Hydrometeorological Disaster Hits Sumatra: What Mitigation Measures Should Be Taken?

1. What triggered a series of hydrometeorological disasters in a number of areas in Sumatra?

The incessant rain since mid-November marked the beginning of a series of hydrometeorological disasters in Aceh, North Sumatra, and West Sumatra. Behind this extreme rainfall, there is one main trigger, namely the tropical cyclone seed 95B that formed in the Malacca Strait. Within a matter of days, this seed intensified and officially attained the status of Tropical Cyclone Senyar, a phenomenon that rarely occurs in regions near the equator.

The head of BMKG, Teuku Faisal Fathani, stated that Senyar is an unusual system. "This system has intensified and is officially classified as Tropical Cyclone Senyar. Its presence increases the supply of water vapor in the Malacca Strait and triggers very heavy rainfall," he said.

The movement of the cyclone that made landfall in Aceh, instead of weakening over the sea, has drastically changed the weather conditions in a short period of time.

Warmer than usual sea surface temperatures are serving as additional fuel. BMKG climate researcher, Siswanto, explained that the Malacca Strait is in an unusual situation. "The sea conditions are relatively warm, higher than the climatological average, thus providing latent energy for the growth of tropical systems," he said.

It is this latent energy that sustains large convective clouds and makes extreme rainfall persist for days.

Extreme rainfall is not only triggered by cyclones. At the same time, the western region of Indonesia is in a negative phase of the Indian Ocean Dipole (IOD), which causes more water vapor from the Indian Ocean to be drawn into the atmosphere of Indonesia. This combination results in an increase in rainfall intensity beyond the normal seasonal patterns.

Topography also exacerbates the situation. The steep mountains and unstable soil in Tapanuli, Aceh, and West Sumatra cause the area to become quickly saturated with water. When it rains continuously, the fragile slopes can no longer bear the load. Landslides occur simultaneously at many points, burying national roads and severing intercity connections.

2. What were the impacts and how many victims were there from the hydrometeorological disaster in Sumatra?

The impact of the disaster is most severe in North Sumatra. At least 25 people have died due to flash floods and landslides that struck the Tapanuli region, Sibolga, and its surroundings. Landslide debris has blocked roads, trapping residents and cutting off logistics. In several villages, residents must walk to higher ground while carrying whatever belongings they can.

In Padang, flash floods claimed the lives of five individuals. They were residents living along the banks of the Lubuk Minturun River, whose homes were swept away by the current and buried under flood debris. Fajar, one of the residents of the Luminpark Cluster, recounted that the flood arrived in just a matter of minutes. "The water mixed with mud rose to waist height. We only had time to save ourselves on the second floor," he said.

In Agam, a flash flood struck the village of Malalak Timur. Two residents were found dead, while one person is still missing. The debris from the flash flood, consisting of mud, stones, and tree trunks, struck houses and blocked the main road. Four evacuation points were opened, but three of them are difficult to reach due to a broken bridge.

Aceh recorded the most extensive impact. A total of 46,893 residents were affected, with nearly 1,500 people displaced. Flooding in Lhokseumawe, North Aceh, Langsa, and Bireuen submerged thousands of homes up to 1 meter high. National roads in several areas turned into rivers, and thousands of vehicles were trapped.

In addition to loss of life and physical damage, this disaster has paralyzed basic services. Thousands of homes lost electricity due to the collapse of the SUTT tower. Telecommunications networks were disrupted at several points, particularly in Central Tapanuli. Educational and health facilities were also submerged, causing community activities to come to a complete halt.

Severe flooding has also been recorded in Malaysia and Thailand due to the subsequent effects of cyclone movement. This underscores that the Senyar phenomenon is a meteorological event of regional scale, not merely local.

Economic losses are estimated to reach hundreds of billions of rupiah, primarily due to damage to infrastructure, residential homes, agricultural land, and electrical networks. However, social impacts such as the loss of family members and trauma experienced by victims, including the loss of shelter, cannot be quantified in numerical terms.

