Eco-hydrology as a driver for tidal restoration: Observations from a Ramsar wetland in eastern Australia

Abstract

Land reclamation projects and the installation of drainage infrastructure has impacted coastal wetlands worldwide. By altering water levels and inundation extent, these activities have changed the viable ecosystems onsite and resulted in the proliferation of freshwater species. As more than 50% of tidal wetlands have been degraded globally over the last 100 years, the importance of this issue is increasingly being recognised and tidal wetland restoration projects are underway worldwide. However, there are currently limited sites where large-scale reintroduction of tidal flushing has been implemented with the explicit aim to foster the growth of a threatened ecosystem. In this study, the tidal restoration of an internationally recognised Ramsar listed wetland in eastern Australia is described to highlight how coastal saltmarsh can be targeted by mimicking inundation depths and hydroperiod across the 410-ha site. Coastal saltmarsh is particularly important to this site as it is part of the east Australasian flyway for migratory birds and the minimum saltmarsh extent, as listed within the Ramsar’s limits of acceptable change, have been breached. To recreate coastal saltmarsh habitat onsite, water level and hydroperiod criteria were established based on similar vegetation patterns within the adjacent estuary. A calibrated 2D hydrodynamic model of the site was then used to test how the preferred inundation criteria could be applied to the largest possible restored wetland area. Once optimised, a synthetic tidal signal was implemented onsite via automated hydraulic controls. The onsite vegetation response over an 8-year period was assessed to highlight the ecosystem response to controlled tidal inundation and denoted substantial saltmarsh expansion during the period. The techniques applied onsite have successfully met the restoration targets and can be applied at similar sites worldwide, offsetting sea level rise impacts to natural inundation hydroperiod.

Blue carbon ecosystem monitoring using remote sensing reveals wetland restoration pathways

“…Saltmarsh growth would be expected to plateau once all suitable bare areas have been colonised, with an upper growth limit controlled by elevation/inundation and pasture grass competition (Streever and Genders, 1997). In our study, most bare areas were colonised by saltmarsh after 4 years, with landscape diversity also increasing during this time (Supplementary Figure S6), aligning with timeframes of other nearby rehabilitation sites (e.g., ~5 years; Glamore et al, 2021;Laegdsgaard, 2006). This indicates that saltmarsh rehabilitation via natural regeneration can occur relatively quickly, providing insight into trajectories of blue carbon restoration at saltmarsh rehabilitation sites in south-east Australia.…”

Land Tenure, Ownership and Use as Barriers to Coastal Wetland Restoration Projects in Australia: Recommendations and Solutions

“…Despite this global momentum and increasing recognition of the importance of restoration as a crucial management tool for marine ecosystems (Saunders et al 2020), marine restoration projects are yet to be undertaken at a large scale in Australia (Gillies et al 2015;Saunders et al 2022;Waltham et al 2020), although there are some promising examples of major restoration projects that have been implemented (see e.g. Glamore et al 2021). The reasons for this are multifactorial, including the cost of implementing projects (Bayraktarov et al 2016), and the lack of dedicated and fit-for-purpose restoration policy, requiring proponents to engage with time-consuming and expensive processes designed for permitting development and other harmful activities (Shumway et al 2021).…”

Modelling the response of mangroves and saltmarshes to sea-level rise: model development and validation

“…Assessment of differences between observations and simulations in the context of the error in SET measurements indicates that it is only in the saltmarsh at French Island and Kooweerup where differences exceed the error. Modifying tidal behaviour is reported to influence restoration success (Glamore et al, 2021), and on-going monitoring of the influence of tidal modification of surface elevation trajectories is recommended.…”