Flash Flood




Climate change has increased the frequency and intensity of floods. Floods are sudden onset events where normally dry land is inundated with an overflow of accumulated water that it is unable to absorb. There are several types of floods such as flash floods caused by heavy rain, river floods which are seasonal, and coastal floods associated with cyclones and tsunamis.


What can cause flooding? The frequency and intensity of floods depend on several factors: degradation of soils and the ecosystem due to unsustainable development makes it increasingly difficult for lands to absorb waters from heavy rains.

How is climate change connected to flooding? Climate change warms up the atmosphere and the air can hold 7% more water vapour for every one-degree Celsius rise in temperature. When this air rapidly cools, water vapour turns into droplets which join together to form heavy rainfall.

What can flood cause? Impacts of flash floods might be death or serious injury, immediate property damage, long-term property damage, loss of critical infrastructure, deposited sediment & silt, economic and biodiversity losses.

What cities and citizens could do? Cities can, inter alia, map the location of past floods; map areas that are susceptible to flooding based on their geography; prepare comprehensive flood risk assessment which combines data on flood-prone areas with information on vulnerable people to identify the most at-risk areas; develop flood emergency protocols and early warning systems, etc.

Rapid urbanization often entails informal settlements in areas with high flood risk, such as floodplains and riverbanks, exposing the urban poor to higher risk of floods. Nature-based solutions (NBS) can help increase onsite stormwater absorption. They can be applied from building level to landscape scale. Using multiple NBA solutions in combination with grey infrastructure components will provide the most comprehensive and effective urban development plan.

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