The Eighteen Mile Swamp

Extending from about 3.5 km south of Point Lookout to Swan Bay this great area of dense vegetation looks inviting from afar. Closer contact, however, reveals an environment challenging for human contact. Since its formation about 6,000 years ago it remains relatively untouched by mining and disturbance to the peat forming process. This occurs below the surface mat of tea-tree, reeds, ghania (a tall razor-sharp grass) and ferns as the sea level in this locality was up to 7 metres below the present level approximately 8,000 years ago and up to 1 to 1.5 metres above 6,000-6,500 years ago.

It has been determined that this back barrier swamp formed during a less than 1 metre fall in the sea level since. This allowed a new beach to form eastwards and thus prevented the westward movement of sea water. The swamp, which receives its water from the island dunes, contains Freshwater Creek which is barely discernible in much of the Northern section. It is surprisingly deep where it enters the sea water conditions of the mangrove and palm swamp adjacent to the shallow sea of Swan Bay. 

Naree Budjong Djara National Park sign.

In the last sixty years there has been a noticeable increase in tea-tree and weeds (groundsel, etc) in lieu of reeds in the southern and mid sections of the swamp. This may be caused by an increase in salt-water ingress from Swan Bay with a slight increase in sea level or the extraction of fresh water for the mainland. The peat in the fresh water area is about 10 metres deep and consists of 4 metres of fibrous peat overlying 6 metres of an older gel-like material of embryonic coal. Hydrogen sulphide gas is evident in the anaerobic decomposition of the peat. This gas is also more noticeable where sea-water enters in the southern area.

Periodic fires have influenced the swamp environment but the indigenous people may have used this as a hunting device. The swamp wallaby, which may have been hunted, is a fine red-golden coloured animal unique to the island. In dry periods fire can reduce the swamp to ash in a matter of days. The recovery of the vegetation, however, indicates that fire adaptation is a characteristic of the present dense vegetation. Fire may also have been used by the original inhabitants to allow easier access to the beach from the inland. There are middens within the swamp on isolated and rare sand-rises which indicate old aboriginal pathways. Mosquitoes are abundant, especially at night in the southern section, in spite of the presence of fish in all areas which feed on their larvae. This, as well as the disease inherent in the anaerobic bacteria, is another deterrent to human ingress.

Sand dunes indicate past severe south–east wind gales. These dunes intrude into the swamp and are only stabilized by the growth of vegetation. The steep sand escarpment west of the swamp was thought by many to be signs of a relatively recent incursion when the sea beat upon the base of these hills. Research recently, however, has determined that this was at a time before the swamp was formed about 6,500 years ago. In fact, the swamp is the historically most recent formation on the island.

The swamp also contains a mystery ship-wreck described by Fred Campbell of Amity in a manuscript handed to Tom Welsby before he died in 1898. He thought that it was the wreck of Pamphlett and Finnegan’s ship, positioned he described as 4 miles north of Swan Bay and a mile in from the sea. This is, of course, well into the swamp. All fire-blackened remains above water- level have disappeared since 1954. Enough descriptions exist to describe this ship as heavily built, oak-framed, sheathed in Muntz metal and containing copper and iron bolts and rivets. It has been described as 30 yards long, aligned as a bee- line north south with the bow facing north. The use of Muntz metal and copper defines a possible time of its construction. Another time bracket is that it was an apparently unknown wreck after Moreton Bay was settled. Fred Campbell gained knowledge of it from the tribal elders of Moongalba and Amity and wrote that the first white men the aborigines had ever seen were Pamphlett and Finnegan, the discoverers of the Brisbane River. Later, it was Welsby himself who researched this and wrote that they, with Parsons, had been wrecked on Moreton Island.

This suggests that the mystery ship was abandoned further south by its crew at sea and may have been a drifting wreck washed ashore onto the beach to await an intense cyclonic storm or a tsunami to carry it into the swamp. Of the over 6,000 known Australian ship-wrecks only one appears to satisfy these conditions.

Enterprise mine encroaching on swamp.