## 4 Conclusions  
In summary, Pulau Baai's sediment is predominantly sandy, with sedimentation and erosion primarily influenced by longshore currents induced by wave direction. Substantial abrasion and significant coastline changes occur, particularly in alternatives-2 and -3, driven by longshore currents leading to transport. Simulation for alternative-3 in the jetty area experiences erosion, transforming the region into open water over approximately two years of model simulation. Depth alteration or erosion in the channel and pipeline route within alternatives 2 and 3 ranges from 1 to 3.2 m. Unlike alternative-1, which closes all wave access and has shore protection in the middle of the coastline area, the erosion depth value in alternatives-2 and -3 is influenced by the wave height that spreads evenly at the jetty point and pipe installation because the beach in the central area is not blocked by any building protection. The most suitable mitigation alternative for issues in Baai Island Port is to use alternative model-2 with jetty protection. This alternative, initially planned at 650 m and optimized to 420 m, is suggested to prevent erosion in the jetty area where the ship rests. Potential sedimentation is anticipated in certain sections of the existing subsea pipeline route. After ten years of erosion, a significant increase in wave height (Hs) within Pulau Baai's waters is observed: 0.22 m for alternative-1 and 1.32 m for alternatives-2 and -3, representing an elevation of approximately 1.1 m from existing conditions. Given substantial waves in the Pulau Baai area, there is a considerable risk of vessels colliding with exposed pipelines in the absence of shore protection. This is due to the lack of obstacles diverting the incoming wave direction, pushing vessels into the area impacted by abrasion. Wave heights for alternatives-1, -2, and -3 at the jetty are relatively low, allowing year-round operational capabilities for alternatives-1 and -2 due to dominant wave heights remaining below 0.5 m. In alternative-1, wave heights along the pipeline route are kept low due to the presence of shore protection. Conversely, alternatives-2 and -3 exhibit higher wave heights, allowing for the consideration of a 100-year wave height with a magnitude of 2.2 m from the northwest direction. Reviewing cost effectiveness and mitigation effectiveness for abrasion issues, alternative-2 is a suitable protection to be applied in the coastal area of Baai Island Port. The results of this research on mitigation alternatives for abrasion are expected to be applicable to locations with similar morphological conditions and issues along the Baai Island Port coastline. Conceptualization, resources, and validation, M.I. ; methodology and formal analysis, M.H.I. ; investigation and project administration, A.N.R. ; data curation and software, R.R.R.A. ; writing--original draft preparation and writing--review and editing, A.N.A. All authors have read and agreed to the published version of the manuscript. This research was funded by PT. Inti Teknik Solusi Cemerlang (ITSC) and the APC was funded by PT. ITSC. Not applicable in the study. The datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request. The authors declare no conflicts of interest.