LDC Reports MIP16 Report Vol V Bowen Basin Baseline Synthesis Report | Page 29

Table 3 . Total suspended sediment ( TSS ) concentrations ( mg L-1 ) and average ( mean ± standard deviation , SD ) sediment particle size for tributary monitoring sites located across the BBB ( modified from Bainbridge et al . 2016 ). Suspended sediment samples collected over rising and peak stages of the flood hydrograph . Refer to Figure 31 for sampling locations .

Site

Subcatchment

Catchment Area ( km ² )

Wet seasons data collected

Broken R headwaters ( d / s Eungella )

Bowen R ( d / s Little Bowen- Broken junction )

Bowen R ( Myuna gauge )

Lower Bogie ( Kirknie )

Burdekin Falls Dam – overflow

Burdekin River ( Inkerman )

End-ofriver

129,600 2006 / 07- 2010 / 11

Mean TSS ( mg L ^-1 )

Sediment particle size * ( TSS weighted ) ( mean ± 1SD ) n

< 10 µ m fraction (%)

Clay (%)

Fine silt (%)

Coarse (%)

1055 6 73 ± 16 36 ± 11 49 ± 4 15 ± 13

2880 110 63a 27a 49a 24a

305 3 43 ± 7 15 ± 4 43 ± 2 42 ± 7

510 15 61 ± 16 31 ± 16 48 ± 9 21 ± 13

180 50 86 ^a 52 ^a 41a 6a

475 34 71 ^a 37 ^a 44 ^a 19 ^a

* Size fractions : clay (< 3.9 µ m ); fine silt ( very fine and fine silt 3.9-15.6 µ m ); coarse ( coarse silt and sand 15.6-2000 µ m ) a

From Bainbridge et al . 2014 , 2016 loads based sediment budgets , using 2005 / 06 to 2008 / 09 PSA data only .

4.2.2 Soil erosion A soil erodibility map and dataset for the whole of the Burdekin basin has now been developed ( Zund and Payne , 2014 ) showing how vulnerable a soil is to erosion . The map splits soils into 17 categories in 90 metre pixels based on soil attributes that are key drivers of soil erodibility ( e . g . soil texture , soil sodicity , salinity and cation balance ). The overall inherent soil vulnerability layer ( Figure 16 ) shows that the most extensive areas of highest soil erodibility are located above the Burdekin Dam in the Suttor , Belyando and Cape Campaspe catchments , with smaller but also intensive areas of high overall soil erodibility in the Upper Burdekin and BBB catchments . The larger scale map of the BBB catchment ( Figure 17 ) highlights areas of high soil erodibility in the Bogie River , Pelican Creek , Bowen River , Glenmore Creek and Rosella Creek sub catchments .

This map is useful for refining target areas for intervention and prevention measures aimed at reducing all forms of erosion including gully erosion . However , the data should be combined with other available information and knowledge such as slope , land use , climate data and land cover data to fully assess risk of soil erosion occurring . For example , areas with a high vulnerability to erosion are unlikely to be eroded if they have low grazing pressures and consistently high ground cover , whereas areas of low vulnerability can still erode under sufficient grazing pressure . Inherent vulnerability to erosion does not equal erosion outcome necessarily ( Zund and Payne , 2014 ).

- 29 -