Shoreline Erosion on a Low Coral Island in Fiji : Causes and Consequences

Yanuca Island is a 50 Ha low emerged coral limestone island, located near the south west coast of mainland Fiji in the South Pacific. Developed on the island is an international resort complex. Local Fijian land owners and resort staff provide accounts of shoreline erosion on the island over recent years. An investigation into the processes responsible for this erosion found several influences were important. A comparison of air photos over the last 50 years indicates there has been significant evolution of the coastal geomorphology of Yanuca Island. In the 1980s, sand mining and vegetation clearance led to instability and narrowing of a coastal sand bar at the north end of the island. Along the south coast, current measurements show that there is a strong longshore drift, driven by the persistent southeast trade winds. This is responsible for the removal of beach deposits and the resulting exposure of underlying beachrock. The erosion problem is probably compounded by a reduction in the supply of biogenic sand from adjacent fringing reefs, due to overfishing and degradation of the reef ecosystems. Tropical cyclones have also caused much coastal erosion in recent years. Finally, a causeway connecting to the eastern side of the island has a dam effect and influences the flow of currents around the island. Consequences of beach loss and sand mobility include sediment infilling and deterioration of adjacent lagoon conditions. Several management actions to alleviate coastal erosion problems on Yanuca Island are suggested