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Natural Environment

The coastal erosion conundrum

Development on the shoreline pits the irresistible force of the sea against the immovable object of steel and concrete – and it's a fight neither side is winning.

John Vidal, Author and former environment editor of the Guardian
4 September 2019

Dawlish Warren beach in Devon is one of the most popular in Britain. Thousands of holidaymakers head there each year to enjoy its golden sands and pristine waters. But although the shoreline looks natural, it is, in fact, artificial. Since mid-Victorian times, when Isambard Kingdom Brunel engineered a railway line along this stormy, wave-lashed stretch of coast, people have tried to "defend" Dawlish and its beach from the sea with ever more elaborate projects.

The original sea wall of 1843 has been heightened and strengthened at least four times, and wooden groynes, breakwaters, stone revetments, concrete and steel gabions and rock "armour" have all been deployed to stop the beach eroding, the cliff crumbling and houses flooding.

By the early 2000s, Dawlish's famous sands were disappearing, leaving rock pools and shingle in places. The foreshore was much lower and narrower than it had been, and waves were frequently topping the sea wall during strong winds and high tides. Disaster struck on 4 February 2014, when storms dramatically collapsed the railway line that runs atop the wall, battering the defences and forcing evacuations. The government put up £35m for repairs to the track, and £14m for stronger beach defences.
Higher, stronger concrete walls, longer timber groynes and breakwaters and a new 460m sandbag defence were constructed. In addition, 250,000 m3 of sand was dredged from the nearby Exe estuary and pumped on to the beach, raising it 3m in places.

After spending £35m repairing the track at Dawlish in Devon, which was washed away in February 2014, the UK government committed £15m to developing a long-term resilience plan for the vulnerable infrastructure

But five years on, the problem is far from being solved. Storms again washed away much of the sand last year, and new plans to raise the sea wall a further 2.5m to 7m were submitted in February this year.

"It's still a beautiful beach, though. It's possible much of the sand will return over time", says an optimistic Suzanne Papanicola, spokeswoman for the Hazelwood Holiday Park, which lies just behind the beach.

As sea levels rise, storms get stronger and the world's coasts become lined with development, cash-strapped governments and communities from Spain to Brazil and Australia to California are grappling with what to do with their crumbling sea defences.

The old assumption that stronger, higher walls can hold back the waves is being challenged by marine geologists who argue that building "hard" defences and removing natural barriers such as sand dunes and mangroves leads only to the disappearance of beaches, worse flooding and an endless cycle of expensive repair and reconstruction.

"The sea wall itself is the problem", says Andrew Cooper, professor of coastal studies at the University of Ulster. "It cannot absorb the energy of the sea. Sea walls cause beaches to steepen, which means that bigger waves with more energy reach the remaining beach, scouring out the sand and undermining the defences. The more that we build sea walls, the more we destroy our beaches

"If you build a sea wall to protect the shore, the inevitable consequence over time is that the beach will [eventually] disappear. When you build the sea wall, that is the effective end of the beach", he adds.

"Sea walls are the deadly enemies of beaches. We are obsessed with building and defending property right next to the beach and trying to hold the beach in place", says Orrin Pilkey, author, with Cooper, of The Last Beach and professor of earth and ocean science at Duke University in the US.

Pilkey, now in his 80s, has long advocated natural beaches where possible but says that the future of the world's coastlines is uncertain because the coast is inherently dynamic and changing. He despairs of the situation in the US, where beachfront developments mushroom and engineers lock cities into expensive projects to continually strengthen their defences. The only solution, he says, is to move development back from beaches altogether: "In its efforts to hold the shoreline still, today's society is engaged in a costly and ultimately futile battle. On the one side is the coastal engineering fraternity and on the other the inexorable forces of nature. Many beaches on developed coasts have been transformed into long, thin engineering projects. These strips of sand that we call beaches were once a precious natural environment that has been destroyed in a misguided view of the good of humanity."

