Floods are destructive, right. People should stay away from them. That's what commonsense suggests. However over millennia, people have preferred to stay in areas regularly affected by flooding. An excellent example is offered by the lower reaches of the Ganga, which has traditionally been the most densely populated area of the subcontinent.
Living with floods: The people of these regions devised ways of living with the floods. A system used in Bengal perhaps best illustrates this. The river basins had a number of channels, which were not used during most of the year. The villagers also built low mud embankments along the riverbanks. When the river flooded, the villagers would deliberately breach these embankments so that the water flowed into these channels, called kaninadis or blind rivers, which received the excess flows, which helped divert and store the floodwater.
Usually the top layer of the floodwater spread in a rather thin layer over the flood plain, which largely consisted of fields. The silt, largely fine alluvium, would be of great benefit for the soil as nutrient-rich alluvium got deposited each year.
Side effects: The waters also brought in algae and fish eggs, which would then spawn in the local village wetlands. There were other benefits too, especially in disease control, as the young fish would eat the mosquito larvae, thus helping check maladies like malaria.
But perhaps the greatest benefit lay in the gradual spread of floodwater, which did not cause extensive loss of lives or property.
Taming the flow: The colonial period, in its drive to 'upgrade' technology, decided to tame the floods of Bengal. One of the very first things that was done the conversion of mud embankments to concrete ones. While perhaps the theory was correct to an extent, what proponents of the 'concrete school forgot was the sheer strength of Himalayan rivers like Kosi, Gandak or Tista.
The ploy worked in the initial stages. The waters did get contained in years when the flooding was of lesser magnitude. People were encouraged to build their houses on or near the embankments, which offered them closer access to the water. However when the velocity of water became fierce, then the river burst through even the walls of concrete, causing sudden flooding.
Not only was this flood without a warning, the pressure built up caused the force with which the floodwater spread to be many times more destructive, often killing people in hundreds and causing immense loss to property, occasionally sweeping away even entire villages or kasbas.
River basin approach: The Damodar, India's first river to have an integrated river development programme - the Damodar Valley Project, (a step now being sought to be implemented on all of India's rivers) used to be rather innocuous river till the early twentieth century. It was transformed into Bengal's sorrow as an extensive system of concrete embankments were built, and which to this day continue to cause havoc when these embankments are breached.
Despite calls from water experts and endorsements by political parties of late, there is still effort to involve the local community in the management of water, including in the control of floods. Floods in almost all rivers follow the monsoon pattern and are increasingly getting more and more destructive despite a manifold increase in technology, both in warning and other infrastructure.
The embankment situation has however not really changed after independence. Even now the embankments built are of concrete - more than 500 kilometres have been built since the 1950s.