cost-effective where they prevent small numbers of large but young gully heads incising large upstream areas ( Heede , 1979b ). This will more likely be the case in management units with large length-specific or area-specific gully contribution ( t / km / y or t / ha / y ). In the context of the ‘ ABCD ’ management practice framework , practice combinations 2 and 3 are akin to ‘ B ’ management practice , or Low Risk in the Paddock to Reef WQ Risk Framework . The cost effectiveness of practice change was calculated for 4 priority management units of Normanby , Bowen-Bogie , Lower Burdekin and Don indicating that the cost of sediment reduction from gullies is around $ 160 per tonne . Large gains in cost effectiveness can be achieved by targeting areas of intense gully erosion within priority management units , where each km of fence isolates the largest possible length and area of gully erosion . Where the efficiency of fencing can be increased to 1 km of fencing for 10 km of gully feature the cost of combination 3 becomes $ 4,500 per km of gully , and the costeffectiveness becomes as low as $ 81 per tonne . However , it is not known what proportion of all gullies can be managed at this fencing efficiency , which should be determined through evaluation and adaptive management .
Table 7 . Effectiveness of selected combinations grazing practice changes to manage erosion of existing gullies . Reproduced from Wilkinson et al . ( 2015a ).
Practice combination
Description
1 Destock the gullied paddock , for occasional dry-season crash-grazing .
2 Fence gullied area , for occasional dry-season crashgrazing , and continuous spelling otherwise . Stocking rate in surrounding area managed within longterm carrying capacity and adequate pasture and groundcover retained at the end of the dry season .
3 As per 2 above , plus stabilisation using gully stick trap or other revegetation .
4 As per 3 above , plus hydroseeding .
5 As per 2 above , plus gully reshaping earthworks or rock drop structures .
Related WQ Risk Framework Performance indicators ( McCosker , 2013 )
Infrastructure cost to transition from C / D practices ( Moderate – High Risk ) ($/ km ) a
1 , 3 , 6 $ 0 10 – 20 %
1 , 2 , 3 , 4 , 6 $ 5,000 per km of fenceb 30 %
6 $ 4,500 – 9,000 per km of gullyc ($ 5,000 + $ 4,000 )
6 $ 4,500 – 9,000 per km as above + $ 10,000 – 30,000 per had
6 Drop structure : $ 30,000 – 50,000 per gully heade Reshaping and seeding : $ 10,000 per gully head
Cumulative sediment reduction changing from C / D practices ( Moderate – High Risk ) a Opportunity costs of de-stocking gullied paddocks are not included here . b Advice from NQ Dry Tropics ( 2014 ). c Range depends on the fencing efficiency ; 1 km fence per km of gully results in a total cost of $ 9,000 per km , being $ 5,000 fencing , and $ 4,000 per km for check dams assuming 30 stick trap check dams per km ( 33 m spacing ), 2 person-hours per structure at $ 50 per person per hour plus materials and grass seed . $ 4,500 equates to 1 km of fence for 10 km of gully , and $ 4,000 for check dams . d Depending on scale of project ( Shellberg and Brooks , 2013 ) e Condamine Alliance , Case study 1 : Allora . Based on gully density of 4 km / km2 and one rock drop structure at $ 30,000 and reshaping of smaller adjacent features at $ 10,000 ( Little , 2014 )
50 %
70 %
70 %
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