Hanna Swamp, a remnant wetland of the upper Merri, is ripe for restoration. It is vital that imminent planning decisions don't preclude this option. Hanna Swamp lies about 50km north of Melbourne on the eastern side of Herne Swamp near Wallan. The future of Hanna Swamp is the subject of a recent blog and a hard-hitting discussion paper from the Nature Glenelg Trust.
Despite agricultural drainage, Hanna Swamp's morphology persists across the bulk of its original footprint and it still temporarily inundates on a semi-regular basis. Natural wetlands are very forgiving ecosystems, capable of supporting plants that are especially adept at bouncing back after decent rainfall. Sustained recovery of Hanna Swamp is potentially only a single season away, as long as water is retained instead of drained away.
Photo: Spectacular habitat recovery at Scale Swamp, near Dunkeld, SW Victoria in 2017, 3 years after restoration. Prior to restoration, this site was largely devoid of native vegetation and has a broadly similar agricultural drainage history to Hanna Swamp. © NGT
Restoration of a wetland like Hanna Swamp is more cost and time effective than the effort required to create something approaching equivalent value in an urban constructed wetland. Also, restoration causes a lot less disturbance, because you are literally working with a natural landscape feature that already exists.
Like nearby Herne Swamp, Hanna Swamp is currently earmarked for development within Melbourne’s northern growth corridor, and it faces an uncertain future. Currently, early pivotal layout decisions are being made for this area in the Precinct Structure Plans being developed by the Victorian Planning Authority. Yet there does not appear to have been any detailed comparative analysis made between the legitimate choices as to how these catchments are ultimately developed. For example, wouldn't it be preferable for the original waterways, including in-stream features like Hanna Swamp and Herne Swamp, to be integrated into development designs and turned into community assets with multiple benefits?
These questions are discussed in detail by Mark Bachmann in the Nature Glenelg Trust Discussion Paper: Achieving Integrated Water Management of the Wallan Wallan Wetlands – Recognising gaps, understanding systemic obstacles to adoption, and identifying solutions.