Trial restoration approach at Silver Plains, Tasmania’s central highlands

It’s been almost a year since we commenced our eco-hydrology assessment and restoration planning for the Tasmanian Land Conservancy’s (TLC) Silver Plains Reserve. Now, the trial restoration process has begun, following a draft restoration plan which was completed in June 2026. You can read some background on the topic in this previous article introducing Silver Plains here. For reference, Silver Plains is a 6,595 ha reserve in Tasmania’s central highlands, consisting of sub-alpine forest, marshes and grassland, and supporting a number of threatened species, including Latham’s snipe, Tasmanian devils and eastern quolls.

A staged implementation plan is proposed, beginning with trial works at Bucks Marsh in winter/spring 2026, major works at Bucks Marsh in summer/autumn 2027, and expansion to other areas from 2027/28 onwards (e.g. Robson’s Marsh and Plough Marsh complex, Regents Plain, Daffodil Marsh and Simons Park). Wedgetail and Snipe Marsh above Bucks Marsh will not be restored for up to five years to support University of Tasmania (UTAS) research (i.e. these areas provide a control for restoration work at Bucks Marsh and are hydrologically connected).

The overarching restoration goal is to reinstate natural hydrological regimes across the reserve. This will be achieved by slowing the movement of water through the marshlands, raising water tables, restoring landforms and flow pathways, reducing erosion, and promoting recovery of wetland vegetation. However, the site poses many challenges: it is remotely located in the central highlands of Tasmania, access to marshland areas is limited, spoil banks along drains are often absent, marsh soils are highly organic and prone to erosion, and the site experiences sub-alpine conditions which typically translates to slower vegetation growth and recovery.

Different methods and materials are likely to be applied to the different situations we encounter, determined by factors such as: site conditions, spoil presence and availability, drain impact classification, presence of vegetation, flow volumes/catchment areas, slope, and presence of bedrock. Works methods will focus on complete backfilling of drains where this is possible, followed by the placement regularly spaced weirs, to create overland sheet flows, by blocking or rendering ineffective any drains where continuous backfilling is unable to be achieved. Chosen materials will be site specific and are likely to include inert materials like plywood sheets and rock.

Bucks Marsh Trial

As part of finalising the restoration plan, a small-scale trial of restoration methods has begun in the south-west corner of Bucks Marsh – the priority site for restoration in summer/autumn 2027. The trial is being undertaken to test materials, methods and feasibility of up-scaling the proposed manual approaches to restoration works.

Within this area we installed a series of marine grade plywood weirs across minor to moderate drains in early winter 2026. Ply is light weight, predominately comprised of natural materials, cost-effective, able to be pre-cut and distributed around site (minimising traffic), fairly robust, long lived (20+ years for marine ply), and easy to install. Ply was selected after much deliberation based on research, discussions with peers in NSW and ACT who have experience in highland peat restoration and a workshop with the TLC). Other materials considered included coir logs, logs/planks, mulch/brush packs, clods/in-situ spoil, sandbags and straw-bales.

The trial included testing different ply thicknesses (mainly 6 mm, 9 mm and 12 mm for minor to moderate drains), different ply sizes (ranging from a height of 175-300 mm and width of 600-2400 mm) and weir spacing (5 – 10 m). Whilst potentially appropriate for small drains, the 6 mm ply was deemed too thin for broader application and will be omitted from future works, due to concerns about its rigidity and durability. It is also likely that thicker ply (15-18 mm) will need to be applied to major drains to boost integrity and cope with greater flow impacts and/or pressure.

Weir spacing is important! Ideally, the water backing up behind weirs will maintain near complete saturation of the surrounding soil profile, and the water level in front of each weir will be of sufficient depth to disperse any overtopping water (if/when that occurs) and prevent erosion. Regularly spaced dams in drains act to slow water, allowing the soil to fully saturate and causing water to spill laterally out of the drains to mimic pre-drainage conditions. The surrounding slope will determine whether this water disperses more broadly in another direction, or re-enters the drain (and then flows into the next weir pool) immediately downstream. This dam type is likely to be most effective on low gradients and small to moderate drains.

The trial also enabled us to determine the most efficient method for installing boards and the need for any specialist tools. Board installation consisted of the following steps:

• Pre-cut plywood board to size (allowing for keying in at the sides – approximately half the drain width on either side, and 5-20 cm at the base depending upon the depth of the drain).
• Specifically, site where the board will go across the drain – prioritise areas that will direct water away from the drain, rather than back into the drain immediately downstream.
• Pre-cut a slot through the topsoil, vegetation and associated root mats along the line of the intended weir board placement. A specialised tool was designed and developed by NGT (in conjunction with a local metal fabricator / engineer) to assist with this task which has a 25 cm long and wide straight cutting face, a foot-plate for standing on (to drive it into the ground) and a handle for support and pulling out.
• Install the board into pre-cut line and hammer into position with a rubber mallet, using a specially designed ‘c’ bar to fit snugly over various sized plyboards and protect the top edge from direct blows.
• Hammer the board in until it sits 2-3 cm proud of natural surface either side and is locked into the base and sides as planned. V-notches have not been added to trial boards (where dispersal of flows away from the drain is sought) but will be considered for larger weirs during up-scaling, where overtopping is probable.

Approximately 30 boards have been installed to date and will be observed throughout winter/spring 2026 to determine performance and any need for adjustment in our approach prior to up-scaling for summer/autumn 2026/27 restoration works.

Observations to date (July-August 2026)

Both UTAS and NGT staff have conducted visits to the Bucks Marsh trial area over the late July and early August 2026 period. The marsh was very wet during this time, however the majority of the installed boards were effectively contributing to the reduction of flows and redirection of flows out of the drain and across adjacent marsh areas. These observations alone provide proof of concept, albeit with some tweaking required. Insights thus far include paying particular attention to the following:

• keying in of weirs at the sides and base (at least half the drain width on each side)
• the height of weirs (ideally a few centimetres or more above natural surface)
• spacing of weirs (closer than further apart to build in redundancy and to allow for incomplete effectiveness of some weirs)
• placement of weirs (ideally between two high areas with natural low areas behind each weir so that gathered water can escape to lateral areas).

Next steps

Detailed plans and logistics for restoration of Buck’s Marsh will be firmed up in coming months, informed by the outcomes of the trial, and discussions with TLC and others (contractors, material providers) in preparation for the commencement of works in earnest in summer/autumn 2026/27.

Silver Plains presents a significant opportunity to deliver large-scale outcomes in a high priority landscape, while concurrently developing new wetland restoration approaches that could be applied in future to other properties with similar potential in Tasmania’s Central Highlands.

Through a carefully planned, science-based approach, the project aims to reverse historical hydrological impacts, enhance biodiversity, support carbon sequestration, and improve ecosystem resilience in the face of climate change.

We look forward to finalising plans to capitalise on hydrological restoration opportunities across the reserve over the coming two years.

This work is being undertaken within a broader project ‘Building Ecosystem Resilience: A Tasmanian Model for Renewal at Silver Plains’ funded by The Ian Potter Foundation and led by the Tasmanian Land Conservancy.