3. How are hydrometeorological disasters handled in Sumatra?

Since the beginning of the disaster, all elements of the government have acted swiftly. In North Sumatra, the disrupted road access has become the biggest challenge. A major landslide has buried the Tarutung–Sibolga route, preventing logistics trucks and rescue vehicles from passing through. The Regional Disaster Management Agency has deployed heavy equipment, but the ongoing rain and shifting soil have prolonged the cleanup process.

A joint team from the BPBD, Basarnas, TNI, and the police is working day and night. A BPBD officer in Padang Sidimpuan described the situation. "We are having difficulty accessing the area. Landslides have blocked the entire road. Many residents are isolated, and we are trying to reach them through alternative routes that are also hazardous," he said.

In Aceh, floods have affected nine districts/cities. Evacuations are being carried out using rubber boats, especially for the elderly, pregnant women, and children. The Acting Head of BPBA, Fadmi Ridwan, stated that emergency coordination is being conducted intensively. "BPBA continues to coordinate with BPBD. Our focus is on saving residents and ensuring that basic needs are met," he said.

The heavy rainfall also caused the collapse of five 150 kV transmission towers in Bireuen. PLN Aceh Communication Manager Lukman Hakim described the damage as one of the largest in recent years. "We are deploying hundreds of personnel and heavy equipment to restore the network. The conditions are challenging, but electricity must be restored," he said.

The Ministry of Social Affairs also sent assistance amounting to IDR 2.6 billion in the form of tents, mattresses, ready-to-eat meals, and family supply packages. Field kitchens were opened to serve thousands of survivors. Social workers collaborated with volunteers and local residents to ensure fair distribution.

In West Sumatra, Basarnas deployed a team to scour the locations of the flash floods in Lubuk Minturun and Kampung Apa. Large wooden debris hampered the evacuation process.

At the same time, the Meteorology, Climatology, and Geophysics Agency (BMKG) updates its early warning every few hours. The head of BMKG, Teuku Faisal Fathani, emphasized that this information should serve as a basis for prompt action to prevent disasters from occurring.

4. What mitigation measures need to be taken to prevent a recurrence of hydrometeorological disasters in Sumatra?

The greatest lesson from this series of disasters is the urgent need to strengthen the mitigation system. The Meteorology, Climatology, and Geophysics Agency (BMKG) emphasizes that extreme weather like this will occur more frequently due to climate change. "Phenomena like Senyar may be rare, but it is not impossible for them to recur. Preparedness is key," said BMKG Meteorology Director Andri Ramdhani.

The first step is to enhance the utilization of early warnings. Local governments must ensure that every warning is followed by concrete actions—closure of landslide-prone routes, early evacuation, and preparation of evacuation posts—before the situation worsens. In many cases, residents are trapped because preventive measures are not implemented quickly enough.

Spatial planning also needs to be improved. Settlements along riverbanks such as Lubuk Minturun, areas upstream without green belts, and steep slope regions must be re-evaluated. Long-term relocation may be the only way to prevent recurring casualties.

Rehabilitation and conservation of river basin areas (DAS) need to be restored. Rivers that have narrowed and experienced sedimentation require dredging, bank reinforcement, and the construction of sabo dams to hold back materials from upstream. Supervision of construction in the upstream areas must be tightened to ensure stable water flow.

Basic infrastructure must adapt to new weather patterns. Power towers, national roads, and bridges must be designed to withstand extreme rainfall, which is now occurring more frequently. The collapse of five power towers in Aceh serves as an example of why more adaptive designs are essential.

The capacity of the Regional Disaster Management Agency (BPBD) and Search and Rescue (SAR) teams must be enhanced. The disaster in Agam, West Sumatra, illustrates how the limitations of equipment in difficult terrain can slow down evacuation efforts. Regular training, the addition of rubber boats, heavy equipment, and online evacuation routes need to be prioritized.