## 3 Result and Discussions
### Coastal Abrasion
#### 3.3.1 Results of the Current Velocity Simulation with Alternative Model  
In alternatives-1, -2, and -3, the dominant current direction is toward the northeast. This is attributed to the dominant wave approach angle, forming an angle with the shore protection, resulting in the occurrence of longshore currents, as illustrated in Figure 14. However, in alternative-1, the area inside the shore protection exhibits predominantly calm current speeds, with a maximum speed along the pipeline route of 0.07 m/s, whereas in the jetty area, it reaches 0.12 m/s. Meanwhile, in alternative-2, which employs jetty protection, the maximum current speed is 0.71 m/s, and alternative-3 has a maximum current speed of 0.76 m/s. In the overall channel area of the alternatives, the dominant current direction is southeast, entering the bay. This is influenced by the dominant wave direction originating from the northwest, pushing water masses into the bay. A comprehensive overview of the statistical values for current speeds is provided in Table 3.  
Figure 14: Dominant flow patterns of alternative-1 (**left**), alternative-2 (**center**), and alternative-3 (**right**). Figure 13: Jetty protection as alternative-2 shown by a vertical line. 3.2 Results of Morphological Changes from the Results of Sedimentation Modelling for Each Alternative  
Figure 15 presents the morphological changes observed over 5 and 10 years in each alternative within the pipeline area. In the analysis of Figure 15A,B, it is clear that the implementation of alternative-1 effectively prevents erosion in the pipeline area, shielding provided by the shore protection. Contrarily, Figure 15C,D reveals that the use of jetty protection fails to halt erosion in the pipeline area, primarily due to the influence of dominant currents induced by waves. These currents transport sand or sediment toward the bay, resulting in sedimentation or siltation in the bay area. Notably, erosion levels in the channel and pipeline area range from 1 to 3.2 m. Similarly, the outcomes in alternative-3, as depicted in Figure 15E,F, indicate more severe erosion extending toward the jetty location, emphasizing the absence of any protective measures. The bathymetric and coastline conditions over 5 and 10 years in alternative-1 show no significant changes due to the protection provided by the shore protection, effectively mitigating coastal erosion, as depicted in Figure 16A,B. In alternative-2, as shown in  
Figure 15: Morphological change model over 5 year (**A**,**C**,**E**) and 10 year (**B**,**D**,**F**) within coastal area (**(**A**,**B**) represents alternative-1; (**C**,**D**) represents alternative-2; (**E**,**F**) represents alternative-3). \begin{table}
\begin{tabular}{c l c c c} \hline \hline \multirow{2}{*}{**Location**} & \multirow{2}{*}{**Statistics**} & \multicolumn{3}{c}{**Current Velocity (m/s)**} \\ \cline{3-5}  & & **Alt-1** & **Alt-2** & **Alt-3** \\ \hline \multirow{3}{*}{Pipeline} & Average & 0.01 & 0.18 & 0.20 \\  & Max & 0.07 & 0.71 & 0.76 \\  & min & 0.00 & 0.00 & 0.00 \\ \hline \multirow{3}{*}{Jetty} & Average & 0.01 & 0.01 & 0.02 \\  & Max & 0.12 & 0.06 & 0.14 \\  & min & 0.00 & 0.00 & 0.00 \\ \hline \multirow{3}{*}{Tide} & Average & 0.02 & 0.00 & 0.18 \\  & Max & 0.08 & 0.05 & 0.61 \\ \cline{1-1}  & min & 0.00 & 0.00 & 0.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Current velocity statistic values. Figure 16C,D, the bathymetric and coastline conditions in the channel area exhibit no significant changes, indicating a stable or equilibrium condition. However, outside the planned jetty protection area, erosion occurs, transforming the area into open water. In this alternative, the most substantial erosion occurs on the eastern coastline, resulting in a notable change in the coastline. The bathymetric simulation results for alternative-3 in Figure 16E,F reveal changes in bathymetry after 5 and 10 years in the jetty area, pipeline area, and channel area due to severe erosion in the absence of shore protection.