Restoring habitat structure in a sand slug
In north central Victoria near the town of Euroa , the lowland reaches of the local creeks are bereft of habitat for fish and invertebrates as the channels have been filled with immense amounts of shifting sand, collectively called sand slugs. The sand slugs are a result of episodic erosion from the hills of the Strathbogie Ranges, which were extensively cleared and grazed in the late 19th century.
Starting in 1997 the Cooperative Research Centre (CRC) for Freshwater Ecology at Monash University commissioned a study of the geomorphology of the creeks and the sand slugs, and initiated pre-restoration studies of the fish and the invertebrates. The project was designed as a long-term experiment to evaluate the effectiveness of adding structures to the sand-slugged creek sections to provide habitat.
In 2001 with the assistance of the Goulburn-Broken Catchment Management Authority and the CRC for Catchment Hydrology, timber structures made from river red gum railway sleepers (ties) were installed in two creeks, Castle Creek and Creightons Creek. The structures were designed to generate scour pools, and this they did though not as well as originally planned. The initial response to the structures by the native fish was positive. However, from 2002 to 2005 the region was locked in a severe drought that greatly reduced fish and invertebrate numbers. Subsequently with the drought breaking, with the return of flow, fish and invertebrates are back, although some species (e.g. River Blackfish have been slow to return). As well as forming scour pools, the structures also help in generating habitat structure by trapping particulate organic matter, such as twigs and leaves. Monitoring of the fish continues.
Overall the study was a success in that we learnt a lot about the nature of structures to put in sand slugs to generate habitat, about the responses of fish and invertebrates to the structures and their scour pools, and about the need to provide refuges for freshwater fauna to survive droughts. In terms of newly recognized "standards for ecologically successful river restoration" developed by the National River Restoration Science Synthesis Project, this success would score highly.
This project was funded by the CRC for Freshwater Ecology, the CRC for Catchment Hydrology, the Goulburn -Broken Catchment Authority and Agriculture Fisheries Forestry Australia.