Rebuild by Design," would create a "reef street" along Staten Island's south shore. The proposal envisions a "necklace of breakwaters," miniature pockets of habitat for sea life like shellfish, lobsters, and fin fish that would buffer the shore against erosion, wave damage, and, of course, flooding.

The developers behind the idea view Living Breakwaters as a potential prototype that could be "replicable in other waterfront communities faced with the similar duality of risk and opportunity presented by their connection to the water," the project team wrote on the contest website. Beyond its flood-prevention potential, it would also go a long way toward conserving local marine ecology.

Maeslantkering

A storm surge barrier in the Netherlands, the Maeslantkering is one of the largest moving structures on Earth.

It comprises hydraulic sea gates that each weigh twice as much as the Eiffel Tower. Construction of the barrier, which extends across about a 394-yard stretch of water from the Rhine to Rotterdam, began in 1991, and didn't open until 1997.

The barrier is operated by a computer system that analyzes sea level and weather data. When a storm surge above about 9.8 feet above sea level is expected, the barrier closes on its own.

The gates are like giant floating pontoon boats that fill up with water. When the weather calms down, water is pumped out.

Giant tunnel plug

One of the most lasting effects of the superstorm was the damage done to underground tunnels for cars and subways. A subway tunnel connecting downtown Manhattan to Brooklyn was ravaged by about 27 million gallons of salt water that rushed through it. It took 13 months of repairs, costing $250 million, before it opened again to riders.

Back in January 2012, the Department of Homeland Security Science and Technology Directorate tested out a plug. Unlike the one you would use to stop water in your bathtub, this one is a hollow sack that can be deployed in a tunnel to trap water as it enters. Made of a thick webbing of Vectran, a liquid-crystal polymer fiber, it stores flat and can fill up in minutes to seal off a section of tunnel. The plug can inflate to about 32 feet long by 16 feet wide and can store up to 35,0000 gallons of water.

"No one's ever done this before," Science and Technology Directorate Project Manager John Fortune said in a press release. "It's completely novel technology."

The technology could be useful in cities with underground public transportation systems that run under large bodies of water. If there's a major flood, the plug could issue from a wall compartment stopping the water from rushing through the tunnel. The device is still being tested.

Multipurpose marina

Singapore's Marina Barrage opened in 2008 with much fanfare -- it was a costly project -- about $161 million in U.S. currency, adjusted for inflation -- that aimed to build a dam at the convergence of five separate rivers that would also become a major cultural attraction.

From above, its swirling design looks something like a green, grassy nautilus shell, curving inward. While its top surface is a city park, the barrage multi-tasks -- its main function is to keep the water at bay, protecting against flooding and the ever-encroaching threat of rising sea levels.

Another cool feature? When there's heavy rain during low tide, the reservoir's gates are lowered, releasing excess water back into the sea and. During high-tide, the gates stay open and drainage pumps churn excess water to the ocean.