The 1950s marked a turning point in the history of the Hunter River. In between the catastrophic floods of 1949 and 1955, the Hunter Valley Conservation Trust was formed and in 1956 the Hunter Valley Flood Mitigation Act was established.
Government investment in river rehabilitation took off around this time and a program of capital works was identified to stabilise degraded sites along the river. During this time various river erosion control techniques were being pioneered and tested.
One of these techniques included planting willow trees to help stabilise the riverbanks. This proved to be effective but led to many other unforseen environmental problems.
In the 1990s government authorities responsible for the management of rivers in the region had a policy of clearing trees from streams in order to allow the water to flow freely in the channel. The benefit of improved science and a greater understanding of riparian processes led to a change in this practice, and today the benefits for the natural regeneration of streams of allowing trees and debris to remain in the channel are well documented.
At this time the exotic willows that had been planted in previous decades were being removed and replaced with native vegetation due to the impacts they had begun to have on the natural ecosystem, including choking the stream with large volumes of leaf matter and out-competing native species.
Increasing community interest in river management and the beginnings of a Rivercare Program in NSW, led to the development and implementation of Rivercare plans to target local issues, with support from government agencies and organisations like the former Hunter Catchment Management Trust.
Today the approach towards river rehabilitation has evolved to include basic stabilisation of sections of the river and enhancing the natural recovery of streams. Through the CMA's riparian incentives program, private landholders can apply for funding from the Catchment Management Authority (CMA) and other government agencies to carry out work to stabilise and enhance riparian vegetation on their river frontage. Activities generally funded include fencing off riverbanks, and establishing off-stream watering points for stock, tree planting, and weed control.
Just south of Muswellbrook is the site where an important research project into river rehabilitation called the Upper Hunter River Rehabilitation Initiative (UHRRI) was undertaken. The UHRRI project was undertaken on a 10 km reach of the Hunter River south of Muswellbrook, and was designed to trial and research various methods of river rehabilitation in the Hunter.
The main aims of the five-year project, which was completed in 2007, were to research the effects on the river over time of: installing log structures along the edges of the stream, which are designed to trap sediment and reinforce vulnerable sections of riverbank; and planting a variety of native plant species along the riverbanks to help naturalise areas that had become overgrown by exotic weed species, including willows.
The project was funded by a five-year grant from the Australian Research Council as well as contributions from a range of government agencies and corporations, including the NSW Department of Natural Resources, NSW Department of Primary Industries, the Hunter-Central Rivers CMA, NSW Department of Lands, Newcastle Ports Corporation, Mt Arthur Coal, Bengalla Mining Company and Macquarie Generation.
The research was undertaken by scientists and postgraduate students from Macquarie University, Griffith University, the University of New England and NSW Fisheries.
The research conducted through the UHRRI project highlighted some of the changes that had occurred in the streams of the Upper Hunter since the 1820s. The more sensitive streams had changed substantially, with channel widths increasing by four or five times since European settlement; while other sections of stream channel had changed very little in that time.
Over 60 000 trees and shrubs were planted on the 80 ha UHRRI project site. Prior to the project, there was a very low diversity of native species on the project site. Despite losses incurred due to drought the revegetation of the site with native species will lead to significant and lasting improvements to riparian health over the longer-term in a severely degraded section of the upper Hunter River (from final ARC report).
Up to four Green Corps teams of 17-20 year olds participated in aspects of the project, including through National Tree Day, School Planting Days and other activities.
Some setbacks with lost plants during the drought led to the development of planting guidelines on site preparation, planting methods, maintenance, and plant selection, to help improve the survival rates of young plants in drought conditions.
One innovative technique that proved to be successful was planting native species amongst existing exotic vegetation. This gives the young seedlings some protection while they get established, while over time, contributing to a transition from a weed-dominated environment to one dominated by native species.
Through the project 32 engineered log structures were installed over the 10 km of channel length in the study reach. These structures were found to be effective at mitigating bank erosion and they also provided important instream habitat for fish and invertebrates. Fish were actually found to prefer the special 'fish hotels' that were built for them to the habitat found along the riverbanks (from final ARC report).