8120; 8220. Barrier Islands, South Gipppsland

Introduction:

East of Corner Inlet between Barry Beach and McLoughlans Beach is a group of low, predominantly sandy islands that are an extension of the Ninety Mile Beach and Gippsland Lakes region. There are five major named islands - Snake, Little Snake, Sunday, St. Margaret, and Clonmel and over 20 smaller islands that consist entirely of late Pleistocene and Holocene marine sediments, (sand, mud and organic material) and constitute one of the major sets of barrier islands of the Australian coast. The islands are complex form and origin. They represent a phase of extensive and continuing marine and aeolian sedimentation that has produced several large islands surmounted by well defined sand ridges with dune grass, scrub and woodland vegetation. Shorelines and tidal flats that border the islands are typically sandy - the ocean beaches consist of medium to coarse sand and shells, while finer sands and occasionally mud are the dominant materials of the intertidal areas. On the sheltered shorelines of the tidal flats, embayments and creeks, is and extensive Avicennia marina mangrove) community and a Salicornia or Arthrocnemum saltmarsh. The smaller, low inlets may consist only of mangroves and salt marsh growing on a sandflat or mudflat.

Basically there are five semi-enclosed embayments or tidal inlets between McLoughlans Beach and Wilsons Promontory, the largest of these being Corner Inlet, although most of this is outside the present study area. Although some exchange of water takes place between these tidal basins, each receives and discharges tidal water through a well defined inlet that opens into Bass Strait. A branching network of channels distributes the flood tide into the tidal basin but because of the sandy nature of the substrate, this network is not clearly defined or deeply incised as the tidal channel system of Westernport Bay.

Powerful tidal currents are generated through the entrances and these have produced conspicuous ebb and flood tidal deltas at the Port Albert Entrance, Kate Kearney Entrance, and Shallow Inlet and to a lesser extent at the New Entrance. The configuration of these deltas and of the spits and barrier beaches that flank them is subject to rapid change due to the movement of large sand bodies by waves and tidal currents.

The islands, tidal entrances, tidal channels and flats are geomorphological feature of National significance. They are a unique segment of the barrier system of the Ninety Mile Beach - Gippsland Lakes region, and provide an outstanding example of the processes of barrier island formation including the development of multiple beach ridges, lagoons and swamps, tidal creeks, tidal deltas, and tidal washovers. As well as providing localities for the monitoring of sediment dynamics associated with marine and aeolian processes, they are of critical importance in the analysis of the evolution of the entire coastal barrier system between Wilsons Promontory and Lakes Entrance.

The tidal and wave generated currents in these inlets give rise to a complex sediment movement pattern and the morphology of shoals and channel can change rapidly. Coastal engineering works in the intertidal and tidal channel areas may cause considerable change in the existing processes of sediment distribution.

It is recommended that disturbance to the island and channel systems east of and including Snake Island, be kept to a minimum. Dredging, widening and straightening of the entrances and channels would significantly degrade the value of these features as also would tidal flats. The sites described in the following [ages are regarded as those being most critical in defining the character and dynamics of this island and tidal system but it is stressed that the integrity of these could be adversely influenced by engineering works in adjacent areas, particularly those which are part of the same tidal flooding and drainage network.