Monday, 27 April 2009

Arcuate ridges and other landforms

If you have ever travelled along Ballarto Road then you may have noticed the sand ridge which follows Hobson’s Road at Rythdale. This is an Arcuate ridge, or a curved ridge or one shaped like a bow. The Rythdale ridge is three kilometres long and up to 100metres in length.


The Rythdale Arcuate ridge can clearly be seen in this 1980 aerial. Ballarto Road cuts across the centre of the photograph, above the oval trotting track. Hobsons Road runs towards the top of the photograph and the curved object is the arcuate sand ridge. On the left of the photograph are man made drains to carry the water from the Deep Creek and Toomuc Creek to the Bay, part of the Koo-Wee-Rup Swamp drainage works.

There is also an acruate ridge on which the township of Cardinia is built on. This ridge rises five to eight meters above the surrounding countryside and is partly due to the depression of the adjacent area caused by the compaction of the peat soils after the Koo-Wee-Rup Swamp was drained. The Rythdale and the Cardinia Ridges are the remains of the walls of ancient lake beds.


This aerial photograph was also taken in 1980 and shows the town of Cardinia, built on the arcuate ridge. Starting at the bottom of the photograph, is the Cardinia Recreation Reserve. Ballarto Road runs along the right of the Reserve to the top of the picture. The town is bi-sected by Dalmore Road to the left of the picture, and Cardinia Road to the right. The curve of the sand ridge can be clearly seen.

These ridges are considered to be sites of Geographical and Geomorphical statewide significance. You can access a  list of Victorian sites of Geological and Geomorphical significance, here.  These landforms are part of our early history, plus they also give me another opportunity to show you some of our extensive collection of aerial photographs which are kept in our Archive.

The Casey Cardinia region has a landform of International significance, the Western Port Bay Tidal Watershed. This is the area north east of French Island , between the Lang Lang River and Palmer Point. This area is a tidal divide and the dynamics of the tides here effect the tidal flow in the rest of the Bay. The sea floor sediments of the watershed 'are of considerable interest for the data they hold concerning the development of the on-shore Swamplands' due to the fact that they record historic changes in the sea level.


The inter-tidal flats between Lyall Inlet and the Bunyip River are of National significance and are shown here in this 1968 aerial. The South Gippsland Highway bi-sects the photograph from left to right. The first inlet from the left is Lyall Inlet. The farm complex is Harewood house, built for William and Annabella Lyall in the 1860s. The straight channel on the other side of Harewood is Cardinia Creek and the channel on the right is Moody Inlet. If you click on the photograph to enlarge it you will see the Cardinia Creek Boat Club marinas where Moody Inlet crosses the South Gippsland Highway.

On a National level, the inter-tidal flats between Lyall Inlet and the Bunyip River outlet (between Tooradin and Koo-Wee-Rup) are significant as the area shows the impact of the drainage of the Koo-Wee-Rup Swamp on the adjacent coast land and is a reference point for measuring the rates of coastal change. They are shown in the photograph above.


Of regional significance, is the tidal meanders of Sawtell Inlet at Tooradin as the area is a ‘clear display of of the development of flood tide meanders' and is thus a site to study tidal flow in a narrow inlet.


This 1986 aerial shows the town of Tooradin and the meandering Sawtell Inlet. The other inlet on the right is Evans Inlet. Tooradin's mud flats are also apparent.