6. Noosa River DMP Ver0 (Combined)

        “Two Avicennia marina (Grey Mangrove) were recorded in the intertidal zone of the replenishment area
        along Gympie Terrace. Seedling mangroves and one established A. marina were recorded at the
        interface of the existing and proposed new extraction areas at Hilton Esplanade.”
        “It is important to limit the placement of any sediment that may adversely affect soil permeability,
        especially around mature trees, which are more prone to suffer than young trees. Ideally, all areas close
        to the tree trunk should be kept at original ground level.”
        “While most of the marine plants along the foreshore could be avoided, one mangrove [tree number 3 on
        the tree survey plan in Appendix D] [Figure 8] requires management of replenishment spoil to minimise
        impacts. Two options have been suggested:
                 1. Replenishment material be place at a depth so that the pneumatophores are not completely
                 covered (i.e. leave at least 2 cm of the pneumatophores exposed); or
                 2. Place replenishment material on either side of the tree protection zone of this specimen and
                 allow natural processes to move the sediment.”
        The other mangrove within the impact area [tree number 26 on the tree survey plan in Appendix D] had
        no visible pneumatophores at the time of the site inspection and was located within an area subject to
        current erosion control measures (i.e. coir logs [Figure 9]”
        “The tree protection zones of all other marine plants within the replenishment area along Gympie Terrace
        can either be avoided or will benefit from sand replenishment around the root zone.
        Many of the Casuarina glauca along Gympie Terrace have had the roots undermined by erosion. Without
        replenishment of the sand along this reach of the river, there is a risk these trees will fall [Figure 10]”
While management of only one marine plant (out of 43 marine plants identified), was specified in the Marine
Plants Survey, in order to implement the controls, the limit of works (tree protection zone) needed to be identified
and pegged out prior to works. Given that this DMP is to support an ongoing annual dredging campaign, and
pneumatophore exposure will change over time, it is proposed that prior to dredging a survey of marine plants is
undertaken and any tree protection zones (that require management due to pneumatophore exposure) are to be
pegged out prior to commencement of sand replenishment.
The tree protection zones for T3 (the mangrove currently at risk of impact) is 2.64m (Figure 8). Out of the six
mangroves identified in the marine plants survey, the tree protection zones varied from 0.12m (mangrove
seedlings) to 6.0m (mature plant) (Table 3).




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