Dezeen Magazine

Erosion Mitigation Units form a break water 60 meter offshore

Reef Design Lab crafts Erosion Mitigation Units from recycled oyster shells

Melbourne studio Reef Design Lab has created a series of organically shaped modules from concrete blended with oyster shells to help reduce coastal erosion in Port Phillip Bay, Australia.

The Erosion Mitigation Units (EMU), which have been longlisted in the Dezeen Awards sustainable design category, were used to build a breakwater to reduce coastal erosion and designed to create a habitat for marine life.

Erosion Mitigation Units are semi-submerged modules
Erosion Mitigation Units are semi-submerged modules

Designed for the City of Greater Geelong municipality by Port Phillip Bay, the two-metre-wide EMU modules form a permeable barrier 60 meters offshore, where the water depth ranges from 30 to 130 centimetres.

Reef Design Lab opted for an organic shape to minimise the material use and maintain structural integrity while creating refuges and colonies for ocean life.

A snorkeler is visiting the EMU breakwater
The breakwater is a snorkelling destination

The design team used digital moulding analysis alongside traditional casting techniques to produce the precast reusable moulds in its Melbourne studio.

This saved a significant amount of cement compared to using 3D concrete printing, according to the studio.

Reef Design Lab also added locally sourced oyster shells, which it says makes for an ideal surface for shellfish, as aggregates in the concrete mix to manufacture the EMU modules.

The geometry of the modules was optimised to create the habitat conditions needed for marine species to live on them.

An overhang provides resting space for stingrays and pufferfish, while tunnels and caves on the module shelter fish, octopus and crustaceans from predators and provide shaded surfaces for sponges and cold water coral to grow on.

The module shelters fish from predators
The module shelters fish from predators

The module's surface was designed with one-centimetre-wide ridges and made rough on purpose to reveal the shell aggregate and attract reef-building species such as tube worms, mussels and oysters.

Designed to be covered in small pools, the modules retain water and shelter intertidal species at low tide.

Reef Design Lab installed 46 modules of EMU in six hours
Reef Design Lab installed 46 modules of EMU

In October 2022, Reef Design Lab installed 46 EMU modules in Port Phillip Bay. The breakwater is being monitored by the Melbourne Universities Centre for Coasts and Climate for the next five years.

Six months after the installation, species including shellfish, sponges and cold water corals were colonising the modules, the studio said.

Another breakwater project that aims to fulfil engineering and ecological requirements is the Buoyant Ecologies Float Lab in San Fransisco Bay by a team at the California College of the Arts.

Off the coast of Cannes in France, British sculptor Jason deCaires Taylor created the Underwater Museum of Cannes, a collection of six large underwater sculptures, to call for more care for ocean life.

The photography is courtesy of Reef Design Lab.

More images

A snorkeler swimming by EMU
A snorkeler swimming by EMU
Oyster shells are blended in concrete for the manufacture of Erosion Mitigation Units