Impact of reclamation on monsoonal circulation changes in Jakarta Bay

Abstract

The Jakarta Bay plays an important role in supporting maritime activities such as marine transportation, tourism, industry, and coastal communities. To meet the needs of the people in the future, it is planned to build islands (giant sea wall) through huge coastal reclamation. In oceanography-point-of-view, new islands formation is believed to modify natural coastal circulation in the region. Here, we investigated the impact of new islands formation on Monsoonal circulation and passive tracer distribution by performing a validated numerical model experiment with ROMS-AGRIF. The results show that natural Monsoonal circulation is characterized by eastward (westward) flow during the Northwest (Southeast) monsoon period, but mean circulation flows eastward. Water mass in the inner bay is flushed partially by water from western/eastern peninsula. With the presence of reclaimed islands, the Monsoonal surface flows are partitioned into channels in-between the islands. An intensification of the flows is found around a narrow channel. Furthermore, passive tracer of water, released in Ciliwung River estuary, indicated Monsoonal reversal spreading along the channels closed to the coastal mainland. Further experiment by changing channels width to be much smaller, the flows revealed are much weaker, was resulting in an accumulation of passive tracer around the estuary.