Floods, Forest and Land Fires, Earthquakes, and Underwater Landslides in Kalimantan (Borneo) Indonesia

South Kalimantan – The problem of the coronavirus pandemic that has hit the whole world, including Indonesia, has not yet been completed, the beginning of the new year 2021 was shocked by a series of natural disasters and disasters in Indonesia. One of them is the occurrence of flash floods in some areas on the island of Kalimantan, more precisely in South Kalimantan.

Floods

Reporting from the official website of the BNPB (Indonesian National Board for Disaster Management) on Sunday (17/01/21), this massive flood hit at least ten districts or cities such as:

1. Kota Banjarmasin
2. Banjar Baru
3. Tanah Laut
4. Kabupaten Banjar
5. Balangan
6. Batola
7. Tabalong
8. Tapin
9. Hulu Sungai Tengah
10. Hulu Sungai Selatan. 

It was recorded that around 24,379 houses were flooded, and 39,549 of them were forced to flee. Sadly, around 15 people died, with details of 7 people from Tanah Laut Regency, 3 people from Hulu Sungai Tengah Regency, and one person each from Banjar Baru City, Banjar Regency and Tapin Regency.

Seeing the impact of the floods that hit South Kalimantan this time, based on the results of monitoring by the Meteorology, Climatology and Geophysics Agency (BMKG), BNPB asked the public to remain alert because Indonesia is still hit by the rainy season until next February. It is hoped that the public will also continue to monitor weather forecast information through the BMKG website.

The occurrence of flash floods in South Kalimantan at the beginning of the new year 2021 has indeed surprised many people. It raises a lot of speculation and assumptions from various circles about what is actually the main cause of the flood. The Indonesian Institute of Sciences (LIPI), on its official website (05/12/08), once revealed that one of the causes of flooding is the annual reduction in forest cover caused by high rates of deforestation. This reduction causes the emergence of critical land in forest areas and outside forest areas of up to millions of hectares. The conversion of land functions for plantations and agriculture in several provinces on the island of Kalimantan which is carried out by means of forest exploitation such as illegal logging and encroachment as well as massive and open mining, has reduced the number of water catchment areas that can absorb rainwater.

This statement is further strengthened by several research journals published by several researchers at the Center of International Forestry Organization (CIFOR). As reported on its official website (04/12/12), CIFOR explained that of course in a large country like Indonesia, exchanging critical land for forest and peat areas to reduce deforestation is indeed very difficult to do.

Meanwhile, President Jokowi at the CAS 2021 Coalition Ambition Summit event on Monday night (25/01/21) stated that the many natural disasters that occur in Indonesia are closely related to hydrometeorology that is affected by climate change. In line with the president, the Minister of Environment and Forestry (LHK), Siti Nurbaya, as reported on the official website of the KLHK emphasized that the Indonesian government took the initiative to increase resilience to climate change that was happening and create innovations that could improve people’s welfare by collaborating. with several institutions and related parties such as ITPC, CIFOR, FAO, UNEP, COBSEA, and others.

Considering that the area of ​​forest cover is decreasing over time, our memory is certainly focused on another disaster that very often occurs on the island of Kalimantan, namely forest and land fires or karhutla (Indonesian terminology).

Forest and Land Fires

Based on data from the National Disaster Management Agency (BNPB) as explained on its official website on Monday (12/30/19), there are approximately 942,484 hectares of the total area affected by forest and land fires. This number increased compared to the previous 2017 and 2018. Furthermore, based on World Bank data, the Head of the BNPB Data and Information Center, Agus Wibowo noted that the economic losses suffered by Indonesia had reached 75 trillion rupiah because of the disaster. The number is fantastic considering that almost the entire island of Borneo has the same problem. And sadly, nearly 80 percent of the burned area of ​​Kalimantan has always been turned into land for oil palm plantations and other industrial crops.

Furthermore, from the results of satellite monitoring of the National Aeronautics and Space Agency (LAPAN) from 1 January 2020 to 31 October 2020, there were at least 564 hotspots in West Kalimantan, 91 hotspots in North Kalimantan, 120 hotspots in South Kalimantan, 142 hotspots in Central Kalimantan, and 299 hotspots in East Kalimantan.

It is estimated that the actions of some communities who are reckless to burn post-harvest land have triggered the emergence of the hotspots in question, especially if there are idle lands that are not functioning. This is also reinforced by BMKG data regarding the level of burnability of the top layer on the soil surface of each island in Indonesia, especially on the island of Kalimantan as shown in Figure 2 above.

