This year, the monsoon in Nepal was extended by nearly a month and ran into late September. It finally bid farewell with an extended four-day spell of rainfall (jhari) over the Kosi river catchment in east Nepal. As the curtain closed on the rainy season, it was time once again to breathe a sigh of relief that the Kosi embankment had not broken. The lives and livelihoods of millions in a strip of the Nepali plains and downstream Bihar and had been spared.

Given the governmental inertia in Patna, Delhi and Kathmandu, a calamity on the Kosi flats seems inevitable. When it strikes, it will not be a natural disaster but a largescale human-made catastrophe. The tragedy will be the result of what is euphemistically called “river engineering” and what an angry activist calls “hydraulic despotism” – a colonial-era holdover that continues to guide South Asia’s water bureaucracy. The structures it has built on the Kosi and continues to maintain poorly are by far the worst examples of technological arrogance in this part of the world.

The groundwork for the inevitable tragedy was laid nearly 70 years ago, when the great North Bihar flood of August 1953 spurred the leaders of newly independent India to imprison the Kosi’s flow. Jawaharlal Nehru ordered the river to be jacketed between more than 100 km of embankments running down from Nepal and through Bihar.

When they realised that the levees – walls built on the side of rivers to prevent flooding – would deprive the farmland of water, the planners retroactively decided to build the Kosi Barrage, just inside Nepal at Bhardaha, to divert water to the eastern and western canals.

An imposing structure

While the barrage is only part of the problem, there is excessive focus on it because of the imposing structure: it is more than a kilometre long, with 56 sluice gates and a highway running on it. The main problem, though, is the levees that run more than 120 km down the two banks above and below the barrage in Nepal and Bihar. The result of the embankment mania that continues its grip over South Asia, the Kosi levees were just the wrong structures to build.

Things have remained at standstill for decades now, even though sanity and accountability require getting over the political inertia and working on people-oriented, science-backed alternatives to the Kosi embankments. The lowest-common-denominator approach in terms of alternatives to the levees has been to propose a high dam and reservoir upstream in Nepal. But that, as we will see, is not the solution.

A 360-degree videography above the Kosi Tappu, showing Kosi Barrage, in mid-September 2020. Drone videography by Ajaya Upadhyay.

Even though the Kosi is the source of the life-giving silt deposited over millennia that makes the region so fertile and densely populated, the river is called the “Sorrow of Bihar”. Actually, it is the embankments that need to be given that title, for having deprived the land of silt and having contributed to water-logging, displacement and disease.

Since 1959, when the embankments were completed, the silt and sediment have had to settle within the straitjacket instead of being spread across the Kosi’s “inland delta” of eastern Bihar. This has meant that more than five centimetres is added to the level of the riverbed every year. As a consequence, we now have a situation where the largest tributary of the Ganga flows on a raised platform above the outlying floodplain. Essentially, the Kosi flows on a plateau that is between four metres to five meters higher than the area outside. It is a river in disequilibrium.

Standing on the embankment, you can easily see the stark elevation differential, inside and outside. It takes just a little imagination to consider what will happen when the river breaches the levee and is unleashed in full force into the floodplain during peak flood. When the embankment breaches while the Kosi is in spate any one of these upcoming monsoons, the scale of devastation in lives lost is bound to be beyond tens of thousands.

As the silt accumulates annually, relentlessly, it is clear that something must be done. But the politics of populism and unaccountability is so intense, there is little appetite for the Indian authorities to plan for the people. The easiest way out has been “topping up” the embankments and deluding the public that there is a plan – in the form of the Saptakosi High Dam.

The Saptakosi

The Kosi, or Saptakosi, is the largest tributary of the Ganga. Its mountain watershed encompasses most of eastern Nepal, from Kathmandu Valley all the way to Sikkim, reaching deep into Tibet. The river’s total catchment area is 84,740 sq km, of which 22% is in Tibet, 40% in Nepal and 38% in the Bihar plains. The three stems – the Tamor, Arun and Sunko – meet in the tri-junction of Tribeni before flowing swiftly down a deep gorge, past the holy site of Barahachhetra, before emptying into the plains beyond the village of Chatara.

Tamor, eastern branch of the Kosi, comes down from the flanks of the Kanchhenjunga massif. The central stem, Arun, goes straight north to drain a good part of the Tibetan plateau northeast of Mount Everest. Sunkosi, coming in from the east, gathers up five tributaries all the way to the Kathmandu Valley rim.

All in all, seven tributaries make up the Saptakosi.

