The effect of reclamation on the significant wave height changes in Jakarta Bay during Hagibis and Mitag typhoons

The intensity and frequency of extreme events due to climate change in the future will most likely increase, as suggested in the sixth IPCC assessment report. Climate change has been propounded as one of the prominent causes of the ocean’s extreme events, particularly those associated with atmosphere–sea interaction occurring in the tropical region of Indonesia. A typhoon is an extreme event that forms in the Western North Pacific Ocean and causes changes in oceanographic parameters in a region far from its origin point. Thus, the goal of this study is to investigate how extreme events like Hagibis and Mitag typhoons affect the Significant Wave Height (SWH) in Jakarta Bay, particularly in the reclamation areas. SWH changes in Jakarta Bay due to the reclamation of Kita, Maju, and Bersama coastal areas have been simulated during both typhoons from 19th to 27th November 2007. The simulation was run from 1st October to 31st December 2007 using the Simulating WAve Nearshore (SWAN) model, and it was performed for two scenarios of pre-reclamation and post-reclamation. The analysis used a lagged correlation between wind speed magnitude in the study area within the South China Sea (SCS) and Indonesian Archipelago and SWH in Jakarta Bay from 19th November to 13th December 2007. It was found that the amplification of SWH changes in Jakarta Bay was associated with swell propagation from the SCS and Philippines, where Hagibis and Mitag typhoons were formed. The result exhibited that the most affected SWH due to the peak phase of Hagibis and Mitag typhoons (23rd November 2007) in Jakarta Bay was after an 11-day travel time, which was on 4th December 2007 compared to other dates. Hence, SWH during post-reclamation with regard to the three established reclamation areas (Kita, Maju, and Bersama coastal areas) responded to changes in SWH in Jakata Bay by up to 38.82% and down to 1.75% in Maju and Kita coastal areas, respectively.