A submerged breakwater in Avlékéte en Ouidah, Benin

Around the world, coastal ecosystems are under pressure. The culprits? Climate change, human activities and extreme weather events. Tropical countries, such as West African ones, are especially vulnerable. In Benin, for instance, the Atlantic Ocean swallows up more and more land. This not only threatens houses, ports, but also causes floods, and soil erosion. Insert a nature-based underwater breakwater we finalised in 2021. This to reduce erosion but also to ensure a safer area for swimming and maybe a hotspot for life underwater.

Early 2018, we started extensive coastal protection works off the coastal town of Avlékété. The government of Benin commissioned this project.

We designed and built a submerged breakwater parallel to the coast in combination with sand replenishment. The underwater breakwater ensures that waves continue to reach the coast but with less energy. In this we have been inspired by nature: coral reefs. These are also situated in the shallows and just off the coast.

Nature-based solutions

The 5-kilometre-long submerged breakwater is a great example of a Nature Inspired Design. By imitating the shape of a barrier reef, we provide coastal protection but also create the basis for a rich and thriving ecosystem. By giving Nature Inspired Design a key place from the start of the project, we were able to encourage biodiversity and improve the natural environment around the project.

Benin in numbers

5

km breakwater

We built a 5-kilometre-long underwater breakwater

3

years

We realised the project in 3 years time

1.2

million tonnes

We installed boulders from 1 to 3 tonnes, in total 1.2 million tonnes

2.5

million m³

We delivered 2.5 million m³ of sand to widen the beach

Did you know

Because the dike is submerged, the view of the horizon will not be disturbed. From the beginning, we worked on maintaining that aesthetic character, which is very important in the context of the government plans to fully develop coastal tourism in Benin.
The dyke is 150 metres from the shore.
Rock installation vessel Pompei positioned the boulders for the breakwater and a trailing suction hopper dredger dredged and reclaimed sand to restore the affected beaches.
Before the project kicked off, engineers carried out the necessary studies and demonstrated, based on model tests, that this concept is sustainable and that it works.
Three years after finishing the project, we continue to research the long-term impact of the five-kilometre-long submerged breakwater on the marine environment, the coastal protection and the socio-environmental dynamics.

Project video

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