In late November 2025, rare tropical Cyclone Senyar dumped extreme rainfall on Indonesia's Sumatra island, unleashing catastrophic floods and landslides across the provinces of Aceh, North Sumatra and West Sumatra. By January 4, 2026, Indonesian authorities reported at least 1,177 deaths and 165 missing, with more than 3.3 million residents affected and around 1.1 million displaced across 52 cities and regencies. Economic losses exceeded 68.7 trillion rupiah ($4.13 billion), with 166,743 houses damaged along with hundreds of bridges, health facilities and schools. The same storm systems killed roughly 200 more people in southern Thailand and Malaysia, turning a regional weather anomaly into Southeast Asia's deadliest climate disaster of the year.
As survivors struggle through debris-choked valleys and 450,000 people remain unable to return home a month later, attention has shifted from the storm itself to what made it so deadly. Environmental groups and local communities point to years of deforestation, mining, logging, palm oil expansion and large infrastructure projects in the Batang Toru and other river basins—Sumatra lost 4.4 million hectares of forest between 2001 and 2024—arguing that these activities stripped hillsides of forest, accelerated erosion and turned heavy rain into lethal flash floods. In response, Jakarta revoked 22 forestry permits encompassing over one million hectares on December 15, suspended operations of four companies in the Batang Toru basin, and continues to investigate violations. Yet President Prabowo Subianto has refused to declare a national disaster despite pressure from 113 civil society organizations, insisting existing regional arrangements are sufficient—a stance critics say reflects Jakarta's slow, inadequate response and reluctance to confront the structural drivers of Indonesia's mounting climate vulnerability.
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Key Indicators
1,177
Confirmed deaths in Sumatra floods (as of Jan 4, 2026)
Indonesia's disaster agency BNPB reported 1,177 dead and 165 missing by January 4, 2026, making this Indonesia's deadliest natural disaster since the 2018 Sulawesi earthquake and tsunami.
165
People reported missing in Sumatra
As of early January 2026, 165 people remain missing across three Sumatran provinces, with search operations complicated by damaged infrastructure and terrain.
3.3M+
Residents directly affected
BNPB estimates that more than 3.3 million people have been affected and around 1.1 million displaced across 52 cities and regencies in Aceh, North Sumatra, and West Sumatra.
4.4M ha
Forest lost in Sumatra since 2001
Satellite-based analyses cited by environmental groups and Reuters indicate that Sumatra has lost about 4.4 million hectares of forest between 2001 and 2024—an area larger than Switzerland—driven largely by logging, mining and plantation expansion.
22
Forestry permits revoked nationwide
On December 15, 2025, the Indonesian government revoked 22 forestry permits covering over one million hectares across the country, including more than 100,000 hectares on Sumatra, in direct response to the floods.
$4.13B
Estimated economic losses
Government assessments estimate economic losses from Cyclone Senyar-induced floods exceed 68.7 trillion rupiah ($4.13 billion), including damage to 166,743 houses, 734 bridges, and critical infrastructure.
People Involved
Prabowo Subianto
President of Indonesia (Refused to declare national disaster despite rising death toll and pressure from 113 civil society organizations; vowed normalcy within 2-3 months)
Raja Juli Antoni
Forestry Minister of Indonesia (Leading investigations into logs and corporate responsibility for floods)
Hanif Faisol Nurofiq
Environment Minister of Indonesia (Confirmed suspension of four companies in Batang Toru watershed; overseeing environmental audits)
Bahlil Lahadalia
Minister of Investment / Energy-related policymaker (Signalled willingness to revoke mining permits tied to environmental violations)
Suharyanto
Head of Indonesia’s National Disaster Management Agency (BNPB) (Coordinating casualty data and national disaster response operations)
Rianda Purba
Executive Director, WALHI North Sumatra (Leading NGO accusations against seven companies over ecological damage)
Organizations Involved
GO
Government of Indonesia
National Government
Status: Coordinating national disaster response and environmental enforcement actions
The central government of the Republic of Indonesia, responsible for national disaster policy, environmental regulation and coordination with provincial authorities.
