Southern Gulf NRM is working with land managers to restore riparian areas following the monsoon event of early 2019 which drastically impacted North West Queensland.
During that natural disaster, a torrential amount of rainfall swelled riverbanks and waterways well beyond their capacity. The sheer volume of water pushed vegetation, soil and the banks of the rivers themselves downstream.
In some areas, 100m of riverbank, equivalent to 25,000 cubic metres, was lost, resulting in 8m high cliff faces. Some residents feared the loss of their homes.
Not only is this erosion of banks an issue for landowners, the loss of vegetation means the subsequent loss of vital habitat for many local species of flora and fauna.
As soon as flood waters receded, Southern Gulf NRM was on the ground helping landowners and local councils to assess the damage. They called for expressions of interest to identify high-priority areas of erosion with 28 submissions received.
Engineering firm Neilly Engineering Group undertook assessments and five sites were prioritised for funding using a set of three criteria – cost of site remediation per tonne of fine sediment export to the coast; presence of infrastructure at risk from further erosion; and the likelihood of ongoing erosion.
Two sites on the Flinders River and one each at Alick Creek, Cloncurry River and Dutton River were identified as priority locations.
Alick Creek is a tributary of the Flinders River, which was inundated during the 2019 Monsoon Trough. While the nearest BoM streamflow gauge was 47km north-est of the site, previous data show that the highest streamflow records are just 10 – 20 per cent of those experienced during this monsoon event.
Comparison imagery from 2013 to 2019 indicated the riverbank had retreated approximately 9 metres, most likely due to the rainfall received during the event. The estimated soil loss was 30,150 tonnes.
After visiting the site, Neilly Group Engineer and Southern Gulf NRM staff recommended bank battering of eroded sections; installation of irrigation at suitable sites; and revegetation with grass, hydromulch and suitable trees and shrubs on the reprofiled bank batters and adjacent floodplains.
The cost of these remediation works – which were all completed in March 2022 – was $668,000.
Southern Gulf NRM’s Project Officers developed a monitoring program using the Biodiversity Condition Assessment Tool (BioCAT) and monitoring will continue until June 2024 to evaluate the outcomes from this project – and the four others funded through the program.
The Alick Creek landholder has already noted the success of the works.
“The DRFA works project on Alick Creek at this stage is successfully stabilising the banks and producing a positive landcare outcome for the area,” they said.
As part of ongoing evaluation, monitoring sites have been established. It is expected the following outcomes will be achieved:
- prevention of the ongoing export of fine sediment to the Gulf of Carpentaria from future erosion
- protection of productive grazing land from further loss through erosion to stop existing erosion
- restoration of riparian vegetation connectivity that was lost due to the erosion.
This project was delivered by Southern Gulf NRM and jointly funded by the Commonwealth and Queensland Governments under the Disaster Recovery Funding Arrangements (DRFA).