WRC drains | Landholders Driving Change

Carlos Barrero (left) and Scott Hardy from Whitsunday Regional Council and NQ Dry Tropics project officer Dan Hazelman (centre).

Determining how best to manage runoff on rural roads

Rural roads in the BBB directly serve thousands of rural and regional residents living along them. They provide essential market access for grazing properties, are the main access for major industries, and they play a major part in tourism, adding to the economic wealth of the region.

Roads are unnatural structures in the natural environment, and are susceptible to erosion because they collect runoff from overland flow, as well as from rain falling on the road surface. 

Good road drainage and maintenance is the best way to combat water’s damaging influence – keeping water off, out of, and away from the road. 

The challenge rests in simultaneously preserving our roads and environment in a safe and cost-effective manner.

Whitsunday Regional Council Natural Resource Management Coordinator Scott Hardy

That’s why LDC has approached Whitsunday Regional Council (WRC) to work on a collaborative project to monitor the sediment difference between V bottom and flat bottom drains in the BBB catchment. 

The aim is to test the assumption that flat bottom drains provide water quality benefits, and lower maintenance costs.

With input from landholders and WRC council maintenance crew, several potential sites have been selected, a total of six drains to be monitored including three treatment and three control sites. 

Fruition Environmental has supplied the monitoring methodology, it includes:

  • Soil tests conducted at each site to obtain data about site factors that influence erosion.
  • Drone survey done to allow a DEM (Digital Elevation Model) of difference to be produced to quantify erosion volume at each site over the wet season. It will also allow cross-sections to be derived to estimate discharge at the sample location, and to get basic information relevant to the USLE (Universal Soil Loss Equation) equation.
  • Photo reference points collected to allow repeat monitoring photos.
  • Two rising stage samplers installed at each site. The intention is to take up to three sample collections during the wet season to be analysed for sediment sample concentration and particle size distribution. This will show what concentration and particle size is moving during rainfall events. TropWATER will analyse the water samples. Fruition Environmental will collate and report the findings.

The LDC project and WRC are in discussions on how best to progress this important project.

Erosion is a problem for everybody

Erosion isn’t just an issue for graziers. The LDC project aims to involve all land managers in the BBB, including mines, utilities and government departments.

Getting the whole community working together and learning from each other will help achieve better long-term land management and improved water quality in the BBB.

That is why the project has an activity area called ‘Influencing Other Land Managers’. This activity area encourages non-graziers who manage or use land in the BBB to get involved with the project so it can truly be a whole-of-catchment effort.

Although 92 per cent of the land in the BBB is used for grazing, other areas include national parks, state forests and coal mines. Four local councils operate in the catchment, which also features major infrastructure such as power transmission lines, rail lines and local and main roads.

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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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