Carter site streambank stabilisation

(not documented)

GWT Earthmoving

Conservation

On-ground work

(none)

Australian Government National Landcare Program

$350,395

(not documented)

29 April 2019

21 June 2019

The site is located approximately 1.7 km upstream from the Eumundi-Kenilworth Road crossing. The downstream section of the site consists of a near-vertical bank, approximately 9 m in height. Each of the sections are approximately 120 m in length and are devoid of vegetation. The site abuts a floodplain that sits approximately 3 – 5 m above the inset floodplain immediately upstream of the site.
Streambank erosion at the site has resulted in a high, vertical and unstable bank at the downstream end and a high, steep/irregular bank upstream end. Channel widening and straightening processes have resulted in major sediment mobilisation (approximately 280,000 m^3 between 2013-2019) and over 130 m of bank retreat and subsequent loss of agricultural land. The current steep/vertical bank morphology will likely limit future vegetation establishment.

In the absence of management interventions, ongoing erosion at the site may result in a range of impacts, including:

• Water quality – Increased suspended sediment and nutrient levels will adversely impact on water supplies (including at the Kenilworth town supply offtake downstream), the Great Barrier Reef Marine Park, the Great Sandy Strait and instream river health values.
• Environmental values – Ongoing degradation of the Mary River, including the riparian vegetation zone, which may limit physical habitat of the Mary River Cod, Lungfish, Mary River Turtle and significant frog species including the Giant Barred Frog.
• Agricultural land and electricity infrastructure.

The recommended works for the Carter site include:

• Reprofiling the bank to a gradient of 1V:3H (vertical distance:horizontal distance) which can allow the establishment of native vegetation.
• Installation of rock revetment at the upstream end of the works.
• Installation of pile fields at the toe of bank.

These works will provide immediate protection against erosion and help support the establishment of riparian vegetation.

(not documented)

(none)