THE IMPACT OF WIND SURGE ON SEA LEVEL HEIGHT IN THE COASTAL AREAS OF PEMANGKAT (CASE STUDY: 27TH, 29TH, AND 31ST DECEMBER 2018)

• Main Author: Isnandiahening, Arrumi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86575
• Institution: Institut Teknologi Bandung

This study aims to analyze the influence of wind (wind surge) on sea level changes in the coastal area of Pemangkat during December 2018, focusing on December 27, 29, and 31, 2018. Wind surge is a phenomenon where sea level changes are caused by strong, sustained winds blowing in a single direction, especially during extreme weather periods such as the active Asian Monsoon in DJF (December, January, February). These strong winds can affect sea water movement, resulting in significant sea level rises or falls. This study employs a two-dimensional (2D) hydrodynamic modeling approach using the Delft3D software. The model integrates tidal and wind data from ERA-5 as the primary inputs for simulation. ERA-5 wind data was selected due to its high resolution and ability to accurately represent global wind conditions. The study uses two main scenarios: a no-wind scenario (pure tide) and a wind-inclusive scenario (a combination of tide and wind). In the first scenario, the simulation was conducted to observe tidal dynamics without wind influence. The second scenario involved a combination of tide and wind to analyze the direct impact of wind on sea level changes. The simulation results indicate that wind affects sea level changes along the Pemangkat coast. Generally, the wind causes a sea level increase of 0.06 m. In the case studies of December 27, 29, and 31, 2018, when wind speeds reached their highest points, the wind contributed to an increase in sea level during low tide, recorded at 0.05 m, 0.02 m, and 0.11 m, respectively. From the analysis, it was found that wind surge contributed approximately 9.23% to the sea level rise. During the highest wind speed period on December 27, 29, and 31, the wind surge contributed more to the sea level increase during low tide, with contributions of 4.95%, 2.78%, and 16.67%, respectively. This indicates that wind surge has a greater impact on sea level rise during low tide when the wind is at its maximum strength. Model verification was conducted by comparing simulation results with predictions from the Tidal Model Driver (TMD) and the Geospatial Information Agency (BIG). The verification results show that the hydrodynamic model used has very high accuracy, with an average correlation coefficient (R) of 0.989, a Root Mean Square Error (RMSE) of 0.079 m, and a Mean Absolute Error (MAE) of 0.069 m. This high accuracy demonstrates that the model is reliable in predicting sea level conditions in the Pemangkat coastal area. Furthermore, an analysis of regional and local current patterns in the study area shows that the strong westerly winds not only cause sea level changes but also significantly affect current patterns. Strong winds result in more intense current movements in the coastal area. This study emphasizes the importance of considering wind factors in sea level change studies in coastal areas, particularly in the West Kalimantan coast. The results of this study are expected to contribute significantly to the scientific literature on hydrodynamic dynamics in coastal areas. Additionally, this research highlights the importance of accurate wind data in hydrodynamic model simulations, such as global wind data from ERA-5, to produce more accurate predictions. This study is expected to serve as a reference in developing better sea level simulation models for coastal areas in the future.