Disasters in Sumatra: Cyclone Accumulation and Environmental Conditions

MAKASSAR, KOMPAS—The disasters occurring in North Sumatra, West Sumatra, and Aceh are the result of the accumulation of tropical cyclone Senyar and environmental conditions. The incidents are similar to the flash floods that previously claimed 38 lives in South Sulawesi.

This was stated by the Head of the Center for Disaster Studies at Hasanuddin University, Ilham Alimuddin, in response to the disaster on Sumatra Island, Friday (28/11/2025).

"There is an influence of a cyclone moving from Thailand to Malaysia and then to the Sumatra region. This is not a local disaster standing alone but a series of global disasters that shift from one place to another. However, environmental conditions exacerbate this disaster," he said in Makassar, Friday (28/11/2025).

He stated that the cyclone causing heavy rainfall is merely a trigger. However, if the cover or vegetation is already diminished and exacerbated by the narrowing and shallowing of water flows or rivers, then materials will be easily carried away.

"Imagine if a cyclone strikes down, then the rainfall is very high and the surface barriers are already insufficient, causing soil, rock, and wood materials to be easily swept away. This is exacerbated by the condition of rivers that can no longer accommodate the volume of water," he said.

The elevation from upstream to downstream significantly affects the speed and force of the water flow. This causes a large amount of material to be easily carried away and to strike the villages along the river's course down to the downstream.

"All this time, although forest cover has decreased, if it does not rain, nothing happens. When it rains, especially with high intensity, only then does the surface get washed away. Conversely, even if the volume of rain is large, if there is still vegetation to hold it back, even if the water overflows, the condition will not be severe," he said.

Ilham stated that the flash floods in West Sumatra and North Sumatra are similar to those that occurred in Masamba, the capital of North Luwu, South Sulawesi, in 2020. At that time, the flash floods claimed the lives of 38 people and left more than 10 others missing.

"In Masamba, a landslide occurred upstream due to the fragile rock structure, and as a result, the landslide material was carried away by the water and swept along the river and downstream. The difference in Sumatra is that the water appears murkier and brownish. This indicates that the amount of mud material carried from upstream is significantly greater," he said.

Regarding the disaster in Sumatra, the National Search and Rescue Agency or Basarnas reported that as of Friday (28/11/2015) afternoon, 105 people have died.

The number includes details from North Sumatra, where 83 people have been reported dead and 81 others are still missing. The highest number of fatalities occurred in Central Tapanuli, with 34 individuals, and in Sibolga, with 30 individuals. Additionally, a total of 677 people have been successfully evacuated.

In West Sumatra, 22 people have been reported dead and 12 others are still missing. Data from the Padang Search and Rescue Office indicates that the highest number of fatalities occurred in Agam, with 10 individuals. The total number of residents evacuated has reached 29,152 people.

In Aceh, the number of dead and missing victims is still being recorded. According to data from the Banda Aceh Search and Rescue team, a total of 645 people have been evacuated. The highest number of refugees is in North Aceh, with 3,507 people, and in East Aceh, with 2,456 people.

The Head of Basarnas, Mohammad Syafii, stated that the search for missing victims and the evacuation of residents are ongoing. Various equipment is being utilized, including helicopters, excavators, rubber boats, and monitoring drones. So far, approximately 2,000 personnel have been deployed for the disaster evacuation process.