MURRAY RIVER: Matthew Flinders & the Coastal Landforms of SE Australia

On Flinders' chart the following description appears, along what is now called the Coorong; 'low, sandy shore'. This coastline offered no direct clues to the existence of the Murray River. There is a blank on his chart at the position of the mouth - he missed viewing and charting that area. Even if he had seen that portion of coast it is not certain what could have been determined of the Murray Mouth from sailing by at the 'standard' distance from the coast. Ironically, Flinders had hoped to find on this expedition (ie. the Investigator's traverse of southern Australia) an access to an 'Inland Sea'. The lower Murray River and its mouth were discovered later by an overland and river expedition led by Charles Sturt; many rivers of Australia are not particularly prominent from the sea (with their relatively low water flows, especially in low season, and shallow entrances). 'Low land ... Low sandy shore, topped with hummocks of almost bare sand ... Discovered by Capt Baudin 1802' - Extract from Flinders' chart (Encounter Bay)
The Murray River is the largest river of Australia in terms of catchment area and average annual flow. It flows to the sea near the historic port of Goolwa after splitting into channels that pass through a maze of islands. These islands are composed of soft sediment. A series of barrages controls the flow, preventing salt water from moving upstream in years of low river flow. The barrages also raise the river level in its lower reaches. While the river is significant to much of southeastern Australia, its flow at the mouth is lower than its flow further upstream. The demands of domestic and agricultural water use and high rates of evaporation cause the river flow to decline over its lower course.
The Murray Mouth, where the river finally reaches the sea, is far from spectacular. Sand banks, bars and shallows spread out over a wide area between low islands and coastal dunes. The river's course is not clearly visible, and little water volume appears to flow into the sea. From the Hindmarsh Island observation point, the ocean breakers of Encounter Bay can just be seen in the distance, beyond the Mouth. Adjacent to the Mouth, long, narrow sand spits (shaped by waves and currents) extend to the north-west and the south-east, forming part of the land's 'border' with Encounter Bay.	Photo 1: Mouth of Murray River, from Hindmarsh Island
Shells are numerous on the sands of the Murray Mouth. They are tossed onto beaches by waves during storms. Eventually shells are ground into small fragments which become part of the sand mass. Shellfish live in shallow waters where habitat is suitable and food supply available. Shellfish would have made up part of the food supply of the indigenous people of this region.	Photo 2: Beach surface, near mouth of Murray River, Hindmarsh Is
With time the Murray Mouth has largely choked up with sand deposited by the river and coastal currents. This has reduced tidal flow, made navigation more difficult, and at times closed the river mouth. A project to improve the Murray Mouth through dredging was planned to take place over late 2002 - early 2003. It is estimated that about 2 million tonnes of sand is located around the river mouth; the project aims to remove 400,000 tonnes (about one fifth) of this through dredging and pumping over a time period of seven months. The equipment should operate non-stop for 200 days, pumping away the equivalent of a beach a half kilometre long, 10 metres wide and one metre deep, every 2.5 days!	Photo 3: Part of signboard, showing mouth of Murray River, complex of channels, sand and silt islands and barrage locations
Importantly, this project is expected to improve the flow of tidal waters to (and hence the 'ecological health' of) the Coorong National Park. The Coorong is a dune and lagoon complex and vital waterbird wetland habitat that forms the eastern bank of the Murray Mouth, stretching along the southeastern shore of Encounter Bay.
Hindmarsh Island is a relatively large island within the complex of channels at the Murray Mouth. Prior to the Hindmarsh Island bridge's construction access to the island was more difficult. The bridge was built in the 1990s after some considerable delay; it had been held up through a dispute involving the developer and members of the Ngarrindjeri community. The Ngarrindjeri are the traditional dwellers of the Murray Mouth and surrounds.	Photo 4: Hindmarsh Island Bridge, Goolwa
Goolwa is the port at the mouth of the Murray River. It is possible to take a paddle steamer ride through this interesting area. In earlier days paddle steamers, with their ability to travel in shallow waters, were particularly suited to the waterways of the Murray River and its tributaries.