Beach wear

The price paid for trying to hold the sea back with steel and concrete is seen all along American, European, Australian and increasingly, Asian coastlines. In Japan, where nearly 40% of the coast is now lined with massive concrete walls to guard against tsunamis, beaches are disappearing at an alarming rate. The government's Institute for Environmental Studies forecasts that a combination of rising sea levels and seawall construction threatens to completely wash away 60% of Japan's sandy beaches.
Some of the worst coastal erosion in Asia is taking place in Vietnam, where developers have rushed to build coastal holiday resorts. The result, in places such as Unesco World Heritage Site Hoi An, and cities like Da Nang, has been beaches disappearing and defences crumbling, and projected revenue losses to the tourism industry of nearly $30m.

In the US, where the government estimates there are around 350,000 structures located within 150m of the sea, nearly 14,000 miles (22,500km) – 14% of the entire coastline – has been fortified with concrete, according to a 2015 report from the Marine Science Center at Northeastern University. What were wide stretches of sand just 30-40 years ago are often now narrow strips of beach sited below high walls. Meanwhile, research published in June 2018 by the Florida Department of Environmental Protection found that almost half of the state's 820 miles (1,320km) of coastline are now "critically eroded". Most of the state's coastline is "defended" behind sea walls, which are partly responsible for the beaches' disappearance.

The worldwide response to eroding beaches has been to replenish them with dredged sand. This temporarily widens them and maintains beachfront property values, but is expensive and must be done frequently. Beach "replenishment" is now a booming global industry, with one academic study suggesting $100bn a year is spent restoring US beaches alone. Hundreds of US barrier islands off the coasts of North Carolina, New Jersey, Texas and Florida now need massive, regular supplies of sand. On Galveston Island in Texas, the beach has been raised up to 5m, and the ground floors of some buildings have been turned into basements.

Many cities now replenish their beaches every year to keep the tourist industry alive. California is estimated to have pumped 300m m3 of sand on to its beaches over the past 30 years, and Florida 230m m3. But as storms increase and demand for sand grows, the cost of replenishment is spiralling. The wealthy residents of Malibu's Broad Beach in California received approval last June to add 300m m3 of sand to their short length of coastline at five-year intervals for the next 20 years. It is expected to cost them $31m.
They might be wasting their time. Geologists warn that sand replenishment actually worsens the erosion. "These artificial beaches usually erode at least twice as fast as natural beaches and can only ever be a temporary solution. As time goes on and as the sea level rises, the interval of replenishment will get shorter because the beach becomes less stable," says Cooper. "Beach replenishment is only a plaster that must be applied again and again at great cost. It doesn't remove the problem, it treats the symptoms. Eventually and inevitably beach replenishment will stop, either as sand or money runs out."

Replenishment also smothers all life on the beach, adds Pilkey. "The near-shore food chain that originates with the tiny organisms living between grains of sands and surviving on occasional influxes of seaweed is now gone. The whole ecosystem is out of whack. Habitats for turtle and bird nesting are being destroyed."

The powerful American Shore and Beach Preservation Association (ASBPA), the leading advocate of beach replenishment, condemns both sea walls and letting nature take its course. "Centuries of coastal development and engineering coastlines and inlets have caused much of the coastal erosion we see today. Sea-level rise will only make this worse. There is no way to now let nature take its course without reversing the events of the past 300 years," says Asbpa director Derek Brockbank. "Replenishing the sand that is lost is a critical tool to maintaining healthy coastlines. It costs money, but it is preferable to the cheaper – but ecologically destructive – alternative of building sea walls to protect coastal property."

British beaches are some of the most heavily eroded in the world. Government subsidies to maintain hundreds of miles of sea walls, groynes, artificial beaches and breakwaters cost more than £750m a year. But this has not stopped flooding, or beaches in places like Ventnor on the Isle of Wight, Lowestoft in Suffolk and Aberystwyth in Wales being eroded. The Welsh Environment Agency calculates that there are 220,000 properties, housing 357,000 people, at risk of flooding in Wales. Just to maintain this level of risk would require spending on defences to be tripled in the next 15 years.

Will Trust in nature pay off?

The National Trust, Britain's greatest coastal landowner by far with more than 780 miles of mostly wild shoreline, is one of the world's leading advocates of letting nature take its course.

"Hard coastal defences such as concrete walls have major drawbacks and a limited lifespan. They will be increasingly prone to failure," says Phil Dyke, the Trust's coastal and marine adviser.

"As they fail we need to make decisions about whether or not to replace them. We must also acknowledge that sea defences often cause unwelcome side effects, such as beach lowering in front of sea walls."

