The large number of victims and material losses in recent tsunami disasters in Indonesia’s Central Sulawesi and Sunda Strait areas have triggered criticism that the country doesn’t have an adequate, qualified disaster mitigation system.
On Sept. 28, a series of disasters struck Central Sulawesi, beginning with a 7.4 magnitude earthquake that generated tsunamis as high as 2 to 6 meters and swept the coastal cities of Palu and Donggala. The earthquake also triggered liquefaction of land in a housing complex in Petobo, Palu City, which sank hundreds of homes and public facilities and killed hundreds of people. At least 2,100 people died as a result of the multiple disasters and thousands more are estimated to still be buried amid financial losses of more than Rp18 trillion (US$1.26 billion).
The Sunda Strait tsunami struck on the evening of Dec. 22, sweeping the coast of Banten and Lampung provinces, leaving at least 430 people dead and more than 45,000 people displaced.
Rahmat Triyono, who heads the Earthquake and Tsunami Center of the Meteorology, Climatology and Geophysics Agency (BMKG), laid the cause of the Sulawesi tsunami to underwater landslides due to tectonic earthquakes, while the other was the eruption of Anak Krakatoa, a volcanic cone in the Sunda Strait that emerged in the 1920s in the crater left by Krakatoa, whose massive 1883 eruption was one of the most catastrophic in recorded history, killing at least 36,000 people.
As many as 90 percent of tsunamis are generated by earthquakes, with another 10 percent caused by underwater landslides and volcanic eruptions. "Tsunamis due to landslides are rare events but they occurred twice in Indonesia in a span of three months," Triyono said.
Poor Disaster Mitigation System
Sutopo Purwo Nugroho, a spokesperson for the National Disaster Management Agency (BNPB), said a combination of limited early warning systems, lack of knowledge and behavior of the community to anticipate tsunamis, inadequate shelters and poor planning were responsible.
"Therefore, disaster mitigation, including a warning system and community preparedness in facing disasters, is very important to save as many people as possible," said Sutopo.
Indonesia is especially vulnerable to volcanic eruptions, earthquakes and tsunamis because it sits astride the Ring of Fire, an active seismic area on the margins of the Pacific Ocean. At least 127 volcanoes –13 percent of the world's volcano population – are in Indonesia. Some are in the sea or on small islands which can cause tsunamis when erupting.
Despite the constant threat of such disasters, Sutopo said, Indonesia’s early warning system is clearly inadequate. For example, the country only has technology to detect tectonic earthquakes that trigger tsunamis, and not tsunamis triggered by volcanic eruptions. Thus there were early warnings for tsunamis in Sulawesi, but not in the Sunda Strait.
Sutopo said the absence of early warnings on the Sunda Strait tsunami resulted in people not having the opportunity to evacuate. "This has caused a lot of casualties," Sutopo said.
Moreover, tsunamis generated by landslides due to volcanic eruptions don’t show the same characteristics as those caused by tectonic quakes, such as receding sea water before high waves occur.
The weak early warning system was also considered as one of the causes of the many victims in Palu. The BMKG acknowledged the lack of tsunami detection equipment in the sea around the city, which meant – among other things – that there were no definite reports of tsunami height. The BMKG's initial statement immediately after the tsunami was wave height of 1.5 to 3 meters. In fact it reached 6 meters and even more in some areas.
Sutopo apologized for the non-functioning of 22 floating tsunami detection buoys to accurately record wave heights. They ceased to function seven years ago – in 2012 – because they were damaged or stolen. Indonesia now only uses seismographs, global positioning system equipment and tide gauges to detect tsunamis even though the equipment is less effective and less sophisticated.
Although many things need to be done to improve the disaster mitigation system, the government is considered reluctant to allocate more funds for disaster mitigation and handling.
"In practice, the budget (for BNPB) every year actually goes down," Sutopo said. "This has resulted in our inability to mitigate disasters, both for structural mitigation related to the provision of tools and preparing communities to be ready to face disasters."
In addition to the weak early warning system, the number of casualties and damage to buildings in the two tsunamis increased because of the location of the disaster sites. According to BNPB data, the area most affected in the earthquake in Sulawesi was Palu, with more than 1,700 people dead and thousands more estimated buried.
The city faces no volcanic threat, but the region sits on the Palu Koro fault, one of the most active in Indonesia. In addition, the most populated areas in Palu City are in the bay area, where they are prone to be hit by tsunamis – just what happened during the September shake.
Homes in more than 300 hectares of Palu City were also destroyed by liquefaction, including a densely populated area in Petobo and Balaroa, as the underlying earth turned to jelly. In the Sunda Strait tsunami, the number of permanent buildings on the seashore also resulted in many casualties and damage. Some 1,778 houses and 78 lodgings and shops were destroyed.
Minister of Public Works and Housing (PUPR) Basuki Hadimuljono said people had built in no-go areas on the Sunda Strait coast. Many destroyed houses, he said, were only about five meters from the beach even though legally the minimum distance to the shoreline is 100 meters.
"The buildings are really on the shoreline, so it is dangerous. Moreover, it is very close to Krakatoa," he said.
In general, data from the National Disaster Management Agency show that around 150 million people in Indonesia could be affected by earthquakes, and 3.8 million others could be potentially hit by tsunamis. Those in tsunami-prone areas have only 20 to 40 minutes typically to save their lives because tsunamis in Indonesia are local. They don’t roll in from thousands of miles away, as happened with the Boxing Day tsunami that devastated Phuket and Sri Lanka.
Lessons from Two Tsunamis
BNPB spokesman Sutopo said the 2018 disasters have provided valuable lessons about the importance of disaster mitigation. He reminded the government not only to provide tsunami detection sensors but also to build a community culture for disaster preparedness.
Sutopo cited data from the United Nations which stated that preparedness has more influence in suppressing tsunami casualties than infrastructure. People must be aware the need to build shelters and to meet the local Spatial and Regional Plan (RTRW) by not building permanent buildings on the shoreline.
"So our biggest challenge is in the downstream part, that is in the part of community preparedness facing disasters. Components are three-fourths of the total tsunami early warning system. Equipment such as sensors or buoys, only a fourth," he said.
Immediately after the Sunda Strait tsunami, President Joko Widodo instructed the BMKG to purchase tools for early detection of tsunamis caused by volcanic eruptions, especially in the area around Anak Krakatoa. The BMKG also began installing sensors to monitor wave height around the Sunda Strait.
Meanwhile, post-disaster reconstruction continues. PUPR Minister Basuki said the government is remapping earthquake-prone areas in Palu to prohibit building in sensitive areas. After the study was completed, the government will begin building a "New Palu.” The ministry is targeting the construction to begin this year and to be completed by 2021. The government will build at least 14,400 houses and supporting infrastructure at a cost estimated at Rp.18 trillion.