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

Source: The post is based on the article “Man-made floods of the Yamuna call for ecosystem-led solutions” published in Live Mint on 21^st July 2023.

Syllabus: GS 3 – Disaster Management

Relevance: measures needed to control flash floods in Delhi.

News: The article explains the reasons behind the floods in Delhi and provides measures to prevent them.

How are manmade flash floods caused?

Man-made flash flooding is caused by dams holding massive volumes of water and then releasing it downstream. It has the potential to cause ecological changes and calamities in downstream locations.

The flash flood on the Yamuna River that caused havoc in Delhi was caused by the discharge of 350,000 cubic meters of water from the Hathnikund barrage.

This resulted in the river’s water level rising, the submergence of low-lying areas on both banks and significant back-flow in sewage-carrying storm drains, which worsened the situation.

Delhi also witnessed a flash flood in 1978. However, during that period, a larger volume of water was released from the dam compared to this year, but the water level of the Yamuna did not experience a significant rise.

What has caused a sharper rise in the water level of the Yamuna this year?

First, over time, the width of the Yamuna’s floodplains in certain areas has significantly decreased from the river channel, and in some sections, there are no floodplains left.

This has led to a decrease in the flood-carrying capacity of these floodplains that usually act as a flood-way for flood water. Bunds, guide bunds and other structures built along the flood plains have also reduced the area of flood plains.

Second, there has been a loss of floodplain catchment wetlands which are capable of absorbing large volumes of flood water. Their loss over the years also contributed to the enhanced level of flood water this year.

Third, there has also been an increase in the number of bridges (road, railway and metro) across the river between the Wazirabad and Okhla barrages. These pillars act as a water-resistance, thereby increasing the level of flood water.

Fourth, concretization of floodplains in the name of river ghats has reduced the flow of water. More dams/barrages on the river upstream of Palla also contributed to frequent floods downstream.

Must Read: Extreme rainfall events and urban floods: Explained

What steps can be taken to prevent Delhi from flooding in the future?

1. Building bridges over the river should be prohibited.
2. Avoiding dense plantations of trees and woody plants on floodplains, as trees provide resistance to flood water.
3. Delhi’s water supply can be improved by the restoration of catchment wetlands on floodplains that collect floodwaters. Off-river reservoirs can be built for this purpose.
4. The creation of a network of biodiversity parks throughout the floodplains, similar to the Yamuna Biodiversity Park, would not only help rejuvenate the river, but will also assist lower flow velocity and store floodwater.
5. All wetlands should be restored to retain surface run-off and should not be exploited for solid waste disposal.
6. To keep flows in check, open lands around main drains should be left free. Natural storm drains should not be used as sewers.
7. Establishing a single authority to oversee sustainability and protect the ecological integrity of the Yamuna’s Delhi stretch.