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Climate Change & Floods

  Mar 17, 2020

Climate Change & Floods

What is a flood?

A flood is the accumulation of water over normally dry land. It’s caused by the overflow of inland waters (like rivers and streams) or tidal waters, or by an unusual accumulation of water from sources such as heavy rains or dam or levee breaches.

How do you classify major types of floods?

1. River Flooding

2. Coastal Flooding

3. Flash Floods and

4. Urban floods

What causes flooding?

Many factors can go into the making of a flood. There are weather events (heavy or prolonged rains, storm surge, sudden snowmelt); and there are the human-driven elements, including how we manage our waterways (via dams, and reservoirs) and the alterations we make to land. Increased urbanization, for example, adds pavement and other impermeable surfaces, alters natural drainage systems, and often leads to more homes being built on floodplains. In cities, under-maintained infrastructure can lead to urban flooding. More and more, flooding factors are also linked to climate change.

How is climate change linked to floods?

While our warming world may not induce floods directly, it exacerbates many of the factors that do.  IPCC (Intergovernmental Panel on Climate Change) noted in its special report on extremes, it is increasingly clear that climate change “has detectably influenced” several of the water-related variables that contribute to floods, such as rainfall and snowmelt.

How Does Climate Change Lead to Flooding?

These are some of the key ways climate change increases flood risks:

Heavier Precipitation: A warmer atmosphere holds and subsequently releases more water. Basically, because of global warming, when it rains, it pours more. Such was the finding of a study by the National Oceanic and Atmospheric Administration (NOAA) of the USA. Heavier rainfall does not automatically lead to floods, but it increases the potential for them. And even moderate amounts of rainfall can cause serious damage, particularly in places where urban flooding is on the rise.In regions where seasonal snowmelt plays a significant role in annual runoff, hotter temperatures can trigger more rain-on-snow events, with warm rains inducing faster and often earlier melting.

2.  Climate change is increasing the frequency of strongest storms, a trend expected to continue through this century. Stronger storms bring greater rains.

3. As ocean temperatures rise and the world’s glaciers and ice sheets melt (phenomena exacerbated by climate change), global sea levels are rising. Our oceans are approximately seven to eight inches higher than they were in 1900 (with about three of those inches added since 1993 alone)—a rate of rise per century greater than for any other century in at least the past 2,000 years. IPCC predicts seas around the world will rise anywhere from one foot to more than four feet above 2000 levels by century’s end. Flooding will occur as sea levels rise.

4. In addition to amplifying storm surge because the water starts at a higher level, sea level rise increases high-tide flooding.

How is India impacted? Give India specific details

Climate change has had extreme impacts in India. Rise in average global temperatures have led to a worrying trend of no rain for long periods and a sudden spell of excessive rainfall, causing extreme weather events, particularly floods which took lives, destroyed homes and agricultural yields as well as resulted in huge revenue losses.  Nine states of India were affected by floods due to heavy rains in July-August 2019. Hundreds of people died and millions of people were displaced due to it. 

Temperatures in the Himalayan region are projected to rise up to 2.6 degrees Celsius and also increase in intensity by 2-12 per cent by 2030s. This will result in increased flash floods events leading to large scale landslides and loss of agriculture area affecting food security. 

Monsoon rainfall in 2018 was the sixth-lowest since 1901, according to the India Meteorological Department (IMD). It was also the sixth-warmest year since 1901, when recording started. This is presumed to be partly the result of the changing climate.