Man-made floods of the Yamuna call for ecosystem-led solutions

Submerged parts of Delhi served us a sharp reminder of our need to uphold the ecological integrity of damaged floodplains

- C.R. BABU

Flooding is an ecological process that is a characteristic of every monsoon river. It ensures the sustainability of a complex network of ecosystems, such as floodplain, riparian and free-flowing water ecosystems, all of which constitute a river system. Flooding flushes out sediments in various channels and sustains floodplains. Man-made flooding occurs through the upstream storing of huge quantities of water from catchment areas in dams or barrages, with subsequent releases of water once these reservoirs fill up resulting in inundation downstream. The first activity (i.e. water storage) prevents natural flooding and the second (release of huge volumes) can cause man-made flash floods, leading to not only ecological disruptions across the river system but also causing an ecological disaster for the people living in the affected downstream regions.

The flash flood witnessed in the river Yamuna from 10 to 17 July that disrupted Delhi was due to the release of 350,000 cusecs of water from the Hathnikund barrage in the Himalayan foothills after incessant rains across north India, resulting in the river’s water level rising to 208.66m, the submergence of low-lying areas on both banks and also significant back-flow in sewage-carrying storm drains, which worsened the situation.

There was a flash flood in 1978, too, when more than 700,000 cusecs of water was released from Hathnikund barrage in Haryana, but the Yamuna’s water level had risen only up to 207.49m.

So, what has been happening to Delhi’s stretch of the Yamuna—particularly downstream of the Wazirabad barrage—during the last 45 years which might have contributed to a sharper rise in the river’s level with less than half the 1978 quantity of water released this time?