Rapid formation of a barrier island and beach erosion caused by large-scale excavation of reef flat on carbonate beach

A large-scale land reclamation plan was adopted in the 1990s for Sanur beach on Bali Island in Indonesia, in which the reef flat was excavated in order to create a navigation channel and an island was newly built using the excavated sand. This plan was put into effect in 1997. However, the wave height and wave direction have greatly changed in the calm zone of the reef coast extending thanks to the existence of a very shallow reef, because of the extreme increase of the reef flat depth due to the excavation, resulting in severe beach erosion as well as the formation of a new barrier island landward of the excavated offshore hole. This study is aimed at the investigation of this phenomenon through field studies and numerical simulation of waves and wave-induced currents on the reef, taking Sanur beach as an example. It is concluded that the formation of the barrier island and beach erosion was a result of this large-scale excavation of the reef flat.