Upper Assam floods: Experts seek answers beyond rain, flag changing Dikhow basin

A CORRESPONDENT

DIBRUGARH: The devastating floods that swept through Upper Assam in July cannot be explained by heavy rainfall alone, experts said at a brainstorming session at Dibrugarh University on Friday, pointing to a combination of extreme rainfall in the upstream hills, changes in the Dikhow river basin, river morphology, sedimentation, mining, deforestation, altered drainage, and gaps in disaster preparedness.

The discussion, organised by the Centre for Atmospheric Studies, Dibrugarh University, under the theme ‘Need of an integrated understanding through trans-disciplinary approach for effective risk reduction and adaptation,’ sought to examine what turned an extreme rainfall event into a disaster of such magnitude and what could be done to reduce the risk of similar events in the future. 

The session was moderated by Prof Kalyan Bhuyan, while Dr Partha Jyoti Das, Professor of Practice at Dibrugarh University, delivered the keynote address and set the framework for the discussion. 

Prof Jogendra Nath Sarma said that the July flood needed to be examined in the context of the exceptionally heavy rainfall in Nagaland, particularly in Mokokchung, Mon, Tuensang, and Longleng, which feed into the wider river systems of Upper Assam. However, he argued that the rainfall itself was only one part of the explanation and drew attention to what he described as the changing basin architecture of the Dikhow river. 

One of the more significant possibilities raised by Sarma was whether a temporary dam-like obstruction may have developed in the upstream Dikhow region before the flood, possibly because of accumulated debris and other material.

Prof Pradip Kumar Bhuyan brought the climate dimension into the discussion, pointing to the warming observed in Northeast India over the longer term and changes in rainfall behaviour. 

Prof Tapos Kumar Goswami brought the geological and geomorphological setting of the Naga hills into the discussion, highlighting slope steepness and the Naga Thrust system as important factors in understanding erosion and hillslope instability. 

Joining the discussion online, Prof Bashabi Gupta emphasised the need for greater preparedness in the face of very high rainfall, flash floods, and widespread inundation in Nagaland and Arunachal Pradesh.

Dr Devojit Bezbaruah focused on the effects of coal mining and other land-use disturbances on the Dikhow system, particularly the overburden and debris generated during mining and exploration. He also pointed to the possible role of embankments in enhancing flood devastation under certain circumstances.

Dr Shukla Acharjee, who also participated online, emphasised the need to understand changes in the soil and riverine structure of the Dikhow and their implications for the floodplain.

The discussion repeatedly returned to the consequences of sedimentation, hillslope degradation, and declining channel-carrying capacity.

The brainstorming session concluded with a broad consensus that Upper Assam’s flood risk requires a trans-disciplinary and basin-wide approach, with scientists, government agencies, and local communities working together on both risk reduction and adaptation.

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