The Trust has more than 80 coastal sites experiencing rapid erosion, many with historic structures that are likely to be lost to the sea in the next 50-100 years. The answer, it says, is not to try to protect them behind high sea walls but, wherever possible, to let the sea create new wetlands, salt marshes and habitats. It also proposes moving buildings such as cafes, beach huts and even homes back from the coast.

"For many years, the default response to flooding and erosion along the coast has been to 'hold the line' and build our way out of trouble. The assumption was always that we could engineer solutions. [But] this endless cycle of 'construct-fail-reconstruct' makes little sense," Dyke argues.

"Increasingly we must view adaptation as having an equal role in the long-term health of the coastline. We are not against coastal defences, but they are not appropriate to us. They are very important for towns and cities but the way they are funded [by government] is that every £1 spent on sea defences has to demonstrate it can protect £8 of assets. This means there will be a lot of small coastal communities where the numbers don't add up", says Dyke.

"There is far better understanding of coastal processes compared with 30 years ago, but the public still expects that sea defences should be hard engineered.

"Progress is still equated with hard defences. It is quite understandable", he says. But, Dyke adds, coastlines were never intended to be static, and new thinking is needed.

Among the proposals for Dawlish is a new sea wall, 2.5m higher than the present one, plans for which were submitted in February. It remains to be seen how long term a solution this is, both for the beach and the railway.

That's ecological

Increasingly, an ecological mindset is being adopted. "The traditional approach of engineered sea defences locks us into ever increasing costs of replacement and maintenance. The alternatives are nature-based solutions to flooding and erosion, which work with natural processes to reduce flood risk and incorporate ecosystems into flood defence", says Iris Möller, deputy director of the University of Cambridge's Coastal Research Unit. "Rather than seeing the coast as a static line, these alternatives rethink coastlines as zones with valuable habitats such as beaches, dunes and wetlands that act as carbon stores, places for recreation and natural buffers against the waves".

Möller cites the Royal Society for the Protection of Birds' flagship Wild Coast Project at Wallasea Island in Essex, which has restored 1,655 acres (670ha) of land that had been reclaimed for agriculture years earlier back to salt marshes and lagoons. "The tide and waves now regenerate salt marsh where it had been embanked and drained. If designed well, such schemes create new habitat which can reduce the height and intensity of storm surges and lower flood risk."

It is now UK government policy to manage coastal retreat, sacrificing land to the natural process. With hard defences costing as much as £10,000 a metre, and beyond the means of local authorities, sea defences along more than 80 miles of Britain's east coast and much of west Wales may not be maintained within a few decades. As a result, it is likely that hundreds of homes, nature reserves, valuable agricultural land and even villages will be lost to the sea over the next 50 years.

"We are just one of about 50 communities on the Welsh coast which expects to be abandoned," says Matt Burrows, a flood monitor volunteer in Fairbourne, Gwynned. "The village has a low, deteriorating sea wall and it needs to be at least 2ft higher. The sword of Damocles hangs over us. In about five years' time they will stop improving the defences here and the government will start to let the village of about 400 houses go back to the sea. We are fighting the decision on every front but we are not winning yet."

Abandoning farmland and communities to the sea is expected to be emotionally traumatic but it is necessary on economic and ecological grounds, argued the UK parliament's committee on climate change in its October 2018 report, Managing the coast in a changing climate: "Building ever bigger defences to protect all coastal communities in the future would be prohibitively expensive. It would also detract from the coastal landscapes that people treasure and further interfere with the coast's natural adaptation to sea-level rise. Facing up to inevitable change requires difficult decisions.

"At risk are not just beaches," says the committee, "but 7,500km of road, 520km of railway line, 205,000ha of good, very good or excellent agricultural land, and 3,400ha of potentially toxic historic landfill."

"Sea walls used to be the big thing in the toolbox. But we know flooding will get worse. On current sea-level rise projections, sea walls that are waist high now would have to be head high by 2100 and about 18ft high by 2200. Long-term thinking is needed," says Hamish Hall, a director at global engineering consultant WSP. "I'd like to see sea defences set right back. We have a mentality to just rebuild everything after a storm. The simplest solution would be to move the infrastructure back. The problem is the obsession with building property right next to the beach, and with trying to hold the beach in place."