Rethinking coastal infrastructure protection
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As environmental factors weigh ever heavier in infrastructure projects, authorities are exploring some unusual methods to protect their ports, seafront towns and coastlines. And with some options offering lower costs and less destruction of marine habitat than traditional hard engineering solutions, contractors will likely need to familiarize themselves with a wide range of non-conventional defences in the future.
Coastal defences play several important roles, from reducing erosion and flooding to providing calm waters that enable easier maneuvering and berthing for vessels. But could they also play a role in preserving sea life? One example currently under investigation highlights the forward thinking being deployed in the sector, as well as the search for an environmental and economic win-win.
Resuscitating reefs with 3D printing
Coral reefs are the original natural coastal defence, and their success in protecting shorelines from erosion has been replicated by a proliferation of artificial offshore reefs at beaches and harbours across the world. But natural reefs are under threat. Pollution, sedimentation, unsustainable fishing and climate change have all played a part in degrading reefs significantly in recent years. Coastal development and dredging can also harm reefs and the delicately balanced ecosystem around them – nearly 25% of the world’s fish depend on healthy coral.
It was the latter motivation that spurred researchers at a group of Israeli universities to propose an innovative solution: supplementing damaged reefs with artificial, 3D-printed reef to encourage coral - and the ecosystem that relies on them - back to health.
The process begins by scanning underwater photographs to develop a three-dimensional model of the reef, which is then enriched with genetic data, enabling scientists to learn the complex form of the reef and how it encourages fish to live there. A naturally porous ceramic is used to print new structures that can be installed to bring reefs back to life – reclaiming their crucial role in both biodiversity and coastal protection.
The innovation is based on reefs off the southern Israeli city of Eilat, but the model is adaptable to other marine environments and could help curb reef devastation – and prevent coastal erosion - around the world.
Using nature’s building blocks
Taking inspiration from nature – and even giving it a helping hand – is a rapidly evolving area of coastal defence strategy. In 2021, CEDA News covered the Coastbusters coalition’s pioneering exploration of engineered textiles to provide habitat for ‘ecosystem engineering species’; living organisms including seaweed, sand worms and mussels that create environments which help to reduce coastal erosion and reduce the force of waves.
Reporting on the early phase of its research, Coastbusters – which includes Jan de Nul as one of its members – suggested that a new way of thinking was needed to bring nature-based solutions into mainstream coastal defence planning. In particular, the partners wondered how to value the natural resources that could help protect coastlines.
A recent study from the National University of Ireland in Galway does just that. The research compared the cost-benefit of a natural reef built from oysters – prevalent along the Galway coast - to a conventional seawall. Around 200 tonnes of empty Pacific oyster shells were used to cover a 50-metre radius and one metre in height from the seabed, which was then seeded with native oyster stock.
The research found that both options resulted in a positive net benefit over a 20-year time horizon. However, the study found the nature-based solution had a benefit-cost ratio multiple times larger than the ‘grey infrastructure’ seawall.
While the use of such nature-based solutions has wide applicability, it is not free from challenges. Ecosystem conditions, available space and local stakeholder support are all necessary elements. Properly valuing a location’s natural protection also requires a holistic approach to understanding the economic impact of coastal defence projects. As such natural solutions are likely to be integrated into conventional coastline management, rather than replacing it.
Assessing the alternatives
The Galway study is an unusual example of financial analysis around the benefits of natural coast management, and the lack of widely recognized means to assess the true economic impact of nature-based solutions is a key obstacle to scaling up such initiatives. In November 2021 the UK Engineering and Physical Sciences Research Council (EPSRC) awarded a grant to researchers at the University of Liverpool to remedy this fact.
The justification for the grant again highlights the pressing need for cost-effective, sustainable defences. Researchers argued that in the UK coastal flooding causes around £260 million of damage each year. Huge swathes of national infrastructure are also at risk from coastal flooding: 41% of power stations, 17.9% of railway track, 14.3% of railway stations and 33% of wastewater treatment – not to forget around 500,000 private properties.
“Hard engineering solutions are becoming economically unviable due to the high costs of construction, maintenance and adaptation to changes in sea level and storms,” the researchers note.
Nature-based solutions could hold an answer. But, the researchers add, there are no “quantitative and process-based decision-making tools and guidelines to aid engineers, planners, and governments to select coastal management strategies fit for their unique local environment”. Further, there are also uncertainties about the conditions needed to establish such solutions, how to maximise their lifetime and any meaningful quantification of their effectiveness.
The EPSCR grant-funded project plans to remedy these knowledge gaps, using remote sensing, artificial intelligence and computer modelling to develop criteria for coastal protection using engineering with nature. At the same time the research will establish the knowledge needed to choose the most durable and efficient coastal management types and location. The project aims to provide UK authorities with a solid base from which to plan defences to meet anticipated rising sea levels increasing severe weather in a sustainable, natural way.
The idea of natural coastal defence is not new, but perhaps its time has come. New technologies – from artificial intelligence to geo-engineered textiles to 3D printing – will have an important part to play in accelerating uptake. As interest grows, contractors traditionally charged with deploying concrete and sand will need to add new, natural tools to their armoury.
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