Coastal Adaptation in Tuvalu – Berm Top Barriers

Tuvalu is an independent island nation in the South Pacific comprising nine islands, five of which are coral atolls, and the other four are land rising from the seabed. As of 2024, Tuvalu’s population is around 11,500.

All of the Island’s land areas are low-lying, with no points higher than 4.5 metres above sea level, contributing to its high vulnerability to climate change, including sea level rise, king tides, inundation, and coral bleaching.

Climate projections under the low emissions scenario (global warming likely below 2°C) and medium to high emissions scenario show that sea levels across Tuvalu’s nine islands are projected to rise with high certainty. Sea levels are projected to rise between 24cm to 49cm under a low emissions scenario and 36cm to 60cm under a high emissions scenario.

Projected sea level rise in Tuvalu will increase wave-induced flooding, causing increased coastal erosion and inundation, with a significant increase in magnitude, duration, and frequency from 2050 onwards. Such flooding will significantly increase the salinity of soils and groundwater lenses and threaten the availability of freshwater resources. As a result, many low-lying states in the Pacific, including Tuvalu, will become uninhabitable by 2060 to 2070 under a high emissions scenario because of annual flooding.

Climate change is already impacting livelihoods, politics, and society, contributing to insecurity in Tuvalu. Sea level rise, coastal erosion, and more intense storms affect land areas, which remain a central issue in Tuvalu, with severe consequences on water, food, and people’s well-being.

Oceanic and nearshore fishing and associated subsistence and economic activities are highly at risk. These risks are considerable in Tuvalu’s already vulnerable economy, characterised by a small market, poor physical and digital infrastructure, and heavy reliance on food and energy imports.

Climate change poses a significant threat to Tuvalu’s economy, government, livelihoods, and well-being, causing uncertainty about its future survival.

Tuvalu’s climate adaptation

According to its official website, “The Tuvalu Coastal Adaptation Project (TCAP) is assisting the small island developing state by implementing measures that reduce exposure to coastal hazards in the three target islands, developing a long-term coastal adaptation strategy, building the capacity of national and local authorities to implement adaptation actions better, and investing in youth as future stewards of a resilient nation.”

“Financed with US$36 million from the Green Climate Fund and $2.9 million from the Government, the project will enable Tuvalu to take steps to manage the risks of coastal hazards.”

Constructing berm top barriers as coastal adaptation measures

Two of Tuvalu’s outer islands, Nanumea and Nanumaga, implement a novel coastal adaptation approach to reduce wave overtopping and subsequent marine flooding of the village areas. Saltwater intrusion is damaging or destroying the Island’s vegetable gardens and important crops like breadfruit, pawpaw, banana, and taro – an essential source of carbohydrates for the Tuvaluans. 

TCAP is building a berm top barrier that will raise the natural storm berm along the foreshore by an extra 1.5 metres, preventing saltwater from penetrating inland and protecting the people, their homes and crops from significant storm events. These berm top barriers will be constructed using Geotextile Mega Containers (GMC) that will be keyed into the surface of the storm berm and filled with locally sourced sediment and sand, then revegetated with native plants such as palm or coconut on each side of the angled berm. On top of the berm barrier,  A 1-metre foot path consisting of geotextile and wooden planks filled with coral rubble or sand will be constructed.

In Nanumaga, the barriers will stretch 665 metres along the coast, with a new concrete boat ramp built over the top of the berm into the village centre. In Nanumea, a 1,330-metre barrier will be built along the western coast, replacing previous infrastructure destroyed during tropical cyclone Pam in 2015.

Chief Technical Advisor Arthur Webb, who supported the design of the barriers, said: “The berm is the raised area of dune before the shore found on tropical beaches. It can be up to 30 metres high and is well behind the beach but acts as a natural storm barrier. They are a critical part of the natural ecosystem and prevent erosion. You would not want to replace them, as they are natural active buffers, protecting the land and community for free” (Smith, 2023).

“But now, the waves are of such a height that they are not only overwhelming beaches but topping over the raised berm areas, taking salt water into the villages. To protect these areas, we have raised the berms artificially,” he explained, noting that the barriers are placed in locations along the beach that are safe from the most intense energy of the sea swell, ensuring that it stays intact (Smith, 2023).

The TCAP website notes, “With the backing of the Green Climate Fund, already 7.3 hectares of new, raised land has been installed in Funafuti, providing flood-free areas for island communities. Now, plans are underway to safeguard the long-term future of the Island through state-of-the-art technology. The vision is not only to protect the small Island from physical climate threats but also to protect the precious culture and heritage of the whole community on the Island: something that, once lost, can never be replaced.”