Nature-based solutions for coastal protection
Humans and associated infrastructure in the coastal zone are threatened by hazards, such as erosion and flooding. The severity of these coastal hazards is predicted to increase with rising sea levels and more frequent storm events resulting from future climate change. Although traditional coastal infrastructure (e.g. seawalls and breakwaters) is still the “go to solution” for coastal protection, there is growing recognition these structures are not economically or environmentally sustainable. Novel solutions are needed for the resilience of coastal communities to climate change in the coastal zone.
In responses to these coastal hazards, there is growing interest in applying ecological engineering principles – combining engineering and ecological objectives to develop infrastructure that benefits both humans and nature. Natural, created or restored habitats such oyster reefs, macroalgal canopies, mangroves and saltmarshes have the potential to provide coastal protection as well as enhancing biodiversity and other ecosystem services (e.g. food provision, improved water quality). This working group will develop and test the efficacy of nature-based coastal defence solutions in protecting coastal communities from flooding and erosion. The research is being undertaken in collaboration with local land managers and relevant government bodies to provide better information on how ecological engineering can be incorporated into coastal defence planning for enhanced hazard risk reduction.
Project 1: Created mussel reefs
In this project we are constructing an offshore breakwater of steel cages filled with local rock and recycled mussel shell to protect residents in Portarlington, Port Phillip Bay from persistent erosion and flooding. We are trialling different methods to seed the breakwater with native mussels, with the aim of creating an entire mussel reef for coastal protection. Ongoing monitoring will measure the success of the reef for reduction in wave height, accretion of the shoreline and other co-benefits expected from a mussel reef, such as increased biodiversity and improved water quality. This project is funded by DELWP’s Port Phillip Bay Fund. This project is a collaboration with City of Greater Geelong Council.
Project 2: Planted mangroves and concrete pots
In this project we have designed 3D-printed concrete pots to plant mangroves. The pots are designed to attenuate wave energy while the mangroves establish and grow. Adult mangroves will then provide natural coastal protection against waves and stabilise the sediment. Given that this approach will either create new or restore existing blue carbon habitats we will evaluate how much additional carbon will be stored in these systems because of project implementation.
This project is funded by DELWP’s Climate Change Innovation Grant. This project involves a large collaborative team of local and state government bodies, community engagement specialists and an industry partner.
Project 3: Mangroves and rock fillets
A common hybrid approach for coastal protection is the use of rock fillets (a line of rocks placed on top of each other) in front of natural or planted mangroves or saltmarsh. These rock fillets are used promote mangrove establishment and have been widely implemented in New South Wales, but there is little research in their blue-carbon co-benefits. In collaboration with NSW DPI and Southern Cross University, we are collecting data on one new rock fillet, and using existing fillets to quantify their efficacy at accreting sediment, sediment carbon and biomass carbon.
Project 4: Natural vegetated habitats (seagrasses, mangroves and saltmarshes)
Global studies suggest that natural vegetated habitats can provide important protection against erosion and flooding. However there is limited information about the extent of coastal protection provided by these habitats in temperate regions such as Victoria. For this project, we are measuring wave attenuation of intact seagrass beds, mangroves and saltmarshes in various locations around Port Phillip and Western Port Bays. In addition, the protection provided by these habitats is being compared for cost-effectiveness to traditional engineering solutions i.e. seawalls.
Project 5: Mussels and ropes
In this project we are working with harbour managers to develop new methods for growing mussels on pier pilings in urban marinas. These pier pilings replace natural habitat in the bay and are hotspots for invasive species. We are measuring the effectiveness of these mussels in preventing colonisation of invasive species, improving native biodiversity and water quality in a marina. This project is being run in collaboration with Wydenham Harbour.