The Role of Hurricanes in the Development of Reef Islands, Ontong Java Atoll, Solomon Islands

Abstract

This paper describes recent geomorphic change on reef islands of Ontong Java atoll, Solomon Islands and discusses the nature of the 'steady state' equilibrium that has been proposed for cays and motus. The effects of a hurricane in 1967 are analysed through detailed field mapping in 1971, 1972 and 1986, and with reference to evidence from earlier charts and air photographs. It is concluded that the hurricane represents a high-magnitude low-frequency event necessary for the long-term replenishment of sediment on shorelines, but that in the short term such storms will seem to have mainly destructive effects. Since 1967 rubble ramparts thrown up by the hurricane have been largely reworked into stable landforms, mainly through the agency of more frequent, lower-magnitude storms. In parts of the atoll where coarse sediment was not deposited in 1967 there is a widespread retreat of seaward beaches. Such coastal erosion does not necessarily imply that islands have been destabilized by vegetation removal, climatic change or a rising sea level. It is only by considering the long-term sediment budget and the relaxation time of landforms in relation to major hurricanes that decisions can be reached about whether particular reef islands are in equilibrium with process.