Blue barriers: A nature-based solution to build resilience

A new tide of innovation for reef-lined coasts seeks to build coastal resilience and blue growth

Flooding and erosion are growing problems for low lying coastal zones across the world. These phenomena are expected to worsen globally by 2-3 orders of magnitude by 2100. While today coral reefs act as natural infrastructure, protecting coastal communities against wave action and storm impacts, the reefs are suffering continuous degradation. The weakening of coral reefs is not only increasing coastal risks and the cost of coastal protection and adaptation, but resulting in a loss of natural capital and biodiversity. 

For decades, the default coastal protection measure has been coastal hardening, such as rock armoring, seawalls, and shore structures known as groins. These interventions can cause erosion and often have negative impacts on coral reefs and other ecosystems that are crucial for tourism and the blue economy – i.e., the sustainable use of ocean resources for economic growth, improved livelihoods, and jobs while preserving the health of ocean ecosystem. Nature-based approaches that combine engineering with rehabilitating coral reef systems represent a new tide of innovation to build coastal resilience while protecting natural capital and boosting the economy.

"Nature-based approaches that combine engineering with rehabilitating coral reef systems represent a new tide of innovation to build coastal resilience while protecting natural capital and boosting the economy."

Surrounded by coral reefs, the Indian Ocean archipelago of Seychelles has been at the forefront of this effort. Recognizing its coastal vulnerability and understanding the protective value of this natural infrastructure against climate change impacts, the Seychellois government has been moving to improve resilience along its coasts.

A significant step in this direction was the endorsement of the national Coastal Management Plan (CMP) in 2019. The CMP proposes coral reef management and rehabilitation in 5 out of 18 priority areas, alongside other nature-based solutions and grey infrastructure -- structures such as dams, seawalls, roads, pipes or water treatment plants -- to reduce vulnerability to flooding and erosion while maintaining the beauty of the coastline.

The government and the World Bank, with funding from the Global Facility for Disaster Reduction and Recovery (GFDRR), conducted a study to develop strategies for large-scale coral reef restoration. This assessment prioritized 15 locations on the three main islands where coral restoration could reduce coastal risks and enhance biodiversity. According to the study, in most locations, coral restoration would need to be combined with artificial structures to deliver significant coastal protection. 

“Blue barriers” can build coastal resilience
Consequently, the government of Seychelles and the World Bank are exploring the potential of innovative hybrid solutions known as “blue barriers.” These measures would consist of reef structures enhanced with coral restoration and designed to induce wave breaking, reduce or redirect destructive erosional currents, and also serve as a substrate, or base, for coral colonization. The blue barrier concept can offer a multi-benefit approach: It can simultaneously provide coastal resilience, support the recovery of corals and marine biodiversity, and contribute to tourism and regenerating fish stocks.  

"The blue barrier concept can offer a multi-benefit approach: It can simultaneously provide coastal resilience, support the recovery of corals and marine biodiversity, and contribute to tourism and regenerating fish stocks. "

In the words of Alain de Comarmond, Seychelles’ Principal Secretary of Environment: “Coral reefs are critical for Seychelles, not only in terms of biodiversity, but also for coastal resilience and the development of the blue economy. The Blue Barrier concept opens up the opportunity to bring these objectives together and build a coalition of government, civil society and the private sector.”

Blue barriers involve the construction of a submerged structure using natural non-toxic materials that can serve as a stable and hard substrate for coral colonization, supporting coral recovery and the development of more biodiverse benthic communities. Although still in its infancy, coral restoration projects using artificial substrates are growing in number, and promising techniques continue to emerge. 

(A) Pilot unit made with gabion baskets and rocks in Grenade (Reguero et al., 2018); (B) Metal structure using mineral accretion technology in Maldives (Coralive); (C) 3D-printed concrete artificial reef in the Calanques National Park (Seaboost and XtreeE);  (D) MARS project: 3D-printed artificial module in Maldives (Alex Goad-MARS).

However, innovative approaches like the blue barrier are not one-size-fits-all solutions and should only be considered as an alternative for areas that meet very specific conditions. A new World Bank study in Seychelles aims to better understand the drivers of flooding and erosion and to identify effective and sustainable solutions, including the potential for blue barriers.

Hybrid solutions like blue barriers could play an important role in supporting climate resilience, especially in small island developing states, which are among the most vulnerable globally to natural hazards and climate change.

"Hybrid solutions like blue barriers could play an important role in supporting climate resilience, especially in small island developing states, which are among the most vulnerable globally to natural hazards and climate change."

“Building coastal resilience goes hand in hand with the restoration of protective coastal ecosystems,” said Brenden Jongman, World Bank Task Team Leader. “In Seychelles, the Bank and the Government are working  together to strengthen financial relief in case of a disaster through instruments like the Catastrophe Deferred Drawdown Option [which quickly releases emergency funds once a declaration of emergency is declared], with technical assistance to build coastal resilience and bolster emergency management,” he said. 

In the context of a COVID-19 recovery, nature-based solutions represent one promising way to combine development, climate, disaster risk reduction and conservation objectives.  The World Bank will continue to support innovative approaches that build resilience to hazards, contribute to sustain the economy, and protect natural capital.