Maintenance program to ensure riverine repair work remains effective
A two-year program to shore up the effectiveness of riverine landscape repairs after Cyclone Debbie in 2017 and the Monsoon Trough event in 2019 aims to upskill land managers and other stakeholders to maintain repair work in the future.
The Riverine Site Maintenance Program, overseen by NQ Dry Tropics’ Soil Conservation Officer Bernie Claussen focuses on six sites repaired under the Disaster Recovery Funding Arrangements at Don River, Gainsford Station, Major Creek, Miles Lake, Molongle Creek and Two Mile Creek.
Two of the sites are working well and need no immediate attention, three sites require some weed removal and one site needs additional in-fill, planting and watering to support the establishment of vegetation.
The Disaster Recovery Funding Arrangements: Efficiencies to Resilience Funding Program – Riverine Site Maintenance Program is administered by the Department of Environment, Science and Innovation on behalf of the Queensland Reconstruction Authority.
The sites
DON RIVER, BOWEN
Cyclone Debbie flood repairs holding up
A 600m stretch of bank on the Don River was badly damaged with large erosion scours after the flood breakouts that followed Tropical Cyclone Debbie in 2017.
Remediation, including bank reshaping with a clay and gravel core, rock armoring and top dressing. The remediation works were managed by the Don River Improvement Trust (DRIT).
Latest site assessment (2024):
There are sand deposits on the rock wall which indicate that subsequent wet seasons have tested the structure.
The bank revetment is intact and there are no signs of failure. According to local members of the DRIT, the central part of the revetment at the bend is the section to keep an eye on. It is where water is expected to overtop during a major flood.
Non-natives, Leucaena trees and Giant reed grass (Arundo donax) are well established on the rock wall.
These two species dominate the sandy banks of the Don River in this lower reach of the river.
Native trees (Eucalyptus sp mainly Moreton Bay) are establishing directly upstream of the site however not on the site directly.
The lower part of the bank revetment has been burnt recently and the Giant reed grass has rapidly reshot from its rhizomes.
This suggests fire is not an effective control measure for this introduced species.
GAINSFORD STATION, CHARTERS TOWERS
Hole in the Great Basalt Wall mended
A section of the Great Basalt Wall holding on one side of it, Lake Eumara, an extensive ecologically-sensitive wetlands area was damaged during the 2019 monsoon event.
Flooding blew a hole in the basalt wall which immediately threatened a stretch of the Lynd Highway and in the coming decade could possibly drain the lake and surrounding wetlands.
The site on Allingham Creek, just before it becomes Fletcher Creek was remediated in 2021.
Remediation works included a rock chute with an elevated crest, bund walls, landform reshaping, bank battering and minor revegetation.
According to the most recent monitoring, the repair work is performing well:
The site is in a stable condition. There are no signs of failure from the bunds or rock chute and the chute appears to have had water flowing down it at least once since it was built in 2021.
A variety of native woody tree species including eucalyptus and figs are established along the channel downstream of the rock chute that was disturbed during construction. This vegetation should assist in stabilizing the waterway.
The old gully head cuts further downslope will be monitored for active progression upslope as part of this project.
MILES LAKE, HILLGROVE STATION
Vegetation protects five sites
Five sites threatening the integrity of wetlands around Miles Lake, on Hillgrove Station, 115 km north of Charters Towers were remediated in 2021.
During the 2019 severe monsoon trough, gullies advanced towards the lake at an alarming rate that soil conservation experts judged posed a high risk to the wetlands dependent on the lake.
Works across the five sites included rock chutes, bunds and reshaping. Follow-up repairs were effected in June 2022 to the reshaped land which was deeply rilled after the first wet season.
The latest site assessment is positive and indicates the work has done its job so far.
Ground cover was generally high across the sites, dominated by legume and grass species. Feral pig movement throughout the area is beginning to form compacted pads. These may later develop into pathways for runoff and restart erosion.
There is no evidence the two rock chutes has been engaged. Whilst the bunds and rock chutes are intact, there is a lot of bare ground and the chute abutments have significant rilling and gullies forming. These areas need attention to protect the structures.
The landform reshaping work is intact.
There are minor channels forming in the lower lower sections of the two reshaped sites. Currently, these channels which are draining the whole site are less than 0.5m deep and are discontinuous.
These reshaped sites are dominated by mature Progrades desmanthus plants more than 2m tall.
Buffel grass is present in the higher areas where the progrades is not as thick.
Management of the Progrades is recommended and will form part of the maintenance plan.
