Low-impact waterway erosion control also cares for fish
The Belmore Downs gully remediation stage 2 project addressed erosion control, while at the same time ensuring the on-ground work was compliant with Fisheries Act regulations about waterway barriers.
One of the eroding gullies, referred to as gully 3B on the map, pictured, right, was identified as a low-impact (green) waterway.
Gully maintenance and monitoringNeilly Group Engineering designed a rock chute (spillway) to meet the Accepted Development Requirements for that kind of construction on a low-impact waterway.
The work is part of the Gully Maintenance and Monitoring project at NQ Dry Tropics.
The spillway design followed specific criteria:
- A spillway channel integrated into the design on the downstream side of the weir or dam.
- The channel must have a continuous slope without abrupt vertical drops.
- No vertical drop where the spillway meets the natural bed of the waterway.
Geometrical conditions include:
- A maximum grade of 5 per cent (1 in 20 slope).
- A concave shape.
- For a height or drop greater than 3 metres above the waterway bed, the design required:
- 3-metre diameter pools at 20-metre intervals along the channel.
- A minimum pool depth of 300mm below the spillway bed.
The spillway and pools now serve dual purposes. The spillway controls erosion, and the pools facilitate fish migration by creating resting areas, ensuring the upstream passage of fish is not obstructed.
This project is part of the Landholders Driving Change Program funded by the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation.