To prevent more forest and land fires, BNPB together with the Ministry of Environment and Forestry (KLHK) and the Peat Restoration Agency continue to encourage approaches to empowering the wider community by involving all related parties. Some of them are BPBD, BMKG and LAPAN as well as local governments at the city, district, and provincial levels to continue to be alert in preventing and overcoming the problem of forest and land fires.

Earthquakes

Other disasters besides floods and forest and land fires that should not be underestimated are earthquakes. Sourced from the earthquake catalog data from the Meteorology, Climatology and Geophysics Agency (BMKG), the island of Borneo has also experienced eight devastating earthquakes. Although in his statement on the official BMKG website (24/08/19), Dwikorita Karnawati as the head of the agency said that the island of Kalimantan is the only island in Indonesia that has a relatively lower level of earthquake activity compared to other islands, for example, Sulawesi Island and Java, but of course the history of earthquakes in the land of Borneo cannot be underestimated no matter how small the intensity.

1. The first earthquake was recorded on May 14, 1921 in Sangkulirang, East Kalimantan. Apart from being able to trigger a tsunami, this earthquake also caused a lot of moderate to severe damage to buildings and houses.
2. Two years later, on April 19, 1923, another earthquake occurred in Tarakan, East Kalimantan. With a magnitude of up to 7.0, this one earthquake caused many fractures in the ground.
3. Similar damage was also experienced by the city of Tarakan, two years later, namely on February 14, 1925. On the scale of the intensity of shocks from VI to VII MMI, this earthquake also severely damaged many houses.
4. Two further earthquakes occurred on February 28, 1936 and October 26, 1957 in the same area with magnitudes of 6.5 and 6.1, respectively.
5. Then on February 5, 2008, an earthquake measuring 5.8 magnitude struck several islands at once in Kalimantan, for example, Sebuku Island, Batulicin, Sembilan, Pagatan, and Pulau Laut.
6. The next three earthquakes occurred in different areas on the island of Kalimantan, for example, the Tarakan earthquake on December 21, 2015
7. Earthquake in Kendawangan, West Kalimantan on June 24, 2016
8. And in Katingan, Central Kalimantan on July 14 2018 with a shock scale of up to 4.2 magnitude. Although the intensity is only on the MMI III to IV scale, this earthquake shock can be felt in other areas around it such as Kasongan, Bengkuang, and Batutinggi.

Although it is considered seismically “safer” compared to other islands, BMKG still prepares socialization activities for the community such as self-evacuation education and evacuation training in earthquake-prone areas in Kalimantan, especially in tsunami-prone coastal areas. Together with stakeholders and several related institutions such as BNPB and BPBD, BMKG is preparing an earthquake monitoring system as well as more capable earthquake and tsunami mitigation efforts.

Of course, these efforts are very important to do and apply considering that from the geological tectonic map itself, it turns out that there are five earthquake faults or faults that pass through the island of Borneo. The five faults are:

1. Tarakan and Sampurna Faults in Nunukan, North Kalimantan
2. Meratus Fault in South Kalimantan
3. Maratua Fault that passes through East to North Kalimantan
4. Sampurna Fault in the Nunukan area, North Kalimantan
5. The Adang Fault, which is a long and large regional fault that divides the island of Kalimantan into South and North Kalimantan.

These faults undoubtedly make the people of the island of Kalimantan be aware of the occurrence of aftershocks in the future.

Underwater Landslides

Apart from earthquakes, floods, and forest and land fires, a research team consisting of scientists from the UK and Indonesia also found underwater landslides in the Makassar Strait, which borders the islands of Kalimantan and Sulawesi. In their research publication entitled “Indonesian Throughflow as a Preconditioning Mechanism for Submarine Landslides in The Makassar Strait,” Dr. Uisdean Nicholson and other researchers stated that the landslide phenomenon can increase the potential risk of a tsunami in the future. This is based on the results of seismic data and sedimentary structures on the Makassar seabed.

The survey results show that there are 19 vulnerable zones along the strait. The research team suspects that the occurrence of landslides on the seabed or Mass-Transport Deposits (MTD) was triggered by sediments that had accumulated and were carried by strait currents and then buried on the shallow and deeper seabed. Because the ocean currents do not stop, the pile becomes unstable and collapses.

Based on the frequency of the slope collapse and the strait rock samples that had been extracted, the researchers were also able to determine how old the sediments had accumulated over a long period of time. So, it can be said that a tsunami does not only occur due to a megathrust earthquake like the one that occurred in Aceh in 2004, but can also arise because of the landslide of sediment that has accumulated on the seabed like the one in the Makassar Strait. A more complete explanation of the seabed study that has been carried out by these researchers can be seen in person in the collection of the journal Geological Society of London published on April 1, 2020.