NA
National Disaster Management Agency (BNPB)
Government Body
Status: Primary coordinator of disaster response and data in Sumatra
Indonesia’s BNPB is the central agency responsible for disaster risk reduction, emergency response and coordination with provincial disaster offices.
WA
Wahana Lingkungan Hidup Indonesia (WALHI)
Environmental NGO
Status: Leading critic of corporate and state roles in deforestation-linked disasters
WALHI, Friends of the Earth Indonesia, is the country’s largest environmental network, active on issues from deforestation and mining to climate justice.
MI
Mining Advocacy Network (JATAM)
Non-Governmental Organization
Status: Providing data on mining-linked deforestation and hydropower risks
JATAM is an Indonesian network focusing on the social and environmental impacts of mining and energy projects.
PT
PT North Sumatra Hydro Energy (NSHE)
Corporation
Status: Operations formally suspended on December 10, 2025; undergoing environmental audit with PT Agincourt Resources and PTPN III
NSHE is the consortium developing the controversial Batang Toru hydropower plant in North Sumatra, a project linked to China’s Belt and Road Initiative.
Timeline
Death toll reaches 1,177 as BNPB updates final casualty figures
Disaster Impact
Indonesia's National Disaster Management Agency reports the death toll from hydrometeorological disasters across Sumatra has reached 1,177, with 165 still missing, making this the country's deadliest natural disaster since the 2018 Sulawesi earthquake and tsunami.
One month after landfall, 450,000 still displaced
Disaster Impact
A month after Cyclone Senyar struck, more than 450,000 people remain unable to return to their homes in Aceh, struggling to access clean water, food, electricity and medical supplies. Volunteers and aid workers criticize the central government's response as slow and ineffective.
President confirms death toll exceeds 1,000; vows return to normalcy in 2-3 months
Government Action
President Prabowo Subianto acknowledges the death toll has surpassed 1,000 and states he expects flood-stricken Sumatra to return to normal conditions within 2-3 months as recovery efforts intensify.
Government revokes 22 forestry permits covering 1 million hectares
Government Action
In a landmark enforcement action, Indonesia's government revokes 22 forestry permits encompassing more than one million hectares of land nationwide, with over 100,000 hectares of the cancelled permits located on Sumatra. The move represents the most significant permit revocation in response to the floods.
Coalition of 113 civil society organizations delivers legal notice demanding national disaster declaration
Public Backlash
A coalition of 113 Indonesian civil society organizations sends a formal subpoena to President Prabowo Subianto demanding he declare the Sumatra floods a national disaster, arguing that the regional emergency status is insufficient and that Jakarta's response has been too slow.
Four companies formally suspended pending environmental audits
Investigation
Environment Minister Hanif Faisol Nurofiq confirms the suspension of four companies in the Batang Toru watershed: gold miner PT Agincourt Resources, state-owned plantation firm PTPN III, hydropower developer PT North Sumatera Hydro Energy, and palm oil company PT Sago Nauli. All operations must cease while environmental audits are conducted.
Three companies summoned to Jakarta for official inspection
Investigation
PT Agincourt Resources, PTPN III, and PT North Sumatera Hydro Energy are summoned to Jakarta for formal environmental inspection as authorities examine their role in deforestation and land clearing that may have amplified flood impacts.
Prabowo refuses to declare national disaster despite rising toll
Government Action
President Prabowo Subianto states that he will not declare a national disaster, insisting that the situation remains manageable through coordinated efforts with local governments. He says: "We do not need to declare a national disaster. However, that does not mean we do not view this as a very serious matter." The decision draws criticism from disaster management experts and affected communities.
