Climate Change Impact on Flood and Extreme Precipitation

Climate change results in more intense rainfall, which increases the chances of flooding. This is because warming means the air can hold more moisture (for every 1℃ of warming, the atmosphere can hold 7% more moisture). The hydrological cycle is expected to intensify with global warming, which likely increases the intensity of extreme precipitation events and the risk of flooding. Extreme precipitation is expected to intensify with global warming over large parts of the globe as the concentration of atmospheric water vapour which supplies the water for precipitation increases in proportion to the saturation concentrations at a rate of about 6–7% per degree rise in temperature according to the thermodynamic Clausius–Clapeyron relationship.

The Connection Between Rainfall and Water Availability

Climate change impact on flood and extreme precipitation increases with water availability. Results show an intensification of extreme precipitation and flood events over all climate regions which increases as water availability increases from dry to wet regions. Similarly, there is an increase in the intensification of extreme precipitation and flood with the seasonal cycle of water availability. Climate change also makes connecting extreme weather events more likely. For example, stronger heat and dry conditions result in parched soils. Parched soils increase the risk of flash flooding when it rains. On top of how heavy and how much rainfall there is, other factors play a role. These include soil moisture, seasonal snow cover, infrastructure and land use.

Types of Flooding and Environmental Risks

There are two main types of flooding which happen as a result of rainfall – “pluvial” flooding (surface water floods), and “fluvial” flooding (river floods). There’s also coastal flooding often caused by storm surges. Coastal flooding will worsen in places under climate change due to rising sea levels and more intense storms. Flooding can happen quite suddenly and have a very real and devastating impact on people’s lives. Flooding destroys people’s homes, communities, livelihoods, and cropland and can lead to injury or death.

Data on Global Impacts and Disasters

The list of extreme weather events and disasters is growing, as are the devastating impacts on communities. Understanding of the relationships between the climate change impact on extreme events and water availability is essential in the future-proofed planning for global change. Not long ago, Pakistan bore witness to extreme floods. Extraordinary heavy monsoon rains and melting glaciers contributed strongly to this.

• Pakistan: Over 30 million people were estimated to have been affected, with more than $30 billion in damages and economic losses.
• East Africa: Nearly 40 million people are experiencing climate-induced hunger.
• Timor-Leste: Hit by Cyclone Seroja on the 4th of April 2021; eventually the water took everything, washing away houses and the land they stood on.

Climate Change Responses

Climate change responses include adaptation (risk reduction, like building flood defences) and anticipatory action (risk aversion, like evacuating people). These are critical parts of reducing devastation. Extreme precipitation amplification may increase the intensity and frequency of flooding, imposing heavy costs to aquatic and terrestrial ecosystems, human societies and the economy. As rarer precipitation events are expected to be more influenced by climate change, these responses become even more vital.