Why do these things happen? Could these be prevented at all? Well, the answer lies in understanding how river systems work to create new landscape through which it flows and how we interfere with this natural process. Water flows from higher altitude points in the mountain to the lowest point in the sea. How does it get there is the story of how civilization is made and destroyed. As the river flows from the mountains to the valleys and eventually to the sea, it transports and deposits soil in the channel bottom and at bends. As the deposit at the bottom of the river piles up, the channel depth reduces and water starts overflowing the banks and creates new channels. As the deposit around the bend increases, the water starts shifting sideways to find new path. It is like when you squeeze a gel pack and you see gel finding it ways to go against the direction of your squeeze.
When a river makes a new path, the path abandoned by the river is so fertile that it attracts large immigration of farmers and associated civilization. They live there for generations oblivious of the fact that the river might come back to the path she abandoned decades or centuries ago. As her current path gets loaded with soil sedimentation under her belly and around the bends, the river gets lifted up so much so that the place around her is much lower than the river itself. It is like an overhead river! After a while, the river goes back to its first principle and flows to low again.
When she does this, millions of people who settled in the low lying land get in her way. Lives lost and property damaged and everything is under water. So what do we do to prevent this? Well, we use our engineering and technological knowledge and advancement and try to tame the Mighty Rivers. We tell the river not to flow freely. We tell her to stay her course regardless of what happens to her morphology. We build massive levee system around the banks to prevent the river from changing its course. We spent billions to create and maintain very complex levee/embankment system. As the river gets choked and can’t find a place to deposit the silt and soil it brings from upstream, the river level rises. When the river level rises, we increase the levee height by few meters. This catch-up game goes on for decades or even centuries before the river swells really big and devastate everything in her way to flow freely again. When that happens, we get Katrina and Koshi disasters and millions are left to suffer the fury of the Mother Nature.
So what is wrong with restraining a river that meander all the time? Can’t she make up her mind? Isn’t taming of natural forces that made humans what we are? Isn’t that fighting trait made civilization possible? Yes it is. But he is the difference. Good judgment is to know when to stop fighting. Good judgment is to know which fight to pick.
British knew when to stop fighting when they demolished the embankments around Damodar river (Sorrow of Bengal) in 1850s. Learning from Damodar experience, they refrained from building embankments for Koshi River (Sorrow of Bihar). But since independent, armed with the vision of engineering and technology serving to help eradicate poverty and human sufferings, the governments started building complex levee systems. This mirrored US’s initiative to build series of complex levee and pumping system in New Orleans since it bought Louisiana from the French. The government and people in both countries (India and US), doesn’t quite realize the futility of this fight. New Orleans is sinking every day and according to some predictions, it will become a sunken Atlantis by 2100.
According to the latest reports, government of India is working to repair the breached embankment and redirect the river into the confinement again. Koshi River is now flowing approximately 60 km (38 mile) east of its last path. Looking at the picture below and realizing the magnitude of the shift, it will be extremely difficult, if not impossible, to bring the river back again. Not to mention about the amount of money that will need to be pumped in to reconstruct the breached embankments.
Even if we assume that the government of India and its engineers will be able to redirect the river into confinement again, is this is a sustainable solution? Should we mess with Mother Nature once again only to be punished harshly yet gain in next 50 years! According to Hindu Legends, King Bhagiratha had to spend 1000 years praying in the wilderness to bring river Ganges from heaven to flow on earth. These girls are not easy to tame. Even when they are tamed, they are tamed to flow from heavens to earth not the other way around. That’s the lesson 101 for all the governments and their brilliant engineers. Water flows from high to low and the prudence is in letting her flow that way!
Satellite View of Koshi River in Bihar before the river changed course by approximately 60 km east during the August, 2008 flooding. See the barrage (looks like a bottleneck near the India-Nepal border) that diverts water from the river into two separate canals one to Nepal and other to India. The embankment leading upto the barrage is breached by almost a mile long and created a new flowpath cutting through the valley to join river Ganges at the bottom.
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