Flood: The River Kosi

The Kosi1 is one of the most flood-prone rivers in India. The brunt of its fury is borne by the northern Indian state of Bihar and the Kosi is aptly also known as the ‘Sorrow of Bihar’. Like many other flood-prone rivers, the root cause lies in the extraordinary amount of silt that the Kosi carries from the Himalayas to the plains of Bihar. The silt deposition raises the river bed and gravity causes the river to seek out a new course – in this manner, it has been estimated2 that the river Kosi may have moved westwards by an incredible 210 km in the last 250 years. During the 1950s, in an effort to provide “permanent salvation from floods”3 the Indian government embarked on a program of building embankments on the river to curb the periodic shifting of the Kosi’s course – the embankments were aimed at converting the unpredictable behaviour of the river into something more predictable and by extension, more manageable. It was assumed that the people of Bihar would benefit from a stabilised and predictable river.

Unfortunately, the reality of the flood management program on the river Kosi has turned out to be anything but beneficial. The culmination of the failure of the program was the 2008 Bihar flood4 which was one of the most disastrous floods in the history of the state. So what went wrong? Was this just a result of an extraordinary natural event? Most certainly not – As Dinesh Mishra notes5, the Kosi carried only 1/7th of the capacity of the embankments in 2008 and at various points of time since the 50s, the river had carried far greater quantities of water without causing anywhere near the damage it caused in 2008. The system was thus unable to withstand even modest adverse shocks after prolonged stabilisation.

So what caused this loss of system resilience? As Dinesh Mishra explains6:

By building embankments on either side of a river and trying to confine it to its channel, its heavy silt and sand load is made to settle within the embanked area itself, raising the river bed and the flood water level. The embankments too are therefore raised progressively until a limit is reached when it is no longer possible to do so. The population of the surrounding areas is then at the mercy of an unstable river with a dangerous flood water level, which could any day flow over or make a disastrous breach.

As expected, the eventual breach was catastrophic – the course of the Kosi moved more than 120 kilometres eastwards in a matter of weeks. In the absence of the embankments, such a dramatic shift would have taken decades. With the passage of time, a progressively greater degree of resources were required to maintain system stability and the eventual failure was a catastrophic one rather than a moderate one. The stabilisation did not merely substitute a series of regular moderately damaging outcomes for an occasional catastrophic outcome (although this alone would be a cause for concern if a catastrophic outcome was capable of triggering systemic collapse). The stabilisation transformed the system into a state where eventually even minor and frequently observed disturbances would trigger a catastrophic outcome.

When faced with the possibility of a catastrophic outcome, the managing agency has two choices, neither of which are attractive. Either it can continue to stabilise the system using ever-increasing resources in an effort to avoid the catastrophic outcome. But this option must only be followed if the managing agency has infinite resources or if there is some absolute limit to this vicious cycle of cost escalation that is within the resource capabilities of the agency. Or it can allow the catastrophic outcome to occur in an effort to restore the system to its unstabilised state. But this option risks systemic collapse – it is not just the unprecedented nature of the outcome that we have to fear, but the fact that the adaptive agents of the complex system may have lost the ability to deal with even the occasional moderate failures that the unstabilised system would throw up.

For example, in the pre-embankment era when the Kosi was allowed to meander and change course in a natural manner, the villagers on its banks had a deep
understanding7 of the river’s patterns and its vagaries. The floods sustained the fertility of the soil and ensured that groundwater resources were plentiful. This is not to deny that the Kosi caused damage but because the people had adapted to its regular flooding patterns, systemic damage only occured during the proverbial 100-year flood. This highlights an important lesson in complex adaptive systems: The impact of disturbances cannot be analysed in isolation to the adaptive capacities of the agents in the system. If disturbances are regular and predictable, agents will likely be adapted to them and conversely, prolonged periods of stability will render agents vulnerable to even the smallest disturbance.