New Town Rivulet outlet renewal – sea club sedge translocation

Our team recently completed a key phase of the New Town Rivulet outlet renewal project for the City of Hobart. The project aims to replace ageing concrete embankments with a more natural estuarine environment, improving bank stability, estuarine health, biodiversity, and public amenity.

During the planning and approvals phase, our team undertook a natural values assessment and identified a population of Bolboschoenus caldwellii (sea club sedge) within the development footprint. Listed as rare under the Tasmanian Threatened Species Protection Act 1995, this species is limited in both distribution and population size in Tasmania. Approximately 52.5 linear metres, about 43% of the local population was likely to be affected by works.

In response, we developed a comprehensive Translocation Plan on behalf of the City of Hobart. With a permit approved by the Department of Natural Resources and Environment Tasmania (NRE), we carried out the on-ground translocation. Mature B. caldwellii plants, including their rhizomes and surrounding soil, were carefully excavated and relocated to nearby semi-submerged marsh habitat that closely replicates their original conditions. We prioritised mature plants to maximise survival, drawing on insights from earlier wetland planting projects.

To provide further protection, we also established an ex-situ insurance population. Seed and vegetative material were collected and propagated off site, where they will be maintained for five years. This will safeguard against loss and provide a source for reinforcement planting if needed.

To support long-term outcomes, our team developed a five-year monitoring and maintenance program, aiming for at least 75% survival. This work strengthens an existing population of B. caldwellii outside the impact area, and with improved natural habitat conditions we anticipate a net benefit to the species, with potential for the local population to expand beyond its original size.