 |
 The
Hunter River once contained extensive volumes of large woody debris (LWD) deposited
by its riparian forests. LWD has been removed to speed up flood flows and because
of a perception that it contributes to bank erosion. However, the removal of LWD
has been found to be one of the principle causes of channel instability and, consequently, instream habitat loss and homogenisation.
Recent research has demonstrated that engineered large woody structures (LWS) are able to withstand
flood flows, increase the complexity of channel morphology and the number of
riffle-pool sequences, and increase the volume of sediment stored in the reach.
This means bank stability increases, and the diversity and abundance of fish
species also increase within test reach. The photo shows Dr Andrew
Brooks standing on one such structure located on the Williams River.
The UHRRI will reinstate specially designed LWS along an 8 km section of
the Hunter River, with logs sourced from coal mine operations in the Hunter
Valley. The research will focus a number of issues, including:
- Engineering and hydraulic issues associated with reintroducing LWD into
a mobile gravel-bed river system
- The potential for using large wood to reintroduce geomorphic complexity
into a large, highly disturbed river
- The relationship between habitat complexity and aquatic ecosystem functioning
- The relationship between wood obstructions and hyporheic zone (subsurface)
nutrient exchange
- The importance of wood substrate as a limiting factor in food web dynamics
- Species level relationships between fish, macroinvertebrates and woody habitat
- The relationship between physical habitat improvements, European carp and
native fish
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