Coastal Communities Facing the Threat of Climate Change
The Pacific Island countries are now facing a new threat to their survival due to climate change. Small low-lying atoll countries, as well as the coastal populations of the small island countries, are constantly threatened by the impacts of a changing climate. With the rise in sea levels, coastlines are eroding, and villages, houses, burial grounds, arable land, and other critical infrastructure are gradually being washed away.
For many of these vulnerable coastal communities, the only option seems to be relocating the entire population to higher ground. However, this is an extremely costly solution that goes against the best interests of the communities. Relocation not only means moving houses and people but also breaking away from the ancestral grounds and cultural heritage that are deeply rooted in these coastal regions.
An Alternative Solution: Nature-Based Seawalls
Instead of turning to expensive and environmentally-disruptive concrete seawalls, governments can consider an innovative nature-based solution (NbS) to protect their coastal populations. This paper provides a model NbS seawall design that is environmentally, ecologically, and culturally responsible, while also being a fraction of the cost of traditional “grey” infrastructure.
By using nature to address a problem caused by nature itself, these NbS seawalls offer a sustainable approach to coastal protection that can save millions in government funding, rehabilitate the local environment, and preserve the cultural identity of threatened communities.
Fiji’s Coastal Erosion Challenges
As a small island nation, Fiji has faced significant challenges in keeping its coastal communities safe from the drastic effects of climate change. With a population of 870,000 and 332 islands, about one-third of which are inhabited, Fiji is highly vulnerable to sea level rise, coastal erosion, and other climate-related impacts.
The country’s tourism sector, a critical driver of the economy, is heavily dependent on the health of the surrounding seas, coral ecosystems, and marine biodiversity – all of which are under threat from climate change. Inland resources, such as the extensive network of waterways, are also being impacted by issues like flooding, siltation, and debris buildup.
In response to these mounting challenges, the Fijian government has developed several strategic documents and policy frameworks to guide its climate change mitigation efforts. However, the actual implementation of these plans has been hindered by external shocks, such as the COVID-19 pandemic, as well as a lack of sufficient financial resources.
The Nature-Based Solution Seawall Design
To address the coastal erosion crisis in a more sustainable and cost-effective manner, the Fijian Ministry of Waterways has designed and constructed a nature-based solution (NbS) seawall, transitioning from traditional “grey” concrete structures to a more environmentally-friendly, boulder-based approach.
The NbS seawall design incorporates four key components:
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Mangrove Forests: The first line of defense is a tidal forest of mangroves (Rhizophora mangle), which serve as natural wave breakers and provide critical habitat for marine life.
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Boulder Protection: Between the mangroves and the soil wall, rows of large, durable boulders are placed to act as a barrier and help prevent erosion from wave action.
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Soil Wall: A wall made of either clay soil or rotten rocks is constructed, standing at least 2 meters above the highest tide level.
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Vetiver Grass: At the top of the wall, rows of vetiver grass (Chrysopogon zizanioides) are planted, creating a natural, solid barrier that helps anchor the soil and shield against storm surges and floods.
By integrating these four elements, the NbS seawall provides a robust, nature-based solution for coastal protection that is not only cost-effective but also ecologically and culturally responsible.
Benefits of the NbS Seawall Approach
The Fijian government’s implementation of the NbS seawall model has yielded several key benefits:
Cost Savings: Constructing an NbS seawall costs approximately $20,000 per 100 meters, compared to $250,000 for a traditional concrete seawall of the same length. This represents a significant cost savings for the government, allowing them to protect a greater stretch of coastline.
Environmental Rehabilitation: The NbS seawall design actively contributes to the restoration and expansion of natural habitats, such as mangrove forests and marine ecosystems. This helps to rebuild the region’s biodiversity and natural capital, which is crucial for long-term sustainability.
Cultural Preservation: By avoiding the need for mass relocation of coastal communities, the NbS seawall allows these populations to maintain their ancestral ties to the land, preserving their cultural heritage and way of life.
Scalability: As of 2022, the Fijian government has identified 108 sites requiring NbS seawall construction, covering a total length of 38.18 kilometers. The relatively low cost and ease of implementation make this approach highly scalable for addressing the nation’s coastal protection needs.
Constructing the NbS Seawall
The process of building an NbS seawall involves several key steps:
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Mangrove Planting: Mangrove seedlings are planted in rows, with the spacing and angle of the rows determined by the specific wave conditions of the site.
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Boulder Placement: Durable, angular boulders ranging from 800-1200 mm in diameter are placed between the mangroves and the soil wall, creating a natural barrier.
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Soil Wall Construction: A compacted wall of either clay soil or rotten rocks is built, standing at least 2 meters above the highest tide level.
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Geotextile Fabric: A geotextile fabric, such as Bidim A29, is spread between the boulder layer and the soil wall to help prevent erosion.
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Vetiver Grass Planting: Rows of vetiver grass are planted at the top of the wall, with the tillers spaced approximately 10 cm apart.
By carefully integrating these different components, the NbS seawall is designed to provide effective coastal protection while also enhancing the local environment and preserving the cultural identity of the affected communities.
Conclusion: A Nature-Based Solution for a Nature-Driven Problem
As coastal communities around the world continue to face the threats of climate change, it is clear that innovative, sustainable solutions are needed to address these challenges. The nature-based solution seawall design implemented in Fiji offers a compelling model for other nations to consider, providing a cost-effective, ecologically sound, and culturally responsible approach to coastal protection.
By harnessing the power of nature itself, this NbS seawall not only safeguards vulnerable communities but also helps to restore and expand the region’s natural capital, benefiting both the environment and the people who depend on it. As the impacts of climate change continue to intensify, it is crucial that governments and communities explore such nature-based solutions to build resilience and ensure a sustainable future for all.
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