Bali Floods: Not Just a Result of Global Warming, Moral Factors Too

JAKARTA – Heavy rain has continued to pound Bali since Tuesday (September 9, 2025). Flooding has affected most of Bali, with dozens of people reportedly dying.

The National Disaster Management Agency (BNPB) is monitoring the flooding in four administrative areas of cities and regencies in Bali Province. The affected areas are Jembrana, Gianyar, Tabanan, Klungkung, and Denpasar Regencies.

The flooding, triggered by extreme rain, occurred at the peak of the dry season, signaling increasingly unpredictable weather conditions due to global warming.

I Gede Agung Teja Bhusana Yadnya, Head of the Bali Regional Disaster Management Agency (BPBD), stated that this was the worst flooding in a decade. In addition to heavy rainfall, Teja also highlighted that development issues could be a contributing factor to the massive flooding in Bali.

"This development is an infrastructure issue. The water network infrastructure must be good, and river flows are also disrupted by the impact of the development," he said.

Triggered by Equatorial Rossby Waves

Siswanto, a climate researcher at the Meteorology, Climatology, and Geophysics Agency (BMKG), stated that August and September should be the peak of the dry season in most of East Nusa Tenggara (NTT) and Bali.

"Flooding at the peak of the dry season in Bali and NTT like this is the first time it has happened," he said.

Siswanto added that regionally, the heavy rain that triggered the flooding was triggered by the activation of Equatorial Rossby Waves. This triggered fairly widespread heavy rains from Bali to Nusa Tenggara and southwest Kalimantan.

The Equatorial Rossby Wave phenomenon is a type of atmospheric disturbance that significantly influences weather patterns in tropical regions, including Indonesia.

These waves are named after Carl-Gustaf Rossby, the scientist who first identified them in the 1930s. The main characteristic of Equatorial Rossby Waves is their east-west movement along the equator at a relatively slow speed, ranging from 5-10 meters per second.

These waves typically last 10-20 days. When active, they can cause wind instability in the lower atmosphere and encourage the accumulation of moist air masses from tropical sea areas such as the Indian Ocean and the Java Sea.

According to several studies, the impact of Equatorial Rossby Waves on weather is that they often trigger the growth of intense convective clouds that cause heavy rainfall and extreme weather, including the recent events in Bali.

Improper Spatial Planning

The recent heavy rains in Bali were unavoidable. However, severe flooding could have been minimized if the city's drainage system had been working properly. Unfortunately, Bali, like other major cities, has faced a number of problems in recent years.

One factor exacerbating the flooding is improper spatial planning. Uncontrolled land conversion in Bali, including in Denpasar, has narrowed water catchment areas.

Putu Rumawan Salain, a spatial planning observer from Udayana University, stated that development along riverbanks, such as the Ayung River, actually shifts the flood risk to other areas. He called it a phenomenon of "throwing the flood to the neighbor" because natural water channels are being lost due to residential development.

Rumawan emphasized that Bali currently needs to normalize several rivers that are prone to overflowing and causing flooding. Furthermore, the local government must also develop flood mitigation technology so that significant river levels can be monitored digitally. He said this is already being implemented in major cities in Indonesia.

He further emphasized that every city should maintain 30 percent green open space (RTH). However, in Bali, only around 15–20 percent of RTH remains. This lack of infiltration space causes rainwater to directly become surface runoff, increasing flooding.

Rumawan observed that the implementation of spatial planning regulations in Bali has become inconsistent. Numerous spatial planning violations have emerged, especially in Denpasar and the surrounding areas, resulting in increasingly limited green open space.

"The ratio of land use for buildings to undeveloped land has increased. It's likely already above 60 percent," Rumawan said.

Ignoring Ancestral Messages

The flooding phenomenon in Bali has also attracted the attention of cultural academics. I Gede Sutarya, Professor of Planning and Development of Spiritual and Religious Tourism at I Gusti Bagus Sugriwa State Hindu University (UHN), believes that flooding should not have occurred in Bali, which has long been known for its water management system. He alluded to ancestral heritage recorded in the palm-leaf manuscripts (lontar), emphasizing the balance in maintaining river flows and their boundaries.

In Balinese palm-leaf manuscripts, Bagus explains that areas near rivers should not be used for buildings, let alone settlements. Even wood from riverbanks should not be taken for construction.

"This disaster poses a moral question for us as Balinese. Are we truly practicing Balinese culture?" he asserted.

He emphasized that the answer should not simply be a regional regulation or circular, but rather concrete action to regulate buildings along riverbanks and widen waterways.

Similarly, Sugi Lanus, a cultural expert and reader of Balinese and Old Javanese palm-leaf manuscripts, stated that the flooding was evidence that the customary rule, "perarem telajakan-teba," prohibiting building on riverbanks or in front of houses, was being ignored.

He explained that the palm-leaf manuscripts strictly prohibit building in the Karang Tenget, Karang Suwung, Telajakan, Hulun Pangkung, and Rejeng Tukad areas. These rules stem from the traumatic experiences of ancestors and are written in mythical and mystical language.

However, because they cover myths and mysticism, the narratives in lontar palm-leaf manuscripts seem neither scientific nor historical, considered merely superstition. Nevertheless, lontar palm-leaf manuscripts actually contain historical data on spatial planning and disaster mitigation.

Riverbanks and riverbanks are crucial buffer zones that must be free of buildings to ensure the smooth flow of water, preventing environmental damage and potential loss of life and property.

For these two figures, the flooding that hit Bali was not just a natural issue, but also a cultural and moral one. When ancestral rules are ignored, disaster becomes the real answer to that negligence.