The Himalaya is a young and fragile geological formation that is rising a couple of centimetres every year due to plate tectonics, and the Kosi cuts away at the bedrock, delivering a massive load of soil and sand into the plains. The river brings down 120 million cubic metres of sediment every year, one of the heaviest sediment-carrying rivers on Earth. Since 1957, the Kosi has deposited 450 million cubic metres of sediment above the Kosi Barrage in Nepal, and more than a billion cubic metres downstream in Bihar between the embankments.

It is the silt of the Kosi and other tributaries that created the Ganga maidaan, the fertile mud making it attractive for dense habitation. As the Kosi emerges from the gorge, it deposits pebbles and coarser sand in the upper reaches, while the finer silt including organic material replenishes the fields of northeast Bihar.

The Kosi river basin. Credit: On the water hazards in the trans-boundary Kosi River basin, Natural Hazards and Earth System Sciences.

The communities of the floodplain have always valued the annual inundation, adjusting to the high waters for a few weeks each monsoon. The situation would become difficult with extended high floods, such as when the Brahmaputra and Ganga peaked simultaneously, as also the Mahanadi and Teesta. On the whole, however, the floods would disappear as quickly as they arrived, leaving the soil invigorated. The people lived in a give-and-take with the Kosi.

These past decades, the embankments have not only kept the water and sediment locked in, but delivered the finest silt into the flow of the Ganga rather than the fields of Bihar. The other, tragic and unintended consequence of the levees has been to actually increase of inundation due to drainage obstruction. And no one spares a thought for the one million citizens of India who remain within the embankments, deemed acceptable collateral damage in the great technological leap forward.

Even as 3,500 km of levees have been built in Bihar for flood protection, the flood-prone area has quadrupled to 6.8 million hectares. Even though the original plan was to protect 214,000 ha from annual floods, approximately 426,000 ha has been lost to waterlogging due to the Kosi embankments alone. Says the South Asia Network on Dams, Rivers and People, “The real crisis of Northeast Bihar is not floods but drainage.”

In a 2006 paper titled Kosi: A Review of Flood Genesis and Attempts to Solve this Problem, officials of India’s Central Water Commission AK Jha and DP Mathuria stated: “The engineering approach has proved to be far too insufficient in its objectives … and soon the embankments would be ineffective to control the Kosi floods. It would thus be naïve to embark upon finding of this menace through structural measures.”

The attempt at “taming the Kosi” was nothing more than playing dangerously with nature and adding to human misery.

Mad ideas

Ironically, the victimisation of the floodplain population was done not by the colonial administration but the representative system of governance right after Independence. Distanced politicians and engineers decided what was good for the masses, ignoring matters of culture, geology, history and river morphology. In one stroke, they took away the Kosi’s ability to replenish the soil and created a ticking time bomb of sedimentation.

Seeking to answer the Bihar floods with something attractive and overwhelming, the new rulers of India zeroed in on the need for a high dam to hold back the Kosi waters, built above Barahachhetra in the Nepali mountains in order to create a storage reservoir. The engineers proposed embankments to tie down the Kosi as something that was immediately possible. Nehru decided to go for it.


Since the late 1950s, a good part of the political economy of Bihar has been defined and controlled by the business of contracting out money to strengthen and protect embankments. Derisively called the “embankment mafia”, a network of technocrats, politicians and contractors conspires to ensure that alternative measures are not discussed seriously, unless it is the proposed high dam, while the annual charade of embankment fortification continues.

Those in power are willing to live with the clear and present danger of the Kosi embankments, to bleed the exchequer as a steady source of annual loot. About (Indian) Rs 3 billion is spent annually for constructing and repairing embankments in Bihar. A good part of this goes to repair work on the Kosi. Up to 60% of the money charged to strengthen embankments is said to go into lining the pockets up and down the Bihari politico-bureaucratic hierarchy.

The tilt of South Asian hydro-engineers towards technological fixes is well known. Their Western gurus were the builders of dams, levees and barrages in Europe and North America. But the siltation in the Himalayan rivers is of a different magnitude, which the engineering tomes do not address. Besides, the policymakers were bedazzled with the idea of “taming wrathful rivers” and neglectful of the historians and social scientists who would have told them of the ability of communities to absorb high-water periods. In addition, they failed to consider the social injustice that is caused when technological fixes go wrong, leading to creation of “oustees”, large-scale marginalisation and impoverishment.

The latest policy departure is to tie the proposed Saptakosi High Dam to the grandiose river-linking project so beloved of Bharatiya Janata Party leaders. This is a wildly expensive scheme meant to transfer water from surplus areas of the subcontinent to water-deficient areas.

In their published plans, the India’s river-linking technocrats take Nepal’s territory for granted – as if it is there for the taking – and do not contemplate the inevitable rejection by the lower riparian regions of the Ganga and Brahmaputra. As with the building of the Kosi embankments and barrage, the river-linking scheme is a mad idea of incompetent technocrats ingratiating themselves to clueless politicians with inflated egos.

