## 3 Result and Discussions
### Alternative Wave Models  
After obtaining the bathymetric change model over a 10-year period from the erosion model, wave modelling was conducted to assess the impact of the bathymetric changes on wave conditions. Monthly wave roses were generated to analyze the wave height and dominant wave directions for each month. Furthermore, wave recurrence periods were calculated for 2, 5, 10, 25, 50, and 100 years. In alternative-1, using shore protection as one of the mitigation alternatives, wave heights along the pipeline route remained consistently low, owing to the protection provided by the shore protection measures. In contrast, alternative-2 with jetty protection and alternatives-3 with no protection exhibited significant wave heights in the channel and pipeline areas due to their open nature, dominated by swell waves characterized by long periods. Consequently, significant wave breaking was observed predominantly in areas near the shore. Furthermore, in alternatives-2 and -3, the dominant wave direction in the channel and pipeline areas was from the northwest. Across all alternatives, wave heights at the jetty area remained relatively low, facilitating jetty operations for 100% of each month or approximately 94% annually in the case of  
Figure 16: Bathymetric conditions model over 5 year (**A**,**C**,**E**) and 10 year (**B**,**D**,**F**) in each alternative (Alternative-1 shown in (**A**,**B**); Alternative-2 is shown in (**C**,**D**); and Alternative-3 is shown in (**E**,**F**)).  
Meanwhile, for the wave heights in alternative-2, which employs a 650 m long jetty protection, as depicted in Figure 19, it is evident that the wave heights are also around 1.2 m-1.3 m. The distinguishing feature of this alternative from model-1 lies in the dispersion of wave heights reaching into the bay area. Nevertheless, due to the presence of jetty protection, as indicated by the vertical yellow line in the Port area and along the west coast, the installations of gas pipelines and ship berths remain unaffected by these waves. With the mitigation scheme of model-2, the wave heights in that area range only from 0.3 to 0.54 m. However, model-2 has its drawback, as it may lead to suspended sediment transport at the southern end of the jetty protection due to incoming waves. To address this issue, the initially planned length of the jetty protection, which was 650 m, is optimized to 420 m.  
Figure 19: Alternative wave propagation model-2.  
Figure 20: Alternative wave propagation model-3.  
On the other hand, alternative-3, which involves no protective alternatives (Figure 20), exhibits a uniform distribution of wave heights at 1.2 m-1.3 m, impacting the gas pipeline installations along the coastal edge of Pulau Baai Port. The absence of protective measures exacerbates erosion, as there is nothing to impede wave energy from eroding the coastal edge and exposing the buried pipelines.  
Based on the annual extreme wave model data, recurrence periods were calculated using statistical concepts, particularly focusing on the 100-year cycle [44; 45]. The primary objective was to estimate the most critical scenarios for the design, especially regarding the structural capacity to mitigate wave impacts. Recurrence period calculations were performed using the Weibull method [7; 46] with k values of 0.75, 1, 1.4, and 2, and the Gumbel method, with respective to RMSE values of 0.021 m, 0.042 m, 0.041 m, 0.051 m, and