Bringing back the mangroves: Bank stabilisation and water quality in the Caboolture River (#12)
Margie Dickson
1
,
Misko Ivezich
2
- Healthy Land & Water, Brisbane, QUEENSLAND, Australia
- Alluvium, Australia
- This project involves 2.4km of riverbank stabilisation in a tidal zone. The long-term restoration strategy is to re-establish a mangrove fringe.
- Works are funded by the local water utility (Unitywater) under a nutrient offset policy framework.
- Bank stabilisation works were designed by Alluvium. Healthy Land and Water is responsible for project scoping and on-ground delivery.
- The area has high fish habitat value, so rock toe protection is not permissible. A timber-based approach protects the sites from ongoing erosion and improves habitat.
- The eroding banks were reprofiled to create a suitable “bench” zone to establish mangroves. Logs were pinned into the bench to protect the mangrove propagules until they grow large enough to form a resilient forest.
- The presentation shares observations and learning from the perspectives of the lead design engineer and the site engineer.
- Three sites were complete by January 2024, when they experienced their first flood. This was an encouraging first test of the bank stabilisation approach. Young mangroves, bank plantings and log structures all coped well with the event.
- Features supporting natural mangrove recruitment have been identified and emphasised in subsequent sites.
- Mangroves often co-exist with high-risk acid-sulphate soils (ASS). The project was able to adjust the earthworks profile to reduce ASS risks and successfully treated ASS spoil on site.
- Mangrove restoration can improve resilience of waterways and infrastructure to impacts of flooding and sea level rise. This project has developed establishment approaches which we hope will assist others working in similar ecosystems.
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