Assessment of Riparian Revegetation Trials on In-Channel Benches in the Hunter Valley of Southeast Australia

Large-scale river training works have been carried out in the Hunter valley since 1955 in response to flood-driven channel changes. Vegetation was planted on in-channel benches induced by river training works to consolidate the deposits and to increase channel boundary roughness. Exotic species of vegetation such as willows and poplars were previously used. In 1983, ten trial sites were planted with various species of native vegetation. Survival rates were evaluated in 1987 and 1997. The most successful species planted was Eucalyptus camaldulensis with an overall survival rate of 77 per cent in 1997. The Acacia species were found to be short-lived, exhibiting a significant decline in survival rates between 1987 and 1997. Survival rates for most species were higher on sand-bed than on gravel-bed sites. This difference may be attributed to better drainage on benches at the sand-bed sites. Investigations of flood disturbance showed that between 1983 and 1997 the sites were flooded between four and 13 times. The survival rates of Grevillea robusta and Eucalyptus melliodora trees were negatively correlated with the total number of recorded floods at each site. Poor natural regeneration of planted species is attributed to a combination of periodic flooding, intensive weed growth, low light intensities at ground level and grazing disturbance. These trials were not well designed for statistical analysis but provide valuable long-term information on the suitability of various species for planting in riparian rehabilitation programs. Such information is of relevance not only to river and catchment management authorities, but also to community groups.