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Sections of the Williams River and Stockyard Creek (near Wollombi) are being rehabilitated using a technique designed to re-introduce large woody debris (logs) into waterways. The research project, involving Macquarie University, is trialling methods of stabilising rivers by anchoring large logs into streambeds and streambanks.
The project is the first of its type in Australia and uses methods developed in America and Canada that have been adapted to suit Australian river conditions.
Both the Williams River and Stockyard Creek have suffered a range of human-induced disturbances including riparian vegetation clearance, de-snagging and removal of riffles, loss of vegetation from riverbeds, and channel realignment. These disturbances have caused riverbank and riverbed instability, however the sites were chosen for the trials as they showed potential to regenerate after the large woody debris was installed.
The Williams River gravel bed trials were installed in September 2000 with more than 400 logs being placed in a 200 metre section of the river. The Stockyard Creek sand bed trials, completed in May 2002, comprise of 550 logs in 23 structures over a 1.2 kilometre length of the stream. At both sites native riparian vegetation has been planted to assist with stabilisation of the riverbanks. Australian bass and silver perch are just two of the species of native fish benefiting from the increased diversity in aquatic habitats. Results to date indicate that the number of fish species at the project site have increased by 50% compared with an increase of only 30% at a control site.
1. Now Hunter-Central Rivers Catchment Management Authority For more information please contact us. Relevant links:The Upper Hunter River Rehabilitation Initiative
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The engineered log jams replicate natural conditions by creating pools and
riffles that are essential for healthy rivers. Pools provide areas that are deep
enough for fish to live and breed in and riffles help prevent stagnation and
layering of water, factors which encourage the growth of toxic blue-green algae.
The
long-standing river management programs run by the then Hunter Catchment
Management Trust1, NSW Department of Land and Water Conservation2,
and strong community involvement through the Williams River Total Catchment
Management Committee3 and Wollombi Landcare were also key considerations in
choosing the sites.
Grant funding
for the large woody debris initiative was provided by Land and Water Australia. 