Research informing the estimation of sediment reductions for gully rehabilitation programs

Monitoring the effectiveness of gully rehabilitation is leading to better constrained estimates of the sediment reductions from gully rehabilitation. From water quality and other measurements across a range of treated and untreated gullies, recent research in the Burdekin confirmed that gully baseline sediment yields vary by orders of magnitude. This reinforces the importance of focusing on sites with large yields so that sediment reductions can be delivered efficiently. This research also found that several common gully rehabilitation techniques in use in GBR catchments can all be highly effective, provided that the appropriate technique is selected, that it is designed and installed well. The effect of long-term grazing exclusion on gully sediment yield in the upper Burdekin was quantified at more than 50% reduction in gully sediment yields. Diverting runoff away from gully headcuts was also shown to be effective if water can be either retained or safely delivered to the stream elsewhere. Gully reshaping and revegetation can be highly effective if livestock access is controlled, and surface erosion is controlled in the initial years. Translating site monitoring into effectiveness look-up tables requires accounting for the scale of monitoring (whether all parts of the gully were monitored), the duration of monitoring (short term monitoring results are sensitive to the climate), risk of extreme events, spatial completeness of works across a gully, control of livestock access and ongoing maintenance, independent technical review to validate the appropriateness of effectiveness estimates for sites. Some gaps in system understanding remain, in terms of certain soil types, treatments, climatic conditions and the persistence of outcomes. Research can continue to inform ongoing adaptive management of gully erosion rehabilitation programs by monitoring large erosion control sites.