curve , 64 % of the sediment yield is derived from alluvial gullies ( or potentially higher as the yield of large alluvial gullies was underestimated in the model ). The estimates showed that :
• 1 % of all gullies (~ 260 gullies ) contributed 10 % of the total fine sediment yield .
• 2 % (~ 460 gullies ) contributed 15 % of the total fine sediment yield .
• 6 % of all gullies contributed 30 % of the total fine sediment yield .
• Gully clusters ( i . e ., groups of gullies with their outer margins < 10m apart ) contributed ~ 390 kt / yr of fine sediment from just 200 ( or 2 %) of all clusters . An alternative kernel density clustering approach similarly indicated that 200 kt / yr of fine sediment was delivered from just 73 clusters .
Targeting these high yielding gullies or gully clusters provides the means to achieve the greatest water quality improvements in the shortest possible time . The five sites that were identified for detailed site scale analysis through the preliminary prioritisation ( section 5.1.1 ) at the project outset are all within the top 73 clusters .
Figure 38 : Fine sediment yield curve depicts a small number of high yielding gullies contributing 30 % of the catchment fine sediment yield ( yellow bar ).
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