Gully field days show landholders
what’s involved in remediation

Department of Agriculture and Forestry Principal Extension Officer Bob Shepherd explains some of the principles of gully remediation.

Griffith University Associate Professor Andrew Brooks.

LDC has hosted field days at the Havilah and Gattonvale large-scale gully remediation site to bring landholders in at the beginning so they can see firsthand what is involved in remediating a gully.

NQ Dry Tropics hosted two field days on LDC’s large-scale gully remediation project on Havilah and Gattonvale stations before ground was broken.

NQ Dry Tropics Land Remediation Officer Dan Hazelman (pictured) said the idea was to hold three field days — Before and After the Wet, and After Remediation — for graziers to hear from engineers and civil contractors and get an appreciation for what’s involved in gully remediation from start to finish, as well as maintenance.

Topics covered included:

  • identifying and discussing erosion activities and processes that occur in a gully;
  • inspecting and identifying soil layers with basic slaking/dispersion testing;
  • discussing the remediation techniques proposed at the site, their purpose and influence of the erosion process in the future; and
  • establishing monitoring techniques by establishing markers points of ground level, head cuts and other key points to re-inspect following the wet season.

Dr Andrew Brooks, from Griffith University, and Bob Shepherd and Simon Hunt from Department of Agriculture and Fisheries were guest speakers at the most recent field day.

Andrew Brooks talked about erosion activities and processes that have occurred in the gully and participants walked the gully to inspect the different processes. They also identified how those processes changed during the wet season based on marker points established during the first field day held in December last year.

Remediation techniques carried out at the site were also discussed, including their purpose and influence of the erosion process in the future.

Bob Shepherd and Simon Hunt discussed grazing land management practices that can be implemented post works, and how those practices can be managed long-term.

A third field day will be held post works. A date is yet to be confirmed.

 

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.
KEQ #8

KEQ #7
KEQ #6

KEQ #5

KEQ #4

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.

KEQ #3

*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.

KEQ #1

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.

KEQ #2

*GLMWW = Grazing Land Management Wire and Water

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