Effects of coastal structures on the shoreline change in Phan Thiet bay, Vietnam

Abstract

This thesis examined the effects of coastal structures on shoreline change in Phan Thiet Bay, Vietnam from 1988 to 2021. This thesis explored two key objectives; that were the investigation of historical shoreline changes and the effects of structures on shoreline based on the comparison of simulated shorelines with and without structures by using GENESIS model. Moreover, the SWAN model was used for simulating wave data which is an important input for the GENESIS model.

From the shoreline evolution results, it was found that the land loss rate ranged from 0.9 to 8.7 ha/year in 1988 to 2016, while this loss rate increased up to 11.2 ha/year or 83% of the eroded coastline in 2016 to 2021. Moreover, the results found that the shoreline change rate was strongly correlated with the presence of structures and the frequency of typhoons.

The GENESIS model effectively simulated the shoreline in the Western area and the Eastern area in Phan Thiet Bay, with an average Mean Absolute Error (MAE) of shoreline change rate as 2.34 m/year and 5.32 m/year, respectively. The results from GENESIS model reaffirmed the predominant longshore sediment transport direction in this study area was East to West. For the effects of structures to the shoreline change, it found that the beach reclamation project affected the erosion areas up to 1600 m away from its location, while groins and seawalls influenced adjacent shorelines up to 2500 m and 1700 m, respectively. In conclusion, this study contributed results on the historical shoreline change and effects of some specific structures on shoreline change in Phan Thiet Bay, providing fundamental data for applying the coastal structures in future coastal erosion resilience project in this area.