Erosion from alluvial gullies is a major source of sediment impact onto the Great Barrier Reef lagoon. Mitigating this erosion is therefore a key technique in improving water quality in Australia’s tropical marine ecosystems.
In late July the world’s experts on erosion, including two research teams from the NESP Tropical Water Quality Hub, met in Townsville for the 8th International Gully Erosion Symposium, the first time the event had been held in the Southern Hemisphere.
TWQ Hub was also a Silver Sponsor of the event, and the event culminated in field trips to a number of gully management sites run by Hub researchers.
Assoc Prof Brooks and Griffith University’s Precision Erosion and Sediment Management Research Group presented five talks and six information posters at the Symposium, sourced mostly from the five NESP gully erosion science projects led by Assoc Prof Brooks over the last four years.
Assoc Prof Brooks said the presentations were ‘very well received and shown to be at the cutting edge of the science at an international level.’
“A key aspect of our research is that it is highlighting that by tacking the large alluvial gully systems, that significant inroads can be made towards reducing sediment loads over a very short period of time if the effort is appropriately targeted,” he said.
“The gully mapping and classification work is showing us exactly where that effort needs to be targeted to achieve the GBR water quality targets.
“We still have a long way to go – but through the efforts of this research we now know that the targets can be achieved and what we have to do where to achieve them. All that’s needed now is the appropriate investment.”
Dr Bartley spoke on her project, involving the trialing of different erosion mitigation techniques in the Burdekin River Basin.
These techniques include fencing, stock exclusion, sediment trapping structures and hillslope vegetation management.
Effectiveness is being monitored in several ways at each test gully and its non-remediated control counterpart, including vegetation cover, biodiversity, repeated 3D laser scans to monitor soil volume and detailed water quality measurements. Dr Bartley’s research has also contributed to understanding the role of colloidally-suspended nitrogen in runoff from grazing and sugarcane land, with major implications for Great Barrier Reef water quality management.
Dr Bartley said the Symposium was an excellent opportunity to access the global ‘brains trust’ on erosion, highlighting the importance of erosion control in economic as well as environmental contexts across the world.
“It was great meeting and talking to people with a lot of experience on gullies,” she said.
“There is a band of semi-arid systems stretching around the world that are dealing with these same issues in erosion including Spain, India, Africa, here in northern Australia and also in the USA, specifically Arizona.
“In India they are trying to fill gullies in for more growing land, in China they are trying to minimize land loss. In Africa the concern is mainly about sediment in the drinking water. Gullies can also destabilize infrastructure like bridges and roads. The US and Spain have similar issues to us in that they are also trying to minimize that danger to infrastructure and also improve their water quality.”