Other impacts on coral reefs - The Great Barrier Reef: An Environmental History - page 185

strip in the Heron Island lagoon. The creation of the landing strip required the
removal of around thirty-five coral 'bommies' (micro-atolls) from the proposed
landing are a. 2 T he Director of the QDHM, A. J. Peel, wrote to the Queensland
Treasury stating that there would be no objection to the removal of the bommies
in the lagoon 'provided that any necessary blasting is kept to a minimum and small
charges are used '. 3
Subsequently, between October 1966 and October 1967, the channel and harbour
at Heron Island were dredged to allow easier access for boats across the reef to the cay.
The dredge spoil was used to create a bank around the boat channel in an attempt
to prevent sediments washing into the depression; spoil was also deposited as a spit
on the south-western side of the islan d. 4 T he channel altered the appearance of the
Heron Island reef, which was photographed by the marine scientist, Isobel Bennett,
before and after the creation of the channel; two of her photographs are reproduced
in Figure 12.1. Following the creation of the channel, concern was expressed about
rapid erosion as a result of changing sediment flows over the Heron Island reef.
Erosion was reported at the western end of the island from 1960 to 1966: the period
since the initial breach in the outer rim of the reef was made.
However, the full impacts of the channel were not immediately discernible, as
a report about the impacts of the creation of the boat channel, written by Patricia
Mather, Honorary Secretary of the GBRC, in 1971, stated:
The effects of the most recent activity - the cutting of a channel through the
reef crest at the south-west end of the cay and the excavation of a harbour
with half-tide walls cannot yet be evaluated. But build-up of sand along the
southern side of the cay - where it was previously being lost - and loss of sand
around the north-west and western parts appears to be taking place rapidly as
a result of the change in flow characteristics past the island and over the reef,
caused by the presence of this deep channel through the reef . 5
Inevitably, however, a significant area of the coral reef was affected by the
construction of the channel. Another report, in 1970, claimed that 'virtually no
recolonisation' of corals had occurred since the creation of the channel (Royal
Commission into Exploratory and Production Drilling for Petroleum in the Area of
the Great Barrier Reef, 1974, p724). In addition to those reports, many oral history
informants observed changes at Heron Island reef associated with the dredging of
the boat channel, especially changes in sedimentation in the channel and in the
surrounding portions of the reef fla t. 6 One stated that near the channel, adjacent
to the island, 'the entire top of that reef dropped probably in the order of four
centimetres […] because of the speed of draining of the lagoon that used to occur
at that end '. 7
Other channels and tracks were created in reefs besides the channel at Heron
Island. Another boat channel was cut through the reef at Lady Musgrave Island;
at that reef, a report by Steers (1938, p56) during a geographical expedition to
the Great Barrier Reef stated: