All the partners at the launch call it a project, but it’s really an integrated set of projects over two years that will tackle erosion, and nutrients, and create resilience in the local environs against disaster-scale flooding. 

 

Leading the launch was the primary instigator and funder, local utility Unitywater. The project started with identifying proactive ways of offsetting the point source sediment and nutrient loads from eroded streambanks entering Moreton Bay. 

 

It will contribute to Unitywater’s sustainability goal of achieving net zero nutrients diverted to waterways by 2050. To achieve this, they bought in a long-term partner Healthy Land & Water to lead the on-ground works and bring together the diverse stakeholder groups who have an interest in and will collaborate on the project.

 

Healthy Land & Water Chief Operating Officer Dr Andrew O’Neill says this is an exciting program that allows the opportunity to deliver a large-scale set of projects to bring value to the community and restore and enhance our environment in SEQ.

 

“We are excited to work with Unitywater again and can’t wait to collaborate with Traditional Owners and other long-time stakeholders to implement cutting-edge nature-based technology to build disaster resilience and create highly liveable regions,” said Dr O’Neill.

 

“This integrated set of projects is extremely important because it will not only tackle erosion and nutrients offset, but it will also create resilience in the local environs against disaster-scale flooding.

 

"The benefits brought by innovative green engineering solutions and soft engineering approaches do not end with what we just mentioned. The works will improve water quality, and biodiversity and will promote aquatic ecosystems’ health, as well as terrestrial habitat for wildlife and regeneration of riparian vegetation," he adds when asked about the importance of the projects.

 

Sitting in a room with our very own Principal Project Engineer and Program Manager Samille Loch-Wilkinson before the launch, we learn more about the project. Samille fills us in on a bit of the background, the innovative nature-based technology involved, and how we will be able to build resilience for future generations along the Caboolture River.

Samille shows us on a map how extensive the reach of the work that will be undertaken is along the Caboolture River, stretching from the mouth of the river, near Beachmere upstream to Rocksburg. The words that come to mind are large-scale! 

 

We will be doing restoration and revegetation works that will rehabilitate 2.4 km of eroded shoreline and re-establish native vegetation.

 

Investigations resulted in nine project sites, from the upper reaches of the catchment to the estuaries of the river. It is most definitely an extensive area, and the required interventions will be different from site to site, given the different positions and hydraulic conditions along the river stream.

 

All the projects together are what we call a program. The program articulates in two main phases: on-site intensive works that will span till October 2024 followed by monitoring and maintenance works that will last for a full year.

The answer is predicted population growth. 

 

Significant population growth is forecast within the Caboolture River catchment in the coming decades and as the population grows, it becomes more difficult to provide sustainable, cost-effective wastewater services to the community. 

 

To address this, Unitywater chose the optimal strategy: investing in immediate works that reduce the number of nutrients entering the waterways, to offset forecast-increasing nutrient discharges and deliver a nature-positive outcome for the local catchment.

 

The program’s inception is based on Healthy Land & Water’s concept plans and designs proposing stabilisation works across multiple sites along the tidal reaches of the Caboolture River. The works consist of innovative green engineering solutions, and soft engineering approaches which include log revetment, bank reprofiling, and revegetation. These works will enhance aquatic values whilst still delivering bank stabilisation and erosion prevention. 

This program will contribute to protecting the health of the Caboolture River with actions that will reduce threats to the environment, enhance biodiversity, and build flood resilience.

Learning about all the innovative ways in which Healthy Land & Water addresses threats and restores landscapes and biodiversity is incredibly interesting.

By stabilising riverbanks, we will prevent their erosion and the consequent sediment and nutrient loads entering the waterways. At the same time through revegetation, we will increase biodiversity along the waterways and provide natural resilience to future flood and waterway erosion. 

 

In addition, native vegetation and some of the nature-based solutions implemented in the works will improve water quality, and biodiversity and will promote aquatic ecosystems’ health, as well as promote terrestrial habitat for wildlife and regeneration of riparian vegetation. 

