Analysis of Longshore Drift Patterns on the Littoral System of Nusa Dua Beach in Bali, Indonesia

Abstract

Bali is one of the most popular tourist areas in Indonesia. With its coastline stretching 633 km, Bali has many beautiful beaches that have become world tourism attractions, thus making tourism the economic engine of Bali. The biggest priority of major tourism sites is maintaining sufficient beach width. However, based on a survey from Balai Wilayah Sungai (BWS) Bali Penida, Bali has suffered from a series of erosions along 215 km of its coastline, including Nusa Dua, in 2015. The location of the study area for this report is a 2.8 km stretch of coastline at Nusa Dua Beach. The erosion problem at Nusa Dua Beach was assessed by analyzing the longshore drift patterns. Simulations are required to assess this erosion problem, combined with the erosion rate and the simulated equilibrium shoreline for each sublittoral cell. To estimate the erosion rate, this study employed profile monitoring data of the beach obtained from 2003 to 2016. This advanced study was based on the mass conservation principle as a governing equation used to predict longshore drifts between sublittoral cells. The satellite image for every sublittoral cell was also used to check the equilibrium condition and estimate the predominant wave direction as the shoreline orientation. Nusa Dua Beach was found to suffer from the change of wave direction and the consequent generation of littoral drift after the reclamation project of Serangan Island located north of the Benoa strait. The correlation between the transportation of longshore sediments and the predominant wave direction indicates the effect of longshore drift in the system. The groin system also created a unique longshore transport pattern in the coastal area. The results obtained in this study can help manage the longshore drift system of Nusa Dua Beach and can be used to predict the beach area subject to erosion and deposition after every beach conservation project. Hence, a strategic plan for managing the shore target lines can be formulated.