Breakwater protection for Marsalforn will damage seagrass

A new coastal defence project in Marsalforn Bay, Gozo, is set to bring significant changes to the area, promising better protection from storms and the restoration of the long-eroded beach.

But an environment impact assessment reveals that the construction of two new breakwaters and rubble groynes will come at a cost to the marine ecosystem, as around 10,300 square metres of protected Posidonia Oceanica seagrass – which play a critical role in supporting marine life and maintaining the health of coastal waters meadows – are expected to be permanently lost.

Marsalforn Bay, with its wide, open mouth facing the northwest, is highly susceptible to storm surges and flooding, especially during the harsh northeast and northwest winds prevalent in the region. The current coastal defences are considered inadequate, leaving the seafront and nearby properties exposed to significant damage during storms and heavy rainfall events.

Water from the Marsalforn Valley flows rapidly through the village, compounding the flooding and leading to frequent infrastructure damage. The proposed coastal defence system is designed to mitigate these issues through the reconstruction of the Santa Marija breakwater and the addition of the new Menqa breakwater, along with two rubble mound groynes.

The structures aim to reduce wave impact, control sediment transport, and create a stable shoreline that can support an extended and replenished beach. If the project goes ahead as planned, the seafront will be far less vulnerable to the destructive forces of storms, thereby protecting local businesses and improving the overall safety and usability of the bay area.

Project to cover seabed

The centrepiece of the project, the Santa Marija breakwater, will extend 207m into the bay and cover an area of 10,421 square metres on the seabed. Constructed using a combination of concrete caissons, natural rock, and concrete armour units, the breakwater is designed to withstand the powerful wave forces that currently batter Marsalforn.

The structure will also feature a walkway for pedestrians, providing a new recreational space for locals and visitors to enjoy scenic views of the bay.

In contrast, the Menqa breakwater, at just 91m long, will be built using a simpler rubble mound design. Together, the two breakwaters are expected to transform the water dynamics within the bay, calming the strong currents and minimizing the risk of erosion along the shoreline.

To further control sediment movement and support beach replenishment, two rubble mound groynes will be constructed on either side of the Marsalforn valley’s mouth. The groynes, standing up to 4m high and covering 932sq.m, will help stabilise the newly extended beach area, which will span an additional 3,084sq.m. This enhancement is expected to restore the bay’s sandy shoreline to a more stable condition, bringing it closer to its historical form.

Ecological concerns: loss of Posidonia meadows

While the breakwater and groyne construction promise enhanced coastal protection and beach restoration, the EIA report from AIS highlights a major ecological drawback: the irreversible loss of Posidonia Oceanica meadows.

These underwater meadows, often referred to as the “lungs of the sea” for their role in producing oxygen and supporting marine life, will be significantly impacted by the construction. The Santa Marija breakwater alone is expected to destroy around 10,300sq.m of these habitats, which are not only protected at a national and European level but are also listed as endangered under the Barcelona Convention.

The loss of Posidonia meadows is of critical concern because of their slow rate of natural recovery. The EIA notes that recolonisation can take decades, if not longer, making the impact effectively permanent. This loss is particularly troubling given that these meadows provide refuge and foraging grounds for numerous marine species, including fish that are important to the local fishing industry.

To mitigate the damage, the EIA recommends considering compensatory measures such as transplanting adult Posidonia plants or planting seeds in degraded areas around the site.

However, these options are fraught with challenges. Transplantation is a costly and labour-intensive process with unpredictable survival rates, while seed planting requires controlled conditions that are difficult to replicate in the open sea. As a result, even the most well-executed mitigation efforts may not fully compensate for the loss.

Visual impact on Marsalforn’s seascape

Beyond the ecological implications, the new breakwaters will also transform the visual landscape of Marsalforn Bay.

The EIA categorises the impact on key viewpoints as “major adverse”, noting that the imposing presence of the breakwaters will disrupt the natural openness and visual flow of the bay.

The extension of the coastal promenade into the bay will be highly visible, altering the character of Marsalforn’s previously unobstructed maritime environment. Additionally, the improved shelter provided by the breakwaters is likely to attract more vessels to the area, potentially resulting in visual clutter and congestion.

Modifying water circulation

The construction of the breakwaters will also alter water circulation patterns within the bay, with both positive and negative consequences.

On the positive side, calmer waters will lead to a reduction in wave-induced erosion, making the shoreline more stable and reducing the risk of infrastructure damage. Sediment from the Marsalforn Valley will settle more quickly, which could increase the available sandy beach area over time.

However, these changes will also mean that floating debris and waste discharged during heavy rain events could become trapped within the bay, leading to potential water quality issues. The breakwaters will disrupt the bay’s natural flushing mechanism, potentially affecting marine habitats and water clarity.