Floods that lingered for weeks along the northern coast of Central Java have become a stark reminder of how fragile the region has become. Experts warn that the area is entering a critical phase, with some districts facing the risk of sinking if no serious mitigation steps are taken. The Kota Lama, or Old Town, area of Semarang is even predicted to turn into the sea by 2045.
One of the strongest warnings comes from the Director of Walhi Central Java, Fahmi Bastian. He says the northern coastline, or Pantura, has reached a point where land subsidence and rising sea levels are creating conditions that could reshape the region within the next two decades. According to him, the Old Town area of Semarang could sink and turn into the sea by 2045.
This prediction aligns with the increasing signs of stress across several cities. Semarang, Pekalongan, and Demak have all experienced severe impacts. Flooding on Jalan Pantura Kaligawe, for instance, lasted more than a week. Land subsidence has also continued at concerning rates.
“Land subsidence in Semarang is around 8–12 cm. But it isn’t the same every year, sometimes 5 cm. So by 2045, areas like Kota Lama could already become part of the sea,” Fahmi said.
In Pekalongan, the situation is even more severe. “In Pekalongan, land subsidence is actually higher than in Semarang, at 12–15 cm but averaging around 8 cm,” he added. Meanwhile, in Sayung, Demak, sinking land is linked to coastal erosion as waves continue to sweep away soil while mangroves vanish, leaving the shoreline unprotected.
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Fahmi views the large-scale flooding that hit Pantura two weeks ago as a strong signal of the region’s deteriorating condition. He explains that the threat of submergence is not driven solely by tidal floods or extreme weather, but by accumulated ecological damage from upstream to downstream.
Rivers flowing into Semarang and Demak can no longer accommodate incoming water because they have not been properly normalized. “When we talk about floods, the rivers that flow into Semarang and Demak actually need to be normalized again because they can no longer hold the volume of water coming in,” he said. The unfinished Semarang–Demak sea wall project has added to the challenge, especially with its retention pond still incomplete.
Upstream areas such as Mijen and Ngaliyan have also contributed to the problem. Once functioning as water catchment zones, these areas have been weakened by housing developments built without regard for environmental carrying capacity. As these zones shrink, more water flows downstream, overwhelming rivers that are already struggling.
According to Fahmi, the damaged mangrove ecosystem is another major factor. Mangrove forests, which play a crucial role in reducing the impacts of the climate crisis, have been neglected in many coastal development plans across Central Java.
He urges the government to act immediately, stressing that Pantura has entered a critical stage and requires serious intervention to prevent further decline.
