Cover Letter, DA Form 1, Plans, Owners Consent, Coastal Environment Assessment · OPW21/0049

Noosa Spit Coastal Protection Environmental Assessment                                                            16
Potential Impacts




5          Potential Impacts
5.1        Direct Modifications to Marine and Intertidal Habitat
           The beach nourishment zone occurs on land mapped below HAT and MHWS. There may be some
           removal of dune woodland vegetation associated with beach nourishment. Whilst this area supports
           sparse Cynodon dactylon, a marine plant listed under the policy, and sparse Melaleuca
           quinquenervia, this elevated dune scarp is not considered to support fisheries values.

           The western dispersive sand plug also occurs on land mapped below MHWS, which is unvegetated.

           Nourishment can be undertaken so that sand is placed around marine plants and should not impact
           on any living dunal vegetation. Around 46 fallen tree stumps (Melaleuca quinquenervia) that have
           remained on the beach following erosive events will be buried however. We understand these are
           considered fish habitat as they provide shelter for juvenile fish and are classified as marine plants.

           A survey of the subsurface to be disturbed during dredging has been undertaken; the disturbance
           footprint does not contain any marine plants (i.e. seagrass/macroalgae).

           The works will have the benefit of minimising further erosion and protecting marine plants associated
           with dunal vegetation being further eroded. Overall, the project is expected to have a positive
           outcome for marine plants over the longer term. Refer to Appendix C for further information.

           It has been identified that migratory wader birds may occasionally use intertidal flats to feed that
           would be disturbed during dredging. The migratory period for shorebirds peaks between October-
           November (arrivals) and March-April (departure); bird counts have significantly declined over the last
           five years or so, believed due mostly to disturbances to breeding areas internationally. During the
           survey period (2005-2019), breeding behaviour amongst shorebirds was limited to pairs of three
           resident species only; the Beach Stone Curlew, Australian Pied Oystercatcher and Red Capped
           Plover. Sand will be extracted from open channel areas, rather than stabilised sand banks where
           shorebirds are more likely to utilise, limiting disturbance to habitat or nests. Dredging will be confined
           to the winter months, when shorebirds numbers are lowest. Any areas to be dredged or nourished
           will be checked for nests prior to placement to further limit disturbances to shorebirds.

5.2        Water Quality
           This area predominantly consists of fine to medium grain quartz sand (Coffey 2011). Due to the
           sediment characteristics. it is expected that disturbed material will settle relatively quickly. The natural
           salinity levels will also likely result in the settlement of finer silts and clays.

           While the exact details of the dredging equipment will be determined by the appointed dredging
           contractor, a well-operated CSD will generate small turbidity plumes in comparison to other dredging
           methods. Most of the turbidity plume is caused by the rotating cutter head and is hydraulically
           removed from the receiving marine environment through the suction line and centrifugal pumps.
           Propeller-induced suspension of bed sediments during dredging or transiting in shallow water may
           also generate small and temporary turbidity plumes.




    G:\Admin\A10342.g.mpb.NoosaSpitSEMPdesign\03 approvals\R.A10342.002.00_Environmental
    Assessment.docx