Brisbane River - Environmental Concerns

Environmental Concerns

During the 19th century and early 20th century, the river's surface was periodically choked by large swathes of the noxious weed known as water hyacinth. The plant was originally imported from South America.

Environmentally, the river is in a poor condition and has been so for many years. In 2000, the Brisbane River estuary did not meet the national guidelines for environmental standards. The lower reaches received a very poor rating in the 2008 Healthy Waterways report, an annual assessment of river water quality. The major causes of pollution are excess nutrients, hydrocarbons, pesticides and bacteria which become concentrated in the river and its sediment after flowing off surrounding lands. The river is also considered too murky and it is not recommended to swim in its waters.

Historically, the river was actively dredged by Boral Sands Inc, ostensibly to make the river navigable. The constant extraction of river bed material by dredges has had considerable effect on the river. These impacts include increased turbidity, bed and bank erosion and changes in tidal hydraulics. The tidal nature of the river and the generally muddy nature of the sands removed by dredging created a woefully sludgy clayey sediment load in the river which did not clear.

The efficacy of dredging the river upstream of the city reach to make it "navigable" was always in doubt, and the effect of the artificial sediment load in Moreton Bay grew to concern environmentalists worried that sediment was choking sea grass paddocks which were grazing territory for dugong. In a meeting concerning the matter in October 1996, including two State Government Ministers and three Mayors, an agreement to cease the dredging of sand and gravel from the river by September 30, 1997 was formed. Boral Resources Pty. Ltd. resisted the agreement, but ultimately all dredging was stopped by the agreed date.