Tidal Flooding Continues to Threaten Java’s Northern Coast
A combination of meteorological and astronomical factors, as well as land subsidence, has triggered tidal flooding on the northern coast of Java.
SEMARANG, KOMPAS – To this day, tidal flooding still occurs along the northern coast of Java. Thousands of residents in several regions, including the cities of Semarang and Pekalongan in Central Java, were affected by the disaster yesterday.
According to the Meteorology, Climatology and Geophysics Agency (BMKG), extreme tidal flooding can occur at perigee, when the moon is closest to Earth, generating higher tides than usual in the Java Sea.
“From the astronomical perspective, the perigean effect has declined. It should have peaked around 14-20 May. So in this case, meteorological factors in the form of strong winds and large waves in the Java Sea are more dominant,” Eko Prasetyo, who heads the BMKG’s maritime meteorology center, said in Jakarta on Tuesday (24/5/2022).
Eko said the agency had issued an early warning on the possibility of perigean tidal flooding in the past week. Coastal areas that were alerted included Aceh, North Sumatra, the Riau Islands, Bangka Belitung, Lampung, Banten, Jakarta, West Java, Central Java, East Java, Bali, East Nusa Tenggara, West Kalimantan, South Kalimantan, East Kalimantan, northern West Papua and Merauke, Papua.
“However, tidal flooding is also influenced by local conditions, such as meteorological factors. The Java Sea is currently seeing strong winds and large waves,” he said.
According to the BMKG’s monitoring data, wind speeds in the Java Sea range from 20-25 knots and waves are reaching heights of 1.25-2.5 meters.
> Coastal Cities Facing Threat of Inundation
“This phenomenon could last until 25 May,” Eko added.
Continuing, Eko said that tidal flooding was now hitting the coast of Central Java from Pekalongan, Semarang, and Demak to Rembang. Additionally, tidal flooding had occurred along the northern coast of East Java, such as in Tuban and Lamongan.
“However, it’s not as bad as in Semarang, where an embankment was breached,” he said.
Land subsidence had also made Java’s northern coast vulnerable, Eko explained. Citing Rokhis Khomarudin, the leading expert in remote sensing technology at the National Research and Innovation Agency (BRIN), land subsidence was found to occur in coastal cities in northern Java.
According to satellite imaging, Jakarta is sinking between 0.1 and 8 centimeters per year, while Cirebon is sinking 0.3 to 4 cm per year, Pekalongan at 0.9 to 6 cm per year and Surabaya at 0.3 to 4.3 cm per year (Kompas, 17 Sept. 2021).
Embankment channels breached
Tidal flooding in Semarang was exacerbated by an embankment that collapsed on Monday afternoon. The breach of the 20 m-by-1.5 m embankment caused Tanjung Emas Port to be submerged in a flood measuring 1.5 meters high. Hundreds of workers had to evacuate the area on inflatable boats as the floodwaters continued to rise.
Flooding at Tanjung Emas Port halted all loading and unloading at the Semarang Container Terminal. At least 500 containers were submerged in the flood. The loading and unloading schedules for hundreds of containers were disrupted on Monday.
Once the electrical equipment for unloading containers, including power outlets, was deemed safe, shipping activities resumed at 11 a.m. on Tuesday.
“Operations at the Semarang Container Terminal have resumed. The pier and the container yard are relatively dry. Today, we are continuing with loading and unloading activities for three ships docked at the pier,” Semarang Container Terminal general manager I Nyoman Sudhiarta said on Tuesday.
According to Sudhiarta, the terminal remained focused on resuming loading and unloading activities. Losses due to the tidal flood would be calculated once shipping activities had resumed fully. The terminal management would also involve affected exporters and importers in calculating the losses.
State port operator PT Pelabuhan Indonesia (Pelindo) Tanjung Emas Region 3 in Semarang provided 3,600 sandbags for temporary repairs to prevent the floodwaters from spreading. PT Pelindo also distributed 32 water pumps with a capacity of 800 liters per second to reduce the water level.
Tanjung Emas Port general manager Hardianto said the port management had taken the necessary measures to elevate and reinforce the port, including elevate the container yard and adding water pumps. In the future, PT Pelindo would build new waterways and also elevate access roads.
Firsthand observations saw that tidal flooding continued to inundate the port on Tuesday evening. Outside the port, the floodwaters still reached half a meter high. In the port and adjacent industrial area, the floodwaters reached around 1 m.
Several factories had to send their employees home, although some were desperate to return to the factory to retrieve their motorcycles, which were lost on Monday saved.
As soon as news arrived that the embankment had been breached, “everyone fled immediately”, said Dewi Lestari, an employee at a garment factory in the Tanjung Emas Port industrial area.
“They were afraid of flash floods or tsunamis. It’s because we’re near the sea, so people had to evacuate without having the time to secure their motorcycles,” she added.
At around 2 p.m. an Tuesday, the embankment breach alarm went off. All employees at the port fled the area, racing against the seawater that quickly reached land.
My house immediately filled up with water until I couldn’t sleep.
The flooding also affected residential areas in Tanjung Mas subdistrict. “My house immediately filled up with water until I couldn’t sleep,” said Triana, a Tanjung Mas resident.
According to secretary Winarsono of the Semarang Regional Disaster Management Agency (BPBD), 1,255 families in Tanjung Mas and Kemijen subdistricts, or around 5,000 people, were affected by the tidal flooding.
Tidal flooding also hit Pekalongan and displaced 213 people. As of Tuesday, several areas, such as Degayu, Tirto, Panjang Wetan, Klego, Pasir Kratonkramat, Pangan Baru and Gamer subdistricts, were still inundated by 10 to 70 cm of water.
The flood was triggered by high tides that breached the 30-meter-long embankment along the Meduri River in Tirto village. According to Dimas Arga Yudha, head of prevention at the Pekalongan BPBD, sandbags were used to build a makeshift embankment to contain the floodwaters.
This article was translated by Kesya Adhalia.