Flood., 1986:

"The variable shape of the cays reflects changes in the wind-induced wave patterns.  Erosion or accretion may occur depending on the balance of sediment movement onto or away from the cay and/or along a particular section of the beach in response to long shore drift.

Variation in wind conditions

Variations in the wind direction will influence the position of the nodal point of the wave refraction and diffraction pattern.  Consequently the alignment of the cay will alter accordingly.  Cays are subjected to wind fluctuations on three time scales.  The first is the annual cycle of seasonal fluctuations.   This is clearly evident in the records from the weather station on Heron Island (Fig.4).  Between February and August the east-south-easterly to south-easterly winds dominate, whereas between September and January variable northerly to north-westerly winds also occur.  On some occasions where strong north-westerly winds prevail for a short time the nodal point may move to the south-west or even to the south-east as has been documented on Heron Island (Flood 1974, 1979b). The overall seasonal wind pattern will produce a net migration of the cay towards the leeward, north-west part of the reef." 

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Citation and/or URL

Flood, P.G. 1986, Sensitivity of coral cays to climatic variations, southern Great Barrier Reef, Australia, Coral Reefs, 5: 13-18.

Spatial Coverage

Heron Island, Southern Great Barrier Reef

Temporal Coverage

1962 to 1980

Update Frequency

Not applicable

Other Information

Flood, P.G. (1974) Sand movements on Heron Island, a vegetated sand cay, Great Barrier Reef Province, Australia.  Proc 2nd Int Coral Reef Symp 2:387-394.

Flood, P.G. (1979b) Geomorphology of Tyron Island and Reef.  Queensland Naturalist 22:113-126.