Aftermath of the breach

Over geological and historical time, through a process known as avulsion, the Kosi has always filled its existing channel with sediment, overtopped and changed course. Over two centuries till it got jacketed in the late 1950s, this dynamic river shifted channels and moved 120 km westwards over the inland delta (or fan), away from Purnia and towards Saharsa. If unrestrained, given the slope of the land, the river would have progressively shifted back eastward on its paleo-channels.

Human intervention locked-in the Kosi, but the river kept bringing soil, sand and pebbles, adding to the level of the riverbed. This is how the largest tributary of the Ganga – and the largest flow to leave the Himalaya mountains between the Brahmaputra and the Indus – ended up where it is now, on its “super-elevated’’ bed. A break in the embankment on either side due to poor maintenance, a cloudburst flood, a glacial lake outburst flood or even sabotage, could spell disaster.

Over two centuries, the Kosi moved 120 km westward over the fan of the inland delta.

When the breach occurs, one dare not even predict the number of human lives that would be lost, the livestock drowned and farmlands disappeared. A demographic, economic and political crises would follow – pauperisation, out-migration, child trafficking and exploitation of every kind. Against this scenario, the commanding polity in Patna and New Delhi seems paralysed: it is so much easier to hand out the embankment largesse and get through another year, then another.

Each time there is a flood, during the little window of coverage that the Indian media allows the backwaters of Bihar, the Centre and state governments have always pointed the finger accusingly at Nepal for “releasing” the waters. No matter that they know full well there are no reservoirs in Nepal to impound flood waters for release. The two barrages (on the Gandak and Kosi, not meant to hold water) are close to the border and manned by the Indian authorities.

If the public’s anger rises beyond a certain measure during the monsoon, India’s authorities have another answer ready – the flooding will end as soon as Nepal allows the Saptakosi High Dam to be built. For decades, the water bureaucracy of India that is concentrated in Patna has done little else but repeat this mantra of the high dam, with little concern for river morphology, let alone sociological, geopolitical and security matters.

When the devastating breach does happen, amidst the ensuing tragedy and public anger, the Saptakosi High Dam will suddenly become the one-point agenda backed by the might of the Indian state. We will arrive at such a point of popular appeasement that it will be impossible for the floodplain activists of Bihar or the Nepal’s polity to push back.

Message from Kosi Mata

The Kosi embankments have seen dangerous breaches eight times since they were constructed, but evidently the life and livelihood of the people of the dehat are not adequately valued, and Bihar authorities got away without being held accountable. Seemingly in exasperation, Kosi Mata sent a strong message with the east embankment breach of August 18, 2008, 12 km north of the barrage. Even as the residents of nearby Kusaha village watched aghast, standing further up the east embankment, the river cut through the earthwork and gushed down like a cataract.

“At first there was a kind of fog coming up from the rushing waters,” one witness recalled. Within minutes, the roiling waters had gouged out a kilometer of the eastern embankment and before you knew it nearly all of the Kosi’s flow was diverted through this cut, hurtling southeast into the ‘flood-protected’ area of Bihar. There was no question of the river finding its way back to its ‘designated channel’ because the embankment came in the way, and in any case the water would have to ride up a ledge to gain the Kosi riverbed.

“It was like a sea had suddenly appeared, extending as far as the eye could see to the south and east, beyond Nepal into India,” the witness said. The breach at Kusaha killed 70 people in Nepal and more than 250 in India. Five districts of Bihar were submerged, displacing nearly 3 million people in Supaul, Araria, Purnia, Madhepura and Saharsa. Altogether, 340,000 hectares of standing crop was destroyed, and uncounted livestock swept away. Having caught one of its old discarded channels, the Kosi deposited million tons of sand on fields and villages.


The Kusaha breakout occurred when the Kosi discharge was only at 2,830 cubic meters per second (cumec), which is only a tenth of the 28,300 cumec for which the embankments were designed. Further, the Kosi was not even in spate at the time, its flow at 60% of what is normal for that time in August. The question in everyone’s mind should be: what will happen to the millions in Northeast Bihar if there is a sudden breach during high flood?

It has already been a dozen years since the Kosi sent her warning, and in the intervening time the planners have done nothing other than pile sandbags on the levees. Meanwhile, the height of the riverbed would have risen by more than half a metre during this period, adding further to the disequilibrium of the Kosi.

Kanak Mani Dixit is a writer and journalist, and founding editor of the magazine Himal Southasian.

This is the first of a three-part series on the Kosi river disequilibrium. Read the series here.