Each site will see its own solutions being implemented, depending on the specific needs of the area.

 

We have four main types of works that will be combined accordingly: earthworks to stabilise riverbanks incorporating tidal benches that will promote the natural revegetation of mangroves, mangrove seeding and native vegetation planting, coil logs, and timber root balls.

 

The works will mitigate the impact of different threats along the river stream. Here are a couple of examples of how we will use the types of works:

 

• Riverbank stabilisation & revegetation.

The current shape of the riverbank is highly eroded, and vertical, and does not allow for vegetation growth. These banks are highly susceptible to further bank erosion from boatwash and floods. The solid blue line represents the tidal river level and the dashed ones the tide levels.

 

Healthy Land & Water will batter the vertically eroded bank and create a bench on the riverbank that will allow us to plant mangroves. This tidal bench will allow mangroves to have optimal conditions for survival. To make work even more efficient, we will relocate any existing plants and add more where needed.

 

In addition, as you can see in the diagram below, to stabilise the riverbank and protect it from erosion and boat wash we will place a coir log and timber logs with a root ball horizontally that will be kept in place by timber piles (placed vertically as per diagrams) and large boulders. 

 

The root balls will act as a protector for the riverbank against waves and floods and will act as a trap for sediment as well as provide improved aquatic habitat for fish and other aquatic life.

 

• Revegetation with BESE-Elements®

Healthy Land & Water will be utilising an innovative, worldwide acclaimed technology that was invented in the Netherlands. Healthy Land & Water has used BESE-Elements for other restoration projects including Lungfish habitat restoration and the Pumicestone Passage shellfish habitat restoration, each project delivering highly successful outcomes. 

They are effective, cutting-edge, and nature-based!

 

   

 

As you can see from the photo above, this incredible product is a 3D matrix. The grids are made entirely out of a waste product, potato starch, and fully biodegrade within 5 to 10 years.

 

They act like a temporary structure to start ecosystem restoration. They are perfect for retaining plant seeds (propagules), supporting the colonisation and growth of saltmarsh plants and mangroves, restoring marine ecosystems like shellfish reefs, and trapping sediment that can flow in the waterways, purifying the water.

Once established, the mangroves provide a structure on their own, and the grids break down leaving behind the re-established ecosystem.

We had the chance to do our in-situ trials for this project with the BESE-Element creators themselves when they came to Australia, and it was exciting to collaborate! Check out their incredible products here.

We will take the mesh sheets and clip two layers together, then we will scatter mangrove propagules on them and clip a third layer on top of the seeds to retain them within the structure.

As shown in the diagram below, the structures (grey line) will then be secured on the riverbank, along with coir logs to prevent them from being washed away by tides and boat wash.

 

 

The mesh ensures that the propagules do not disperse in the water flow and will give them a higher chance to germinate and grow. Furthermore, the BESE-Elements® can catch other seeds brought downstream during the high tide and trap sediment and nutrients.

We are proud and excited!

We cannot wait to see it all coming to fruition and to contribute to mitigating threats and building flood resilience along the Caboolture River.

We are proud to be collaborating with Kabi Kabi and Bunya Bunya Aboriginal Corporations and our staff have been trained to make sure Cultural Heritage is preserved.

This project will provide offsets for the equivalent of an additional load on Unitywater’s wastewater infrastructure of 5,500 people, it will see more than 30,000 seedlings planted, 1.6 tonnes of nutrients offset per year, and 34 tonnes yearly carbon offset from Unitywater’s Burpengary East wastewater treatment plant.

 

Exciting times await us!

 

ACKNOWLEDGEMENTS
Kabi Kabi Aboriginal Corporation.
Bunya Bunya Aboriginal Corporation.
City of Moreton Bay.
BESE Ecosystem Restoration Products.
Barung Landcare.

Various local private landholders/leaseholders.

Works engineering was designed by Alluvium Consulting.

This project is delivered by Healthy Land & Water with funding from Unitywater.