Gully work begins | Landholders Driving Change

Griffith University Associate Professor Andrew Brooks, left, is helping the LDC team assess and select priority sites for rehabilitation works.  He is pictured with landholder Christian Cormack, of Glen Bowen.

Gully assessment to be complete this month

THANKS to the landholders who nominated potential gully remediation works. It was great to receive a high level of interest and it is expected all nominated gullies will be assessed and prioritised by the end of this month.
This process started last week with leading gully expert working on the LDC project, Griffith University Associate Professor Andrew Brooks, visiting several properties accompanied by LDC Project Manager Andrew Yates and field officers.
The aim is to develop fast, effective and economical approaches to gully remediation, drawing upon the knowledge of graziers and technical specialists.
Although all 17 sites cannot be remediated under the LDC due to funding and time constraints, the LDC intends to produce a high resolution spatial map of these active gullies, and where possible eroding stream banks, to develop a rehabilitation investment prioritisation for the BBB beyond the life of the LDC.
This means there will be multiple shovel-ready projects available to take advantage of future funding opportunities.

ON-GROUND WORKS OPPORTUNITIES

BBB landholders also have a suite of funded on-ground works available to them as part of the Landholders Driving Change project to help them reduce sediment in the water flowing into the Great Barrier Reef lagoon.
Here are some of the options available:

  • Diversion banks and water spreading structures – to control water flow across paddocks and manage water flow at, before, or after, erosion features i.e. grassed or ungrassed diversion banks.
  • Sediment traps / Silt traps – to slow water flow and collect sediment from erosion features.
  • Direct on ground rehabilitation – earthworks, grade control, soil stabilisation, revegetation.
  • Within gully management structures such as rock chutes, rock armouring, use of mulching products, spray-on batters, bio-layering, gully reshaping.

Landholder Christian Cormack (front) leads Griffith University Associate Professor Andrew Brooks and NQ Dry Tropics LDC team members Brendan Smith and Andrew Yates into a gully that will be assessed by the LDC team for possible rehabilitation.

  • Road and farm trail works – construction of cross banks (whoa boys), rehabilitation or re-siting roads.
  • Contour ripping – to enhance pasture and soil water holding ability.
  • Re-seeding of pasture – to improve productivity of pastures, repair degraded areas, or repair preferentially-grazed areas (i.e. can also require fencing or ripping).
  • Water distribution infrastructure and water points – to control grazing pressure and enable grazing land management change.
  • Off-stream water points – to manage grazing pressure off natural water features.
  • Permanent paddock fencing – to manage pastures or specific erosion features.
  • Permanent riparian fencing – to promote protection of high value wetland and waterway areas.
  • Temporary fencing – with, or without, cattle exclusion to improve land condition.

Contact the LDC team to discuss a tailored solution for your property.

Click here to read Andrew Brooks comments about how unstable soils in some areas of the Bowen, Broken, Bogie (BBB) catchment are especially prone to erosion. Andrew Brooks media release 10.05.17

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Figure 1. Total fine sediment reduction by project type and erosion source. Inset shows the proportion of the total project area for each project type.

These estimates have been calculated using two methods: 

1) The pollutant reduction component of the Alluvium/Great Barrier Reef Foundation (GBRF) investment tool for hillslope and streambank erosion management projects; 

2) The Reef Trust Gully Toolbox method for gully erosion management projects. The LDC Water Quality Report 2020 (Waterhouse et al., 2020) highlights that a number of assumptions underlay these calculations, therefore these figures should be treated as the best available estimate of sediment reductions to date.

Preventing sediment from reaching the Great Barrier Reef

Each wet season sediment is washed into local waterways and out to the Great Barrier Reef (GBR). 

Most sediment is very fine, and can stay suspended for a long time and can travel great distances. Valuable topsoil is lost from production, and increased concentrations on the reef can be harmful to seagrasses and corals. 

Landholders in the BBB have completed 69 on-ground water quality practice changes, and it is estimated that these have contributed a fine sediment reduction of 6,154 tonnes per year from reaching the GBR. 

Of this, approximately half of the sediment savings are attributable to grazing land management changes on hillslopes and streambanks, and the other half as a result of gully remediation treatments across a broad range of scales, as shown in the graphs above. 

The table below also highlights the relatively small area of intervention in the gully management projects compared to the large sediment savings that these can achieve - 60 per cent of the sediment savings over only 4 per cent of the project area.

Table 1. Estimated sediment reductions (tonnes) from projects completed in the LDC Project to date.

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*GLMWW = Grazing Land Management Wire and Water

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*The Exploring New Incentives activity area has provided an opportunity for graziers to adopt improved land management practices through a range of activities. For some of these properties, it was the first time they signed contracts for on-ground works.

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The LDC project monitors four gully sites (represented in this table) with gold standard equipment and analysis, carried out by CSIRO.

Results have been compiled in a preliminary report from Bartley et al (2020), with the final report expected to be released by the end of 2020. The preliminary report shows all four sites have indicators of improvements, notably the Strathbogie and Mt Wickham sites.

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Reef regulations - grazing, standard conditions

  1. For land in good or fair condition (more than 50 per cent ground cover at 30 September), continue using measures to maintain land condition.
  2. For land in poor condition (less than 50 per cent ground cover at 30 September), steps must be taken to improve land condition.
  3. For land in degraded condition (less than 20 per cent ground cover at 30 September), steps must be taken to improve land condition OR prevent areas from further degrading or expanding.
  4. Keep records of measures taken and also of agricultural chemicals, fertiliser and mill mud or mill ash applied to land.
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