Death toll in Sumatra floods surpasses 900 as Batang Toru firms suspended
Government Action
On December 6, Indonesian authorities report that the death toll from cyclone-induced floods and landslides across three Sumatran provinces has risen to around 908–916, with 270–410 people still missing. Survivors in Aceh Tamiang recount walking for an hour over slippery logs and overturned cars to reach volunteer-run aid centres. Environmental groups continue to blame deforestation from mining, logging and infrastructure projects for worsening the disaster. The environment ministry orders all companies in the Batang Toru River Basin and nearby Garoga basin to halt operations for environmental audits, summoning three firms to Jakarta for inspection on December 8. Calls intensify for President Prabowo to declare a national disaster, but he maintains that existing arrangements are sufficient for now.
Authorities trace origin of massive log flows
Investigation
Following meetings with the national police chief, Forestry Minister Raja Juli Antoni says investigators are tracing the origin of logs swept away by floods, examining links to illegal logging, oil-palm and mining land clearing, and various land rights schemes. The statement underscores the possibility of both legal and illegal land-use practices contributing to the disaster.
Government identifies 12 suspect firms; vows action on mining permits
Investigation
Forestry Minister Raja Juli Antoni tells parliament that authorities have identified 12 companies suspected of contributing to the floods and landslides through illegal or excessive forest clearing, many in the Batang Toru region. Separately, Investment and energy officials say they will revoke mining permits for companies found in violation, while environmental watchdogs highlight some 54,000 hectares of forest converted for extraction in affected areas. BNPB updates the toll to 836 dead and 517 missing.
Prabowo orders national-level response but stops short of national disaster status
Government Action
President Prabowo Subianto instructs that the Sumatra floods and landslides be treated as a national priority, ordering ministries, the military and police to fully mobilise resources. Officials clarify that while the response is at a national level, the disaster has not yet been formally designated a "national disaster" under Indonesian law, prompting continued calls from local leaders for an upgrade to unlock additional relief funds.
Locals and officials blame ‘mischievous hands’ and deforestation
Public Backlash
In a widely cited Reuters report, residents and officials in North Sumatra describe logs littering beaches and rivers and accuse logging, mining and palm oil companies of exacerbating the disaster through rampant deforestation. Environmental groups say Sumatra has lost 4.4 million hectares of forest since 2001, and that projects like the Batang Toru hydropower plant and the Martabe gold mine have degraded ecosystems and increased landslide risk.
Batang Toru region hit by debris-laden flash floods
Disaster Impact
Flash floods in the Batang Toru area of South Tapanuli send heavy machinery and large volumes of logs downstream, with images of log-jammed rivers and destroyed infrastructure going viral and fuelling speculation about illegal logging and construction waste.
Early flood tolls in Sumatra surpass 170 dead
Disaster Impact
By November 28, Indonesia’s disaster agency reports at least 174 dead and 79 missing from flash floods and landslides on Sumatra, with North Sumatra, Aceh and West Sumatra hardest hit. Thousands of homes are submerged, roads and bridges collapse, and tens of thousands flee to temporary shelters.
WALHI North Sumatra publicly accuses seven companies—including PT Agincourt Resources, PT North Sumatra Hydro Energy and PT Toba Pulp Lestari—of deforestation, river alteration and wildlife corridor destruction in the Batang Toru basin, arguing that this ecological damage magnified the impact of Cyclone Senyar-induced floods and landslides.
Cyclone Senyar forms and makes landfall near Sumatra
Meteorological Event
Cyclonic Storm Senyar develops over the Strait of Malacca and makes landfall on northeastern Sumatra around November 25–26, bringing extreme rainfall that sets the stage for widespread floods and landslides across Aceh, North Sumatra and West Sumatra, as well as southern Thailand and Peninsular Malaysia.
Scenarios
1
Targeted sanctions and symbolic reforms, but business largely as usual
Discussed by: Analysts and reporting in Reuters, Antara and Indonesian media highlighting permit reviews but cautious about deep structural change
Under this scenario, the government maintains intense rhetoric but confines action to a limited set of highly visible companies, especially those already controversial like NSHE and Agincourt Resources. A handful of permits are suspended or revoked, some executives face administrative sanctions, and selected restoration projects are announced in Batang Toru and high-profile watersheds. However, large-scale forest clearing for plantations, mining and infrastructure continues under slightly tighter procedural rules. Prabowo’s administration frames the response as balancing economic growth with environmental responsibility, and the immediate political crisis passes once casualty figures stabilise and aid flows normalise. The underlying drivers—fragmented land governance, permissive licensing and weak enforcement—remain largely intact, making a similar disaster likely in future La Niña years.
2
Precedent-setting crackdown and legal cases reshape land-use politics
Discussed by: Environmental NGOs like WALHI and JATAM, some legal scholars and climate advocates pushing for a ‘Sumatra moment’ akin to past watershed court rulings
Here, the scale of the tragedy and clear evidence of deforestation push Prabowo’s government, courts and prosecutors into unusually forceful action. Environmental audits in Batang Toru and other basins lead to revocation of multiple mining, plantation and infrastructure permits, including for politically connected firms. Class-action or public interest lawsuits seek damages and ecosystem restoration orders, and the Constitutional Court or Supreme Court issues decisions tightening standards for Environmental Impact Assessments and disaster risk in land-use planning. Indonesia uses the crisis to bolster its climate diplomacy—highlighting loss and damage—while also tightening domestic green taxonomy rules so that hydropower and other projects in high-risk, biodiverse areas face stricter scrutiny or are cancelled. This scenario would mark a structural shift in how climate risk and cumulative impacts are integrated into permits, but requires sustained political will that has often been absent in past disasters.
3
Scapegoating a few firms while systemic deforestation quietly continues
Discussed by: Skeptical NGO voices and some independent commentators noting Indonesia’s long history of post-disaster blame without structural reform
In this outcome, investigations focus heavily on a narrow set of companies—perhaps those already unpopular or financially weak—while other powerful operators and underlying permitting practices escape serious scrutiny. A few firms in Batang Toru are punished and used as examples, but no comprehensive review of land concessions, peatland drainage, or forest-zoning policy occurs. Government narratives increasingly stress the ‘unprecedented’ nature of Cyclone Senyar and global climate change rather than domestic governance failures. Over time, public attention fades, development projects resume after cosmetic adjustments, and local communities remain exposed to similar compound risks of extreme rainfall, unstable slopes and sediment-choked rivers.
4
National disaster designation triggers broader climate adaptation push
Discussed by: Disaster management experts, some legislators and regional leaders calling for stronger central coordination and funding
If casualty numbers and humanitarian needs continue to rise, Prabowo may formally declare the Sumatra floods a national disaster. This would unlock additional budgetary and operational tools, justify large-scale relocation or rebuilding programs, and open the door to new climate adaptation finance from multilateral banks and partners. In an ambitious version of this path, the government uses post-disaster reconstruction to pilot river-basin-based land-use planning, stricter setback zones, and community early-warning systems, while integrating climate projections into infrastructure design. However, this would require overcoming resistance from local elites and industries that benefit from current patterns of land exploitation. The balance between immediate relief politics and long-term adaptation planning will determine how far this scenario goes beyond rhetoric.
5
Civil society pressure forces belated national disaster declaration and structural reforms
Discussed by: Coalition of 113 civil society organizations, disaster management experts at Lowy Institute and University of Melbourne, international aid agencies
Sustained pressure from the 113-organization coalition, combined with continued displacement of 450,000+ people and mounting economic losses of $4.13 billion, eventually forces Prabowo to reverse course and declare a national disaster in early 2026. This unlocks additional budgetary mechanisms and international financing, but more importantly shifts political momentum toward structural land-use reform. The legal notice delivered in December becomes the basis for court challenges that compel the government to implement the 22 permit revocations as the first step of a comprehensive review of all concessions in high-risk watersheds. However, implementation remains contested as powerful industry lobbies push back and provincial governments resist central authority.
Historical Context
2021 South Kalimantan floods tied to palm oil and coal mining
January 2021
What Happened
In early 2021, Indonesia’s South Kalimantan province experienced severe flooding that displaced hundreds of thousands of people. Environmental groups and investigative outlets found that large areas of forest and peatland had been converted for oil palm plantations and coal mining, with data showing that mining and plantation concessions covered around half of the province’s land area. Analysts argued that this land-use change worsened runoff and reduced the landscape’s capacity to absorb heavy rain, making the floods more destructive than they would otherwise have been.
Outcome
Short Term
The government provided emergency relief and some officials promised tighter oversight, but no sweeping reforms to mining or plantation licensing followed immediately.
Long Term
South Kalimantan became a reference case for how extractive industries and monoculture plantations can amplify hydrometeorological disasters, informing later critiques of land-use practices in events like the 2025 Sumatra floods.
Why It's Relevant Today
The South Kalimantan floods show how the combination of legal concessions and weak enforcement can prime a landscape for catastrophe when intense rainfall occurs—a dynamic now strongly echoed in Sumatra, where mining, hydropower and plantation concessions intersect with steep terrain and high biodiversity.
2013 Uttarakhand floods and India’s hydropower reckoning
June 2013 – mid-2010s
What Happened
In June 2013, unprecedented rainfall triggered catastrophic floods and landslides in India’s Himalayan state of Uttarakhand, killing thousands and devastating the pilgrimage town of Kedarnath. Subsequent inquiries and court cases examined the role of numerous hydropower projects and road construction in destabilising slopes and altering river systems. In a landmark admission to India’s Supreme Court, the central environment ministry acknowledged that hydropower projects had aggravated the disaster, noting that maximum damage sites were located upstream or downstream of these projects and that ecological degradation and non-compliance had enhanced landslide and flood impacts.
Outcome
Short Term
The Supreme Court halted dozens of planned hydropower projects, and some existing projects faced tighter scrutiny and mitigation requirements.
Long Term
Uttarakhand’s experience helped entrench the principle that cumulative impacts and disaster risk must be factored into river-basin planning, although implementation has been uneven and development pressure remains high.
Why It's Relevant Today
The Uttarakhand case offers a precedent for how courts and regulators might treat claims that hydropower, mining and road projects worsened the Sumatra floods, especially in the Batang Toru basin where similar concerns about slope stability, deforestation and seismic risk have been raised.
2018 Kerala floods and ecological warnings on land-use
August 2018 – early 2020s
What Happened
In 2018, the Indian state of Kerala suffered devastating floods after receiving some of the heaviest rainfall in a century. Post-disaster studies found that ecological degradation—such as deforestation, harmful land use in upland areas, quarrying, and sand mining in river channels—had contributed to topsoil loss, siltation and reduced water absorption capacity. Water researchers argued that the stripping of topsoil to depths of up to two metres in some upland regions fundamentally weakened the landscape’s ability to buffer extreme rainfall, exacerbating floods and leading to drought-like conditions soon afterward as water rapidly drained away.
Outcome
Short Term
Kerala launched reconstruction efforts and commissioned studies into land-use and ecological drivers of the floods, but controversial quarrying and development continued in many areas.
Long Term
The floods intensified debate in India over how climate change interacts with land-use decisions, reinforcing calls for landscape-level planning that integrates ecology, disaster risk and development—debates that parallel Indonesia’s current discussions after the Sumatra floods.
Why It's Relevant Today
Kerala’s experience underscores that extreme rainfall events like Cyclone Senyar’s downpours in Sumatra become disasters partly because of how landscapes are managed. It strengthens the argument made by Indonesian scientists and NGOs that deforestation, quarrying, and river alteration in Sumatra have turned heavy rain into mass-casualty events.
