Snag placement and fish habitat hold under record floods, addressing key operational risks and barriers to stakeholder participation in re-snagging projects (#113)
Ecosystem responses to re-snagging were the most frequently evaluated applied intervention in large-scale river restoration demonstration reaches, such as Native Fish Strategy (2003–2008). Whereas, there has been limited opportunity to test key operational hazards and associated community concerns. This Central Tablelands LLS and DPI Fisheries partnership addresses one such hazard of reinstated snags moving during high-velocity events (flooding), and damaging infrastructure, moving onto adjacent floodplains or realigning to cause bank erosion. In 2008, 12 ‘snags’ and rock complexes comprising 83-snags were placed within a 2-km reach of the Lachlan River at identified high priority sites adjacent to populations of the endangered Macquarie Perch (Macquaria australasica). Electronic pit tags were inserted into snags to monitor movement during periods of high flow. Additionally, standardised fish assemblage sampling was undertaken within the survey reach and adjacent reaches to assess differences in fish diversity, biomass and spatial distribution associated with the reintroduced habitat. Snag sites were 12-km upstream of Lachlan River at Reid’s Flat gauging station (412027), where the Lachlan River peaked at 7.48 metres with a mean daily discharge of 58,825.60 megalitres per day (ML/day) during the March 2012 record flood. Post-flood monitoring confirmed all snag placements held under 2010 and 2012 flood velocities. This result demonstrates that locally appropriate re-snagging techniques and materials can mitigate perceived flood risk associated with snag movement and infrastructure damage, and alleviate a public concern which may be a barrier to securing the critical involvement of landholders and community in such projects.