Did you say 283 metres? The Lower Caboolture Project sprinted out of the starting blocks, and has now reached its largest site
Since it broke ground, the restoration journey along the Lower Caboolture River has made big strides with mangroves growing, riverbanks holding it together and work now in full swing at the largest site of the program which is 283 metres long!
Flood resilience Restoring riverbanks and reducing streambank erosion increases the resilience to major floods. |
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Increasing biodiversity and habitat The solutions implemented improve biodiversity and promote aquatic ecosystems’ health, terrestrial habitat for wildlife and regeneration of riparian vegetation. |
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Cleaner water Containing and controlling erosion and sediment flowing downstream ultimately increases water quality. |
When we messaged our team asking where they were recently, we received a photo of a huge excavator… We wanted to know more and had to dig deeper (pun intended)!
Breaking ground at the largest site of the program
Our team has been with our contractors at the largest site of the Lower Caboolture Resilience and Nutrients offset program, working on a 283-metre-long section of river bank along the Lower Caboolture River.
The Lower Caboolture program is restoring 2.4 km of bank at nine sites along the Lower Caboolture River, each requiring a unique set of green engineering solutions tailored to its specific issues and characteristics.
At this site, the highly eroded and vertical riverbank does not allow for vegetation growth and the shape of the bank makes it very susceptible to further erosion from boatwash and floods. A picture tells 1000 words, and the images below show it well.
Considering the task at hand, the solution chosen by the team is to batter the vertically eroded bank and create a bench to allow mangroves to establish and for us to get in and plant native species along the banks. This tidal bench will enable the plants to have optimal conditions for survival.
To stabilise the riverbank and protect it from erosion and boatwash we will place coir logs and timber logs with a root ball that will be kept in place by timber piles (placed vertically as you can see in the below diagrams), together with 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.
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 and habitat along the waterways, promote aquatic ecosystems, improve water quality and provide natural resilience to future flood and waterway erosion.
Come on site 24 with us: photo story
We asked the team to tell us what they are up to at site 24.
They say it is important to set up for success, which they’ve been doing through years of planning and site preparation to ensure our works posed no additional risks to the environment or community. This has involved working alongside the Kabi Kabi Peoples to ensure safe handling of cultural heritage finds and preservation of cultural values. Our construction environmental management plans, erosion and sediment controls and compliance measures go through a rigorous approval process with Federal, State and local government agencies.
Due to the length of the site, we have broken it down into three separate portions. The works are rolled out across each portion in turn.
We’ve already started removing soil from the riverbank to reshape it with some big excavators. The battering of the bank involves removing 6809 cubic meters of soil and creating the perfect height within the tidal range to enable mangroves to establish.
Interesting facts:
- This amount of soil corresponds to roughly 340 trucks loads.
- The soil that is sent offsite to be treated so that it can be reutilised on other projects.
Once the desired shape was achieved, it was time to lay down all the logs.
And this is how it looked once the bank was battered and logs were positioned and pinned.
Plating is underway on the first portion of the site.
Over the whole site, the riverbank will be covered with 8322 native plants, including 238 mangrove propagules which will be distributed on the bench.
We can’t wait to share some updates on this site with you all in the upcoming months.
Speaking of updates and progress
We are taking this chance to share an update on some other sites where revegetation has been completed and the sites are now transitioned from the development phase to monitoring and maintenance, which is carried out regularly to ensure that there is no structural failure or loss of vegetation.
These sites have undergone riverbank reprofiling and battering, installation of logs and revegetation.
Site B1 - At the beginning of July 2023, major earthworks commenced at this site, as the dedicated team broke ground for the restoration mission.
Fast forward to this year, mangrove propagules have established and the native species have grown tremendously already.
Site 5 - An earlier site (site 5) has seen mangroves and plants establish strongly on the bank.
On anther site we’ve been working on (Site 6), we used bog mats to stop the excavators from sinking into the soft ground and reduce the disturbance to the site. In addition, the bog mats protected the saltwater couch (Marine Plant) which meant that a lot of it was able to survive the earthworks component of the site restoration.
You can read the full project snapshot here.
Acknowledgements
Kabi Kabi Aboriginal Corporation.
Bunya Bunya Aboriginal Corporation.
City of Moreton Bay.
BESE Ecosystem Restoration Products.
Barung Landcare.
Klan Bros Earthmoving.
Various local private landholders/leaseholders.
Works engineering was designed by Alluvium Consulting.
This project is delivered by Healthy Land & Water with funding from Unitywater.