To analyse remediation and maintenance costs, the small-scale sites were again separated into the two groups( catchment and gully treated and catchment only treated). The sediment saving estimate for projects varied considerably, ranging from 1-138 t / y at the site( Table 4). Like the largescale projects these estimates lack certainty. The variation in sediment savings has a large influence over the cost effectiveness for each site. Table 5 presents average cost effectiveness metrics. The two small-scale sites that failed to stabilise, Sites
19 and 22, are not included in Table 5. The median cost effectiveness for the two groups, small-scale catchments and gullies and small-scale catchments only, are $ 1560 / t and $ 2522 / t respectively. Maintenance at the eight small-scale sites was relatively expensive compared to the initial costs; maintenance at 50 per cent of the initial implementation costs was not uncommon. There were no maintenance funds spent on catchment only sites.
Table 5. Summary of the cost effectiveness of the 24 sites *.
Cost effectiveness statistics ** Mean($/ t) Range($/ t) Median($/ t)
Number of samples( n)
Large scale $ 607 $ 420- $ 570 $ 573 4 Small- gully + catchment $ 2,309 $ 6,322- $ 548 $ 1,561 13 Small- catchment only $ 2,408 $ 3,750- $ 1230 $ 2,522 4
* Caveats: 1. There is considerable uncertainty around the sediment saving estimates( t) for all sites. 2. Sample numbers are small. ** Outlier sites not included: 5, 19, 22.
NQ DRY TROPICS 39