Effects of re-introduction of large woody debris into the Little Yarra River, Victoria

In the early 1990s large woody debris (snags) were removed from a 1.5 km reach of the Little Yarra River, a rural tributary of the Yarra River, about 60 km east of Melbourne.  Until recently, de-snagging was a common practice aiming to reduce over-floodplain flows in many Australian rivers.  With increased awareness of the importance of large woody debris as habitat for in-stream fauna, the practice has become rarer, and many agencies are actively 're-snagging' rivers.  The Little Yarra River presented an opportunity for a re-snagging experiment for Melbourne Water Corporation, as the bulk of the removed snags were left on the floodplain in the intervening years.  In January 2002, the snags were re-introduced into the stream.

Being predominantly a sandy substratum stream, reintroduction of large woody debris is anticipated to be important for increasing the availability of both stable and more diverse habitat.  Theoretically these changes should result in an improvement in ecosystem condition.

The re-introduction presented an opportunity for two student projects to assess changes to the stream.  Rhys Coleman (MSc candidate, Biological Sciences, Monash University) conducting an  integrated assessment of several physical and biological aspects of the whole stream (aquatic macroinvertebrates, fish and platypus) before and after large woody debris  reintroduction to determine the ecological response to the rehabilitation works.  Nicole McCasker (BSc (Hons) candidate, Biological Sciences, Monash University) is studying succession of macroinvertebrate assemblages colonizing the re-introduced wood and comparing changes to the composition of assemblages on wood that was already in the stream prior to re-introduction.

For more information contact:

Rhys Coleman
Melbourne Water Corporation
East Melbourne

and

CRC for Freshwater Ecology
Water Studies Centre,
Monash University
PO Box 23 Clayton Vic. 3800, Australia