Palu Grows without Paying Attention to its Carrying Capacity

AHMAD ARIF

· 6 minutes read

The government has long known the vulnerability of Palu city, Central Sulawesi, to earthquakes, tsunamis and soil liquefaction. However, this city was allowed to grow without control with the majority of the population not knowing the disaster history in their city.

The vulnerability of Palu city to earthquakes and tsunamis was repeatedly disclosed by JA Katili, the first doctoral graduate in geology from the Bandung Institute of Technology and also in Indonesia in the 1970s. Katili also named this fault as Palu Koro because it extends from Palu Bay in the north to Koro around Tondano Bay, North Sulawesi, for about 1,000 kilometers.

When he served as Director General of General Mining in the 1973-1984 period, Katili initiated the establishment of the National Earthquake Work Agency. His reason at that time was that many areas in Indonesia were vulnerable to earthquakes and tsunamis, but the study on it was limited. One of the sources of the earthquake that Katili feared was Palu city (Kompas, 20 July 1976).

In his biography book, Harta Bumi Indonesia (The Earth Treasure of Indonesia) (2007), Katili said, "It is understandable if people living in Palu city are afraid of the threat of tsunami. Because, the city is located on the tip of the fault and in a pulling basin as well."

Katili questioned why the government at that time chose Palu as the capital city of Central Sulawesi Province in 1964. However, his knowledge about the vulnerability of the disaster in Palu city could not prevent the central government\'s decision from making Palu city an administrative city in 1978.

Albertus Christiaan Kruyt and Nicolaus Andirani in their book (1912) wrote, Palu is a "New City" located at an estuary. Even though the Kingdom of Palu is said to have existed since 1796, but until the colonial era, the City of Palu had not yet developed. The Dutch chose to make Donggala as the Central Sulawesi Afdeling center.

"Initially, the Kaili people who were the first inhabitants of this region chose to live in the highlands around the Palu valley," said Iksam, the archaeologist who is also the Deputy Head of the Central Sulawesi Regional Museum.

One of the reasons that local residents chose to live in the highlands was probably fear for the repetition of the tsunami in the past. It gave birth to the term bombatalu or three devastating sea waves.

The high frequency of the tsunami was emphasized by a study by Gegar Prasetya (2001), which recorded that the Makassar Strait, including Palu Bay, had been hit by the tsunami up to 18 times since the 1800s. That is the most frequent event in Indonesia.

Compared to previous events, the height of the tsunami that hit Palu this time was relatively smaller. For example, in 1927, an earthquake measuring M 6.3 triggered a tsunami of up to 15 meters in Palu Bay. In 1968, an M 7.4 earthquake triggered a tsunami in Palu Bay up to 10 meters.

Even though the tsunamis were higher, the number of victims was smaller at that time, namely 12 people were killed in 1927 and 200 people were killed in 1968.

Compare this with the current disaster, which according to data from the National Disaster Mitigation Agency (BNPB) on Friday (05/10/2018), the dead toll had reached 1,558. The increase in the number of casualties was due to the increasing density of the population of Palu city, especially those inhabiting vulnerable areas of soil liquidation or the shift in soil due to the earthquake.

According to Iksam, regions that have recently experienced soil liquidation have only been inhabited after the 1970s. The Kaili people already know about this soil liquefaction, which in the local language is called nalodo or being sucked in the mud. The rapid population growth in Palu city makes areas that were traditionally avoided but then used as housing complexes. Moreover, Palu also becomes a magnet that draws residents from a number of other regions who have no memory about the disasters in this city.

Risks vs growth

From the aspect of the earthquake and tsunami, the vulnerability of Palu city has also been included in Peta Sumber dan Bahaya Gempa Indonesia (the Map of Sources and Danger of Indonesian Earthquakes) Map compiled by the National Earthquake Study Center. The map was then launched by the Ministry of Public Works and Public Housing in September 2017.

The vulnerability of Palu\'s soil liquefaction has also been mapped. The research report about the potential of Palu\'s soil liquefaction by Risna Widyaningrum from the Geological Agency, Ministry of Energy and Mineral Resources, in 2012 concluded that the majority of the city area has a very high potential of soil liquefaction due to the weak carrying capacity of the land, in addition to the closeness to the fault line.

Among the areas that are very susceptible to soil liquefaction, which have been identified, include Petobo. As has been known, Petobo was among the areas which were most severely affected by the soil liquefaction and resulted in disappearance of 744 homes.

According to Secretary of the Geology Agency of the Ministry of Energy and Mineral Resources Radmono Purbo, the soil liquefaction study in Palu city was carried out after learning from the effects of soil liquefaction due to the earthquake that occurred in Padang Pariaman, West Sumatra, which buried 400 people in 2009. "After that we mapped soil liquefaction in several cities, including Palu. I am sure that the results of this study have been submitted to the regional governments to be considered in development," he said.

However, until the earthquake occurred, the majority of the population of Palu city are believed not to be exposed to information on the vulnerability of their city. "So far studies on the risks and vulnerabilities of disasters in an area tend to be ignored and not opened because they are considered to affect investment," said the Head of the Center for Natural Disaster Studies, Gadjah Mada University, Yogyakarta, Djati Mardianto.

In fact, the regional spatial plan (RTRW) should be a control to reduce the impact of disasters if its implementation takes into account risk assessment. "The problem is that the RTRW is mostly only economically oriented. A number of new infrastructure, such as Yogyakarta Airport, were built in earthquake and tsunami prone areas, in addition to flooding," he said.

In addition to Yogyakarta Airport, currently there are 16 other airports in Indonesia that are mapped in tsunami prone zones (Kompas, June 16, 2014).

Learning from this incident, the rebuilding of Palu city must take into account disaster risks. Moreover, the earthquake is a continuous cycle. Not only for Palu, it should be a lesson for other cities that mostly grow by ignoring the carrying capacity of the environment, while the citizens are not knowledgeable about the vulnerability of their residences. (AHMAD ARIF)

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