Salt buildup on the surface is a situation that occurs over much of Australia. It generally happens in low-lying areas of poor drainage, low rainfall and little topographic relief. It may be 'natural' (e.g. the salt lakes of northern SA and elsewhere), but human action through agricultural practices can promote the problem. Tree clearing in irrigated and dryland farming areas has received much of the blame for increasing salt incidence.	Photo 5: Small salt lake, Hindmarsh Island
Some people believe that widespread salt buildup (and related issues) could be the nation's major environmental problem. The situation is sufficiently widespread and serious to suggest a national environmental action strategy in response. Of interest is the concept of 'inland salt' - whereby sodium chloride salt is evaporated and harvested on a commercial scale from underground water in the Murray Basin. This removes only a small proportion of the catchment's total annual salt buildup, but it is a potentially useful start. Further research is proceding with the assistance of the CSIRO, and as there is a possibility that the removal of other valuable mineral salts from the ground water may take place, an economic impetus could eventually make a positive difference to this environmental problem.
Murray River - upstream Well upstream, near the NSW-Victorian border, the Murray River (shown right, along with overflow channels), is a significant stream. To much of inland southeastern Australia it offers holiday, recreational and transportation uses, attractive scenery, domestic and agricultural water supply, fishing, habitat and environmental water flow, and importantly, serves to drain considerable areas of the three states and the one territory of the south-east.	Photo 6: Murray River meanders and floodplain, near Berri, SA
Near Berri much of the land on the river floodplain is allocated for environmental reserves and forestry, and used for boat launching, picnics and camping. Some has suffered salt invasion, and is presently subject to restoration efforts. Nearby, at somewhat higher elevations, are large irrigated orchards and vineyards. Along the river numerous national and conservation parks, forest lands, leases and private property have been combined into the Bookmark Biosphere Reserve. The Reserve offers habitat protection for numerous plant and animal species.
Lake Mungo / Willandra Lakes - a region of geomorphic significance The Murray Basin is a large region with many surprising and interesting features. Well inland, between the catchments of the Darling and Lachlan Rivers, along the course of the Willandra Creek, is an area that is presently dry, but which used to hold large freshwater lakes. Significant populations of animals (including the famous mega-fauna such as the Diprotodon - a giant wombat-like creature) and people lived here. The Lake Mungo area (photos, right) is World Heritage listed due to the amazing geomorphic features, the climatic and geomagnetic records associated with its landforms, and its ecology and archaeology. As recent erosion rates have increased dramatically following European settlement, the dunes to the east of Lake Mungo have been rapidly denuded, exposing layers that reveal times (thousands of years ago) when the area was well settled by the ancestors of today's aboriginal people. Evidence for the most ancient human rituals so far discovered on earth have been found here. The longest dune forms a cresent-shaped feature on the entire eastern side of the lake called a lunette. The dunes of Mungo were built by prevailing winds under conditions quite different to those of today; hence they represent a valuable record of past environmental conditions. The dune-building environment prevailed during the Pleistocene (the 'Ice Ages' of the past 2 million years). Note that human settlement is much more recent than this.	Photos 7: Mungo National Park A: Kangaroo on Lake Mungo bed; Mungo Lunette (Walls of China) in background B: Actively eroding dune of the lunette C: Lake Mungo bed from lunette (at sunset); the lake shoreline used to be near here Lake Mungo MAP
The materials removed from this region are carried by wind or water in various directions. Wind moves particles in the prevailing direction; thus the active dunes are migrating eastwards, away from the lake bed. Water travels downhill under the influence of gravity; thus particles moved by water eventually work their way westward into the Murray-Darling system, forming (a small) portion of the mass of fine materials carried in suspension and ultimately deposited lower down the catchment along the river banks (or out to sea).
Interestingly, Lake Mungo and a vast area between eastern and western Australia, was a sea some millions of years ago. However, Captains Flinders and Baudin were much too late to discover that channel!