Rainbow Bay Beach Behaviour
Queensland's southernmost beach, Rainbow Bay, is known for its iconic beauty and world class surfing conditions. It is also one of the few beaches on the East Coast of Australia that faces north.The shoreline at Rainbow Bay is constantly moving but the overall beach width and shape generally fall into two distinct patterns.
In the first half of the year, the wave direction is more southerly. After being captured by the Jetty and discharged on the northern side of the River Entrance, or travelling offshore of Letitia in deeper water, large quantities of sand makes its way northward around the headland at Snapper Rocks.
Once sand has moved around Snapper, it slows down and temporarily builds up at Rainbow Bay. The beach continues to increase in width until sand at the northern end of Rainbow starts to flow around Greenmount headland.
In the second half of the year the average wave direction typically shifts more to the north, accompanied by strong northerly winds. This means that less sand moves around Snapper Rocks and into Rainbow Bay, and the beach begins to wash away. This creates a deeper Bay with a large separation between the swimming and surfing areas. As slugs of sand begin to move back around Snapper Rocks, a lagoon is sometimes seen as the sand migrates from the seabed to the beach.
Rainbow Bay, although always beautiful, naturally fluctuates with the changing seasons. Tweed Sand Bypassing has captured beach conditions on the southern Gold Coast beaches since the late 1990s. This information is used to track changes to the beaches caused by the impact of the seasons, storms, and sand delivery.
Rainbow Bay in January 2017
Image: Rainbow Bay’s seasonal pattern of retreat was clearly evident in January 2017. The almost constant stream of northerly winds and lack of swell throughout late 2016 and early 2017 reduced the natural northward flow of sand around Snapper Rocks. As a result, Rainbow Bay continued to change shape with the ocean moving closer to the dunes. Rainbow Bay should begin to increase in size once wave conditions become more south easterly, and sand is pushed along the coast and around Snapper Rocks.