Mangrove Cove

Delta
Mangrove Cove Management Plan
The reclamation materials appear to come from a variety of sources. Digging on the site
reveals large amounts of ‘kunkar,’ the calcrete material that underlies the St Kilda formation
in the Port Adelaide area. Whenever portions of the Port needed deepening, this layer had to
be removed. It is possible that some of the ‘kunkar’ material on the site came from the
excavation of West Lakes that occurred in 1974. Other materials include bricks, concrete,
asbestos (Messenger, 25/3/86) and slags of unknown origin.
The boat ramp that slopes down from the filled area to the natural surface has slag of
unknown origin exposed along its eastern edge, and is topped by a thick layer of ‘limestone
grits’ that were probably sourced from the Soda Ash Plant at Osborne.
Coastal acid sulfate soils (ASS) are formed during and after periods of seawater inundation,
such as occurred in the Adelaide region during the Flandrian Transgression. These soils are
quite stable while they remain inundated, and are usually referred to as PASS (potential acid
sulfate soils). PASS soils convert to actual ASS after they are drained. The mudflats,
saltmarsh and mangroves all occur on intertidal soils likely to be classified as PASS. While
these areas remain undisturbed and subject to daily tidal inundation, these potential acid
sulfate soils are unlikely to become actual ASS.
The management objective is to minimise any further degradation of the site and attempt
remedial actions where possible.
Strategies:
• Disturbance to the soils of the intertidal areas shall be minimised.
• Should any actions that could disturb areas of coastal acid sulfate soils be
contemplated, an impact mitigation plan shall be developed in cooperation with the
Coastal Protection Branch of DEH.
• The preferred treatment for the boat ramp area is revegetation, maintaining
biodiversity and improving amenity. The details relating to the methods and practical
completion of the project will be negotiated between the PAE Council and Newport
Quays, outside this management plan.
5.2.2 Hydrology
Mangrove Cove historically contained a small creekline that reached the Port River in the
Cove. This creekline was part of the estuary, and early records relate that the land drained by
the creek was swampy and subject to the tides. The salinity of the creek would therefore have
been quite variable, as one would expect in an estuary. In summer, high evaporation
combined with the tidal inundation would have resulted in periods of hypersalinity. In winter,
the swamp discharge may have been brackish.
The creek has been redirected from the Cove, indeed its original course is buried under
Rennie Road and the reserve now receives only the freshwater that falls on it. The ‘creek’ that
has developed in the Cove appears to be a drainage line that has formed in the lowest
remaining area of the Cove and that allows the daily draining of tidal waters. This creek may
become more defined over time as mangroves become dense on either side of it.
Groundwater around the Barker Inlet and under Port Adelaide occurs as a series of shallow
quaternary aquifers, some of which are located just below the natural surface. Salinity in these
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