Explained: What are flash floods and why they may increase in the next few years

Source: The post is based on the article “Explained: What are flash floods and why they may increase in the next few years” published in Indian Express on 21st August 2022.

What is the News?

Himachal Pradesh Chief Minister has expressed concern over the loss of life and property due to torrential rains and flash floods.

What are Flash Floods?

Excessive or continuous rainfall over a period of days, or during particular seasons can lead to stagnation of water and cause flooding. Flash floods refer to such a situation but occur in a much shorter span of time.

For instance, the US’s meteorological agency, the National Weather Service, says flash floods are caused when rainfall creates flooding in less than 6 hours.

It adds that flash floods can also be caused by factors apart from rainfall, like when water goes beyond the levels of a dam.

Note: In India, flash floods are often associated with cloudbursts – sudden, intense rainfall in a short period of time.

Where do Flash Floods commonly happen?

Flash flooding commonly happens more where rivers are narrow and steep, so they flow more quickly.

They can also occur in urban areas located near small rivers since hard surfaces such as roads and concrete do not allow the water to absorb into the ground.

How common are Flash Floods in India?

India is the worst flood-affected country in the world after Bangladesh and accounts for one-fifth of the global death count due to floods.

Flash floods have been commonly witnessed in cities like Chennai and Mumbai. Depression and cyclonic storms in the coastal areas of Orissa, West Bengal, Andhra Pradesh and others also cause flash floods.

What is the reason for Flash Floods in India?

According to National Disaster Management Authority data, one of the reasons for flood situations occurring so frequently is that nearly 75% of the total Indian rainfall is concentrated in a short monsoon season of four months (June to September). As a result, the rivers witness a heavy discharge during these months.

Note: According to the National Flood Commission, about 40 million hectares of land in the country are liable to floods and an average of 18.6 million hectares of land are affected annually.