Breathing new life into Sloping Main

On a spring day, with snow-capped Kunanyi in the distance and not a breath of wind, TLC ecologist Matilda Terry arrived at Sloping Main Reserve to find shallow pools of water spread across the saltmarsh.

Australian shelducks gathered at the water’s edge, while white-faced herons foraged among the beaded glasswort (Sarcocornia quinqueflora), the dominant plant across the marsh. From the surrounding forests and woodlands came the calls of striated pardalotes, fan-tailed cuckoos and black-faced cuckoo-shrikes.

‘For the first time on my visits, the saltmarsh was holding pools of water – and it brought the landscape to life in a completely different way,’ Tilly said.

The grasslands between the saltmarsh and the forest edge were alive with flame robins, Australian pipits and white-fronted chats feeding on insects. Wombats grazed nearby, native grasses responded to recent rain, and wedge-tailed eagles circled overhead. Along the beach, the sand was scattered with the moulting shells of spider crabs, while resident hooded plovers fed along the shoreline.

What Tilly was seeing followed an ocean-driven storm surge, which pushed seawater back into the wetland for the first time in more than three decades. The surge moved into a system where tidal connections had only recently been restored, allowing water to spread across the marsh.

The marshland has always filled with freshwater after rain to support abundant life. What was missing was slow, distributed movement of water across the landscape, along with regular tidal exchange with the ocean.

Sloping Main’s saltmarsh is not a permanent lake. It is a naturally wetting-and-drying system, shaped by slow freshwater flows from the land and periodic tidal exchange with the sea. Over time, drainage and levee construction had altered this balance – water rushed through the marsh instead of spreading and lingering, and tidal flows were largely cut off.

Repairing the flow of water

This flush of life followed major restoration works completed several months earlier, in autumn 2025, across two key wetland systems at Sloping Main – Burdens Marsh (Prices Flats) and Mungaratya/Turners Lagoon. These works were led by Nature Glenelg Trust (NGT) in partnership with TLC.

The work was guided by a simple aim: to restore natural hydrology so the wetland could function as a healthy, diverse saltmarsh again – without the need for ongoing intervention.

In practice, this meant slowing the movement of freshwater across the landscape, reconnecting tidal flows from the sea, and restoring natural landforms so water could spread, pool and drain in response to changing conditions.

Burdens Marsh sits at the heart of this story. Decades of agricultural modification had left it crisscrossed with drains, levees and embankments designed to dry the marsh for grazing. These works crossed the marsh’s subtle contours and disrupted the interaction between saltwater and freshwater systems that underpin healthy saltmarsh.

Those structures have now been removed. Drains were backfilled, and the ground reshaped to restore the marsh’s natural micro-topography. Even small differences in elevation matter here, shaping where water spreads, how long it sits, and which plants are able to grow.

Just to the east, restoration at the freshwater Mungaratya/Turners Lagoon required a different approach. Drainage works from the 1960s had been built over the lagoon’s natural outlet, making it impossible to know exactly where the original overflow point once sat. To manage this uncertainty, the team installed a temporary geofabric spillway with adjustable sandbags. This allows water levels to be monitored and fine-tuned as the lagoon refills, before the outlet is permanently stabilised.

Together, these works have achieved the project’s initial objectives. Freshwater now moves more slowly across the marsh instead of being channelled rapidly to the sea, tidal exchange has been restored, and natural landforms are once again guiding how water spreads and recedes. Importantly, the system is now functioning largely on its own, with minimal need for ongoing operation or maintenance.

A wetland shaped by history

To understand why this work matters, we need to look back at how the landscape has been altered over time.

Sloping Main Reserve protects a remarkably diverse landscape overlooking Frederick Henry Bay. Across its 670 hectares are ten threatened vegetation communities – more than any other TLC reserve. These include the nationally vulnerable Burdens Marsh, a freshwater lagoon, extensive dune systems and healthy coastal white gum forest.

Like much of Tasmania’s low-lying country, parts of this landscape have been heavily modified. Drains were first dug by convicts in the 1820s and later expanded by settlers to make seasonally inundated land suitable for farming.

At Burdens Marsh, an old timber weir and levee built in the early 1990s further altered water movement. Intended to control tidal exchange, the structure prevented saltwater incursions and changed how water moved through the wetland. After rain, water built up behind the levee and was released through the sluice gates in short, high-volume flows to the sea.

Its removal has allowed the creek line to once again breach, open and close in response to changing conditions – restoring a dynamic process that had been interrupted for many years.

Precision work, early signs of recovery

Before any machinery arrived on site, TLC and NGT spent more than a year studying the site’s eco-hydrology. This planning was strengthened by the knowledge of former landowner John Price, whose family has been connected to the area for more than a century.

Restoration works began in March, following months of preparation. Staff and volunteers removed almost four kilometres of fencing so workers could access the marsh. Excavator contractors then carried out precision earthworks over six weeks to backfill drains and re-establish natural landforms.

The changes Tilly saw on the ground during her spring visit are also visible from above. Even without major rainfall, aerial imagery shows water spreading and pooling across Burdens Marsh from the marine storm surges, guided by the restored contours of the land. These shifts are being tracked through repeat drone imagery as part of the University of Tasmania’s NatureScan project.

With the levee system removed, tidal flows can once again move between the marsh and the ocean. And with the drains now filled, freshwater spreads more gradually across the landscape, guided by restored landforms.

Taken together, these observations suggest the system is beginning to function more naturally. This is a naturally episodic wetting–drying saltmarsh, which seasonally holds water for several years before transitioning into a drying phase associated with more El Niño–dominated weather patterns – so the most predictable thing about this marsh is that its water regime is highly variable.

With natural water flows restored, Burdens Marsh, Mungaratya/Turners Lagoon and the surrounding wetlands are better placed to support native vegetation and wildlife, and to respond to increasingly variable conditions over time.

This project was made possible through strong partnerships, careful planning, and support from the Tasmanian Government NRE Tas Threatened Species Partnership Grant Program, the Purryburry Trust and individual supporters.

You can read NGT’s ecohydrological report here and find out more about the background to this work on the NGT website.

Banner photo by Dan Broun.