Restoration works commence at Devil’s Corner (Moulting Lagoon), east coast Tasmania
Nature Glenelg Trust (NGT), in partnership with NRM South, have been undertaking independent eco-hydrological assessments and developing hydrological restoration plans for priority properties within or adjacent to the Moulting Lagoon and Apsley Marshes Ramsar sites since 2020. Investigations at Devil’s Corner commenced in 2025 and previous blogs can be found here: Introducing Devil’s Corner and Monitoring begins at Devil’s Corner.
Devil’s Corner is located on the periphery of Moulting Lagoon between Swansea and Bicheno and comprises a commercial vineyard and surrounding areas of pasture, woodland, wetland and saltmarsh. Legacy artificial drains have impacted the natural hydrology of areas of saltmarsh and wetland, resulting in decreased extent, condition and altered water regimes. The site is unique in that areas adjacent to Moulting Lagoon are now largely managed for conservation, and they typically have a native vegetation buffer with gently sloped surrounds. This provides the opportunity for future, seamless coastline and habitat migration in response to predicted sea level rise.
A restoration plan was developed for Devil’s Corner in March 2026 and implementation of that plan commenced in August 2026. The overall aim of restoration works was to reinstate a more natural hydrological regime and salinity gradient across the system, seeking to allow for more natural, low intensity tidal connections between Top Hole and the lagoon, and improved retention of freshwater in areas north of Top Hole and at Middle Hole.
Middle Hole
Middle Hole has no direct tidal connection. It appears to be fed primarily from freshwater inflows from the surrounding catchment in winter/spring and dries down through warmer months of late summer/autumn. The base of Middle Hole is below sea level (-0.15 mAHD) and is likely connected to groundwater or subsurface tidal influences. Water quality is brackish, with salinity increasing as the wetland dries down, and increasing during periods of catchment inflows.
Restoration actions for Middle Hole focused on backfilling the drain which had been cut into the side of the wetland to lower the sill level and direct outflows to Moulting Lagoon. Works will aim to re-establish the natural sill height and increase wetland depth, inundation and extent.
The drain reduced the natural sill height of the wetland, meaning that it could only fill to 0.3 mAHD (0.45 m water depth). Backfilling the drain would result in a restored sill level of 0.5- 0.6 mAHD (0.65-0.75 m water depth), with low points in the adjacent track becoming the overflow points.
Restoration works at Middle Hole were undertaken on the 17th -18th August 2026. The spoil bank was completely intact along the eastern side of the drain and was used to backfill the drain and knit together natural land surfaces on either side of the drain. The drain was backfilled from the wetland to the track, effectively blocking the main culvert.
Top Hole
Top Hole is highly connected to daily tidal exchanges in Moulting Lagoon, with daily sea water inflows keeping water levels in Top Hole permanent and salinity levels similar to that of Moulting Lagoon. Tidal exchange is currently restricted via an undersized culvert beneath the track. This restriction results in tidal ingress and egress not equalising in Top Hole and surrounds.
Restoration works at Top Hole focused on the replacement of the culvert with two similar sized culverts to increase flow capacity and facilitate more natural inflows and outflows. Restoration of the area northwest of Top Hole are on hold due to site conditions (see Next Steps below), but will be implemented by the end of 2026.
Culverts were replaced on the 18th of August 2026 with works taking place from the track, minimising impact to saltmarsh in adjacent fenced areas. The existing culvert was replaced by two round concrete culverts, effectively doubling the potential volume of flows. The track surface was reinstated to the existing condition post culvert replacement.
The water flowing out of Top Hole and upstream areas significantly increased upon culvert replacement, and continued to do so for some time post works, immediately validating this restoration action.
Next steps
The smaller drain remaining in an area northwest of Top Hole was too wet to complete works during August 2026. We will revisit this area in drier times with a smaller machine to backfill the drain and redirect natural freshwater inflows from the catchment along their original flow path, to re-establish natural hydrology and connection between freshwater catchment inflows and tidal flows.
Our in-situ water level data loggers and baseline vegetation information will help us to monitor change at works areas and ultimately the achievement of restoration goals over the long term. We will continue to keep you informed on site recovery in the months and years to come.
This project is funded by the Australian Government’s Natural Heritage Trust and delivered by NRM South, a member of the Commonwealth Regional Delivery Partners panel.
