Walking on Glass: Sustainable beaches

Old beer bottles, and coastal protection of the futur

By Holly McKelvey

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As you walk closer, the roar gets louder. A yawning metal pipe snaking out of the sea is blasting a liquid mixture of sand and salt water onto the beach. A caterpillar loader chugs along, redistributing the sand across the beach through a methodical choreography of forwards and backwards. About a kilometer offshore, a ship sits unobtrusively. This marks the other end of the pipe; below the ship, sand is being scoured from the sea floor, and piped to shore to build the beach anew.

This is the tranquil and touristic island of Sylt, off the northwestern coast of Germany. What is happening is called "beach nourishment" — sand lost through normal erosion is being actively replaced by sand from offshore, in order to protect Sylt's coastline.

Rebuilding beaches

But why replace an entire beach? Why not allow natural erosion to take its course, allowing the beach to slowly and naturally recede? The answer is largely an economic one, and simple: because people built houses and hotels and various other buildings along the beach at some point or another, and now they don't want it to fall into the ocean.

The slow and inevitable erosion of the western coast of Sylt means that the hotels, beautiful houses, summer retreats, and mini-golf courses that look out over the North Sea will begin to slump one by one into the water as the sandy cliffs erode away beneath them. Building out the beach below them slows the erosion of the cliffs by preventing waves from reaching them, thereby preserving the buildings that support Sylt's tourism-based economy. 

But the answer is longer than just the economics of it. Surrounding the issues of beach erosion and nourishment is the larger question of coastal defense: how best do we protect coastlines, particularly those inhabited by humans, from rising sea levels? And how do we do it best over the long-term?

This is a question that is becoming increasingly important as the reality of climate change makes itself apparent. Temperatures are projected to rise by a minimum of 2°C by the end of the century according to projections from the International Panel on Climate Change (IPCC), bringing with it projected sea level rises of anywhere from 50 cm to 1.5 meters. Island and coastal states around the world have already begun to see higher tides and stronger storms; flooding and erosion along coastlines is only going to get more extreme, meaning that coastal defense plans for coastal countries are an absolute must.

What does coastal defense look like?

The most familiar coastal defense systems are dykes, levees, and sea walls; these cement or stone barriers against the ocean are termed "hard" coastal defense, because they present an unyielding face to oncoming storm waves, and a reassuring sense of psychological security to those whose houses sit behind them. But these hard defense methods pose risks: the force of waves hitting the dykes can weaken them, and dyke failure can mean that inhabited areas lying behind them are instantly and often disastrously inundated. Think of the catastrophic flooding in New Orleans following Hurricane Katrina in 2005. These hard defense methods may provide a sense of strong security or protection, but when they fail, they fail hard.

So coastal managers have begun to turn to softer methods to cushion coastlines: rather than protecting coastal regions with stone or cement, they are creating natural barriers out of sand and soil to dull the force of waves. These can take several forms: most frequently dunes, constructed wetlands, or, as seen on Sylt, beach nourishment. Because of the lack of solid or permanent constructions between infrastructure and the ocean, such methods are described as "soft" coastal defense. Unlike hard coastal defense, soft methods do not aim to block waves completely. Rather, they create a buffer zone between the ocean and human infrastructure, where the oncoming waves of a storm can break and dissipate relatively harmlessly. As a wave flows up a beach, it loses its energy over the broad space, and by the time it reaches the bluffs above the beach, its erosive power is vastly reduced. 

Soft coastal defense techniques are increasingly preferred as both a cheaper, more sustainable, and more environmentally friendly solution for managing coastlines. High-tech engineering options such as levees and sea walls can be prohibitively expensive, as well as significantly altering the ecosystems around them. Replacing them when they are old, or when they begin to get undercut by wave erosion, is also an enormous undertaking. The construction of dunes or wetlands, meanwhile, can create or restore unique habitat for coastal species. And when the landscape shifts or is altered by storms, the solution is often as simple as depositing more sand.

Where does the sand come from?

On Sylt, sand is pumped up from offshore, and distributed evenly up and down the western-facing beach throughout the year. In the Netherlands, coastal managers use the ocean's force to do the heavy work: a mountainous spit of sand is deposited at one point along the beach, and left to be slowly redistributed up and down the coast by ocean currents.

The source of sand itself offers another option for sustainability, albeit an oddly unexpected one: some counties in the US have been using sand made from old, recycled bottles to nourish their beaches. Studies have shown that grains made from old glass are just as suitable for beach organisms as normal sand grains are, which means that the beaches of the future – and our coastal defense – might just consist of long stretches of tiny grains of glass, crunching under our feet as we go on our sunset strolls. So that next bottle of beer you drink? It might just be a step towards sustaining coast lines. Think of it as a service to future generations — Cheers!

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Holly is a graduate student in Environmental Management at the University of Kiel, Germany, where she cycles a lot, drinks tea, and enjoys the brief lapses of sunshine. She can be reached at mckelvey.holly@gmail.com

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