Assam floods worsened by human factors, not climate change: global study

A global collaborative study has found that human factors, rather than climate change, significantly worsened the deadly floods in eastern Assam that claimed at least 103 lives between late June and early August. The World Weather Attribution (WWA), an international scientific collaboration, said heavy monsoonal rainfall in the region remained within historical norms, but land-use changes increased the impact on people and livelihoods.

The floods primarily affected Sivasagar, Charaideo and Jorhat districts in eastern Assam, along with hill catchments in Nagaland and Arunachal Pradesh. Intense downpours breached critical infrastructure, washed away agricultural land, and forced hundreds of thousands of people into relief camps. Thousands of livestock and other domesticated animals were also affected.

Scientists from India, Sweden, the Netherlands, the United Kingdom and the United States analysed historical weather records and climate models. They found that the rainfall totals were not exceptional and are expected at least every two years. However, limited data for the region means there is some uncertainty in the findings.

The WWA study, released on August 14, 2026, said the scale of the disaster stems largely from other human factors, including colonial-era land regulations, displacement, land degradation and a lack of sufficient flood mitigation. Unplanned urbanisation, rapid deforestation, wetland destruction and riverbank erosion degraded Assam's natural drainage capacity, increasing flood height and downstream impacts.

The scientists also highlighted the role of concrete engineering and hard embankments. These structures trap silt, artificially raise riverbeds and block natural runoff. "Embankments frequently exacerbate flooding and increase the risk of catastrophic breaches," they observed. The study suggested combining infrastructure with social and nature-based approaches could be more effective in mitigating floods.

The study also flagged historical vulnerability. "Historical land reallocation contributed to some indigenous communities living on marginal, flood-prone riverbanks and sandbars (chars). These historical patterns continue to trap low-income agricultural populations in cycles of repeated displacement," it said.

Adaptation efforts must broaden to include floodplain restoration, wetland conservation and expanded anticipatory disaster risk management using localised early warnings, the study recommended. It also stressed the need to understand how climate change may affect rainfall in the future, even if no clear trend is seen today.

Mariam Zachariah, a research associate at Imperial College London's Centre for Environmental Policy, said low station coverage and climate models struggling to capture processes in hilly regions create high uncertainties. "Overall findings suggest no discernible role of climate change. However, a lack of a clear trend today does not make the region immune to future warming," she said.

Emmanuel Raju, director of the Copenhagen Centre for Disaster Research, said: "Hundreds of thousands of people have been affected, with low-income agricultural families and displaced communities paying the highest price. Marginalised populations living on flood-prone sandbars and reliance on rigid concrete embankments can be a recipe for disaster."

The researchers emphasised that proactive land and river management is urgent as global temperatures continue to climb and monsoon dynamics across South Asia shift.