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Black Swan (dredge)
The ''Black Swan'' was the first bucket dredge used by the Swan River Colony (now Western Australia) to make its rivers more suitable for shipping. The dredge was operational from 1872 to 1911, when it was scuttled. Initially known as the Government Dredge,〔 it was renamed after being repaired and modified between 1887 and 1888. The dredging carried out by the ''Black Swan'' and other vessels had a significant impact on the river fauna and flora, including the black swans for which it was named.
==Design and construction==
The need for dredging the Canning and Swan Rivers, particularly around Perth Water, had been identified as early as 1865.〔 The shallow waters limited opportunities for trade, forcing cargo to be loaded and unloaded at the end of the Swan River, near Fremantle. In 1869 the government ordered a dredge from England, which arrived in segments at Fremantle in 1869 and was assembled in .〔 The dredge was long,〔〔 with a beam of ,〔 and a 12-horsepower steam engine, that could be operated at up to 32 horsepower when assisted by a flywheel.〔〔 There were 18 buckets attached to the bucket ladder, which was located in the centre of the vessel, and enabled dredging to a depth of approximately .〔〔
By 1887, having been left unused for several years, the steel bottom of the vessel had rusted through in various locations.〔〔 Repairs were made between 1887 and 1888. The bottom was replaced with Jarrah, and at the same time the bucket ladder was modified.〔 It was relocated to the bow, lengthened, and four extra buckets were added, which allowed the dredging depth to be increased to .〔〔
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