A curious wombat takes a closer look at a newly installed leaky weir. Credit: The Quoin team.
This leaky weir has slowed the flow of water, letting much of it spread wide and seep into the soil. Credit: The Quoin team.
Our camera trap captures a Tassie devil passing through the area. Credit: The Quoin team.
The build-up of poo on each pole tells us birds love resting on our weirs as they pass through the area. Credit: The Quoin team.
By weaving fresh plant material into the structure, we hope to promote initial visitation by insects and birds. Credit: The Quoin team.
Location
Stocker’s Bottom
Ecosystem
Modified agricultural land
Benefits
Seed dispersal
Nutrient retention
Habitat creation
Species benefited
Flame robins and other passerine birds
Insects
Woodland fungi
In addition, there will be long-term benefits for bandicoots (linira) (Isoodon obesulus) and other small-to-medium marsupials
Aim
Disperse the surface water's energy, depositing organic matter and seeds along the bare channel to improve plant diversity and create animal habitat.
Background
When it was named early in colonial settlement, Stocker’s Bottom was an open woodland of native grasses and a seasonal wetland. Successive generations of owners did what they thought was best to improve grazing conditions for sheep, including eventually installing extensive drainage channels leading into the dam. These channels were an attempt to prevent an inundation of sandy soil in the wet season, but the trade-off was the exacerbation of dehydration in the dry times, and the channels backfilling the dam with sand, leaving it no deeper than 1.5m.
Our work to restore Stocker’s Bottom to an open woodland begins with these drainage channels, and more specifically, a solution called leaky weirs. In addition to slowing the flow of the water, allowing it to spread and rise, leaky weirs also stop nitrogen-rich animal droppings from entering the waterway. What’s more, these structures give the animals trafficking the area a place to rest and shelter from Wedge-tailed eagles (kurina) (Aquila audax) and other predators. We hope these weirs will also be used by birds, who will bring and disperse seeds, promoting revegetation. We've already witnessed extensive repeat use by small birds, noticeably male and female Flame robins (puwina) (Petroica phoenicea).
Approach
In June 2022, we conducted a first experiment, installing simple timber leaky weirs into a drainage channel in Stocker’s Bottom. The structures were made from material collected from a nearby overpopulated eucalyptus regrowth patch, woven tight and reinforced, and covered in calcined bone and at least 30 litres of biochar with open woodland leaf mould mixed through. The calcined bone will provide calcium and should extend the life of rotting organic matter exposed to moisture and oxygen. The results were encouraging, with all structures surviving and demonstrating their functional goals.
In October 2023, we installed three more structures, varying the shape of each to include a woven tree cage and branches of ripe seed pods. These new structures will be reviewed in Autumn 2024, and trees will be planted inside each, assuming no desirable flora recruitment occurs in the meantime.
Significance
This technique uses local, low-impact materials and simple hand-crafting techniques that have barely changed in tens of thousands of years. These structures bring no potential pollution into the ecosystem, and degrade into the environment in time, warranting no clean-up or disposal, unlike rusty fences.
We hope to include volunteers in future efforts, as every installation is its own creative experience.