Image: TRaCK CERF
Scientists in Queensland have used remote sensing technologies to analyse erosion in the Mitchell River catchment.
The researchers used landsat analysis and 3D lidar data to find that the main river channel can shift up to 100 metres sideways, whilst individual pools several kilometres long can be completely filled up with sediment in a single wet season.
Tropical Rivers and Coastal Knowledge (TRaCK) researcher Dr Andrew Brooks from Griffith University said that the river was extraordinarily powerful.
Researchers found that despite river channel changes in the past few decades, there appeared to be no significant increase in sediments. But the story appears to be different when looking at 100 years or more.
“We found that most of the erosion into rivers comes from alluvial gullies, or 'breakaways' as they are known locally, that have developed over the last 130 years on the floodplains adjacent to the main river channels,” said Dr Brooks.
The modelling of the sediment in the Mitchell shows that erosion appears to have doubled since European settlement, largely due to the increased erosion from these alluvial gullies.
Such gullies cover less than 0.5 per cent of the landscape, but they generate two thirds of the river’s sediment load.
TRaCK researchers are not yet sure of the full implications of their findings, but last week met water and land managers in the northern Gulf to discuss their results.
Other TRaCK researchers will be discussing how river landscapes can be classified for better management, the effects of floods on the Norman River estuary, and findings about the natural food webs in the Mitchell and Flinders Rivers.
“All of our research is about providing knowledge to help managers and users of northern rivers to make the best possible decisions about any river development or conservation actions,” says Ruth O’Connor, TRaCK knowledge and adoption coordinator.