The rise and fall (and rise) of Winston Island

Abstract

On 20th February 2016, the most energetic cyclone in recorded history, the category 5 Tropical Cyclone (TC) Winston, tracked through central Fiji causing widespread damage and loss of life. At its peak, ten-minute sustained wind speeds of 230 kph were recorded, with wind gusts of over 300 kph. The eye of the cyclone passed within 25 km of Qamea Island in northeastern Fiji, with the strongest winds occurring from the northwest.

After the cyclone had passed, a cay had formed on the southern fringing reef system ~1 km offshore of Qamea Island. The initial survey of the new cay (given the name Winston Island), found a mound of broken coral, sand and other debris some 1.8 m high by 105 m long and 15 m wide. Six weeks later the cay had reduced to only a fraction of the initial size (<30 m by 0.6 m high). It was expected that the cay was fated to disappear completely and the barrier reef flat to return to the pre-cyclone condition. However, 4 months later Winston Island had increased in size to be 126 m long and 2.0 m high, and has continued to slowly grow in size. While the formative mechanism was confidently determined (i.e. 2.5-3.0 m waves generated by TC Winston), and the initial chronic reduction in material was also intuitive, the mechanism which led to the subsequent rebuilding of Winston Island warranted investigation. This paper investigates the formative mechanisms that resulted in Winston Island and documents the subsequent changes to its morphology over the following year.