Mangroves and Floating Breakwaters for Coastal Protection

Floating mangrove breakwaters are emerging as a powerful, sustainable alternative to concrete sea defenses. 

According to a recent review in Ecological Engineering, these natural systems can cut wave energy by up to 80%, providing significant protection for marinas and coastal areas.

The Problem: Rising Sea Levels and Coastal Erosion

Human-induced global warming is causing sea levels and temperatures to rise, leading to more frequent and intense coastal flooding, erosion, and storm damage. Traditional "hard" structures like seawalls and rock revetments can protect coastlines but often harm ecosystems and reduce public beach access. This has led to a growing interest in "soft" or nature-based alternatives, such as restoring mangrove forests and creating living shorelines, which provide both coastal defense and ecological benefits. However, these natural solutions can be vulnerable to severe storms and long-term sea-level rise.

The Promise of Floating Breakwaters

Floating breakwaters are structures that reduce wave energy and protect nearshore areas. Unlike their traditional bottom-founded counterparts, they are not affected by water depth or seabed conditions and can be easily moved. They dissipate wave energy through reflection and turbulence. Research has shown that floating breakwaters can be highly effective, with various designs, such as box-type and pontoon-type, successfully reducing wave height. Some innovative designs, like the kelp-box-type, have shown even better performance by integrating plants to enhance wave attenuation.

Mangroves: Nature's Coastal Engineers

Mangroves are crucial coastal ecosystems known for their ability to protect shorelines. Their intricate root systems, trunks, and branches work together to slow down waves, trap sediment, and prevent erosion. They also offer significant ecological benefits, acting as carbon sinks and providing habitats for a variety of marine and terrestrial species.

Research on different mangrove species reveals varying levels of wave attenuation. Field, laboratory, and numerical studies have shown the following wave reduction coefficients:

• Rhizophora: 80%
• Avicennia officinalis: 55%
• Sonneratia: 50%
• Kandelia candel: 20%

The species with the most complex root systems, like Rhizophora, tend to be the most effective. The effectiveness of mangroves is also influenced by factors such as forest width, density, water depth, and wave characteristics.

Floating Mangroves: A Hybrid Solution

Integrating mangroves with floating breakwaters presents a promising hybrid solution. This approach combines the protective benefits of both structures, creating floating mangroves that are detached from the shoreline and suspended on the water's surface. This innovative concept could be particularly useful in areas with limited space for traditional mangrove restoration or in deep waters.

Several small-scale models and feasibility studies have demonstrated the potential of floating mangroves. They can provide wave attenuation, carbon sequestration, and erosion control while also being relocatable and durable. However, further research is needed to rigorously test their effectiveness, especially in large-scale prototypes.

Key challenges include:

• The need for more precise data on wave attenuation.
• Potential for shading and disturbing native benthic vegetation.
• Technical and financial challenges of large-scale deployment.

Overall, the development and testing of floating mangrove structures are crucial for creating effective and sustainable solutions to combat the growing impacts of climate change on coastal zones.

Access Griffith University’s team report – Are floating mangrove breakwaters effective for wave attenuation? – A Literature Review: Click Here

Risheharan, K., Baumeister, J., & Adame, M. F. (2025). Are floating mangrove breakwaters effective for wave attenuation? - A literature review. Ecological Engineering, 211.