3. Noosa Project Restoration Plan V12

SECTION 5 – RESTORATION SUBSTRATE
The restoration process involves the deployment of igneous rock, sourced from a local quarry, as the
primary restoration substrate. The rock will be augmented, at some sites, with a mix of oyster shell,
which forms a composite substrate. Upper surfaces of the rock substrate are augmented with oyster
shell, which may be seeded with live oysters and which locks into the rock substrate. Live oysters may
also be added to the substrate.

The design specifications and placement of restoration substrates, as described below and presented
in the attached specifications and drawings, have been certified by the project’s consulting coastal
engineers, International Coastal Management (ICM). The rock substrate is stable, and the shell stability
has been optimised by hand placement within the rocky matrix. The configuration has been optimised
to provide characteristics suitable for the desired habitat and minimises potential impacts on coastal
processes and the surrounding environment.

5.1 Rock substrate

The project will use a locally sourced igneous rock as the primary restoration substrate. The rock is in
the size range 150-500mm diameter and deployed in configurations, as oyster reef patches, that meet
engineering requirements related to movement, stability, erosion avoidance and minimisation of
sediment accretion as per the specifications for each restoration site.

Using rock (as opposed to oyster shell) as the primary restoration substrate has many advantages.
These include:

    •   Highly suitable as an oyster settlement substrate (rock oysters settle readily onto rock)
    •   Resembles natural oyster bed substrates
    •   Can be readily configured to meet engineering specifications for movement and stability under
        varying estuarine conditions
    •   Does not require complex engineering structures to support the shell to create vertical relief
    •   Can be deployed and configured using standard construction equipment and practices
    •   Readily meets ecological criteria for heterogeneity and rugosity and provision of habitats
        historically present in the estuary
    •   Raises the oysters above the benthic sediments of the river, helping ensure oysters attached
        to the rock are free from benthic sediments and have maximum exposure to water flow
    •   Offers multiple habitat opportunities across the intertidal and shallow subtidal ranges for
        multiple species
    •   Can be readily augmented with cured oyster shell to enhance rugosity, heterogeneity or
        chemical cues for oyster spat
    •   Is economically efficient to use, particularly if restoration is to occur at scale
    •   More ready passes the ‘naturalness’ test with stakeholders than shell in bags or cages (for
        example)

The use of local rock as a restoration substrate has been tried and tested by TNC and its state and local
government partners in sub-tidal oyster ecosystem restoration in Victoria, South Australia, Western
Australia and by the Department of Primary Industries (DPI) New South Wales in Port Stephens (Figures
5.1 and 5.2) for intertidal rock oyster ecosystem restoration.

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