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Article | WTW Research Network Newsletter

A view of catastrophic flooding from across the