South East Queensland flooding brings a new wave of marine pollution to Moreton Bay Ramsar Wetlands

The flood plume from the 2022 SEQ floods entering southern Moreton Bay (Sentinel-2 imagery from European Space Agency).

The recent flooding in South East Queensland (SEQ) caused widespread devastation throughout the region, including tragic loss of life and extensive damage to homes, business, infrastructure and the environment. As Queenslanders begin the lengthy process of rebuilding, we are still working to uncover the full impact of this flood event on our natural systems, which may be felt for many years to come.

Flooding has a wide range of environmental impacts, including erosion, habitat loss, weed dispersal, and the release of harmful pollutants. Floods can also disrupt the natural functioning of ecosystems such as wetlands.

Moreton Bay receives water from four major rivers in SEQ – the South Pine River, Caboolture River, Logan River and the Brisbane River. During flood events, the amount of water travelling through these systems increases substantially, carrying with it mass amounts of pollution, including sediment, debris, pesticides, heavy metals, and other toxic compounds.

The 2022 floods saw our coastlines inundated with ‘white spill’ – tiny polystyrene beads resulting from the breakup of Brisbane River pontoons from which came adrift during the floods.

A study following the 2011 Queensland floods estimated the discharge from the Brisbane River during the month of January was equivalent to approximately 36% of the volume of Moreton Bay, with over 1,000,000 tonnes of sediment flushed into the bay over the course of the event (data obtained from the Queensland Government Water Monitoring Information Portal).

The mass discharge of water and pollutants during flood events has important consequences for our internationally significant Moreton Bay Ramsar Wetland. Wetlands are particularly vulnerable to pollution due to their proximity to discharge areas and their capacity to capture and concentrate excess sediment, nutrients and pollution.

Under normal conditions, wetlands act as a natural filter, removing nutrients and sediment before releasing water into Moreton Bay or underground aquifers . However, they can only absorb so much, and an oversupply of nutrients, sediment and other contaminants can have significant negative impacts, including smothering aquatic plants and animals, triggering toxic algal blooms, and affecting the health and biodiversity of wetland species.

While it will be some time before we fully understand the scale of environmental damage from the most recent floods, ongoing monitoring will be essential to ensure the health of these sensitive ecosystems and inform future mitigation measures.

You can help reduce marine pollution by:

  • Covering bare soil with plants or mulch.
  • Minimising the use of herbicides and pesticides, especially before rain and around waterways.
  • Putting rubbish in the bin.
  • Picking up after your dog when walking.
  • Not flushing contaminants down the toilet or drain.

The Moreton Bay Ramsar Wetland project is supported by Healthy Land & Water through funding from the Australian Government’s National Landcare Program. 

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