BANDUNG, itb.ac.id – Dr. Heri Andreas, S.T., M.T, a lecturer from Faculty of Earth Sciences and Technology ITB said that land subsidence is one of main factors of Jakarta floods that happened every year. The capital city of Indonesia, Jakarta is sinking by an average of 1-10 cm a year and almost half the city now sits below sea level.

"If an area is sinking because of land subsidence, there will be a basin and it will cause flooding," said Heri, a member of Geodesy Research Group, Sunday (01/05/2020).

He said, there were several factors that can cause land subsidence; natural compaction, groundwater extraction, heavy load from big buildings and houses, tectonic factors, and exploitation of oil, gas, and subsurface mining. "In Jakarta, the most dominant factors are groundwater extraction and heavy load from above," he said.

He explained, many technologies have been implemented to reduce land subsidence in the world, especially in developed countries. For example, by groundwater substitution with surface water, water recycling technology, wastewater treatment, and injection of seawater into the ground. "In Indonesia, those technologies has not been massively implemented by our government," he added.

He continued, land subsidence can be measured through satellites or GPS with high accuracy up to millimetres. However, humans may not notice it because it happens slowly. The government should have a database of land subsidence in their area so they can implement good policies to anticipate land subsidence and floods.

According to Heri, the best solution of Jakarta floods must be studied from various aspects. The source of flood should be predicted so the government can prepare and take some right actions to face it. "Flash floods that occurred throughout Jakarta on 1 January 2020 were caused by extreme heavy rain," he added.

Meanwhile, volume or capacity of rivers, reservoirs, and retention ponds were not enough to accommodate rain water. Therefore, river normalization and naturalization should be done by DKI Jakarta Provincial Government to increase those capacities. “Relocation of residents who lives on the riverbanks is a difficult thing to do. They already lived that way for long, "he said.

According to Heri, land subsidence will not happen at North Bandung such as Dago, Lembang and its surroundings because those areas were formed by hard rocks. However, the potential of natural damage are generated by forest conversion into housing or settlements. Meanwhile, South Bandung is facing land subsidence started from downtown area to the south.

Reporter: Adi Permana
Translator: Billy Akbar Prabowo