Coastal conditions and long-term topographic changes of Tanjung Benoa Beach on Bali Island, Indonesia

Abstract

Tanjung Benoa Beach on Bali Island, a globally recognized coastal resort with well-developed coral reefs, is experiencing beach erosion. This study aimed to formulate measures against the beach erosion, with a quantitative analysis of the coastal mechanisms through field observations, aerial photographs, satellite images and bathymetric data. The results indicate that the beach erosion on Tanjung Benoa Beach has occurred over time due to the longshore sediment transport, although the rate reduced by a construction of a groin. Additionally, the eroded area can be considered as a closure system of sediment transport between two groins at both ends, where accumulation and erosion of sand occur simultaneously. Based on these results, sand back pass was proposed, and its implementation plan was examined through numerical calculations for three-dimensional beach topographic changes. The numerical calculation compared a case of beach nourishment alone to adding four groins, suggesting that beach nourishment without groins is more effective for achieving the target beach width, maintenance plan efficiency and the high demand for beach uses on Tanjung Benoa Beach. This plan represents one of the few instances of sand back pass in Indonesia and promotes sustainable solutions to beach erosion, balancing beach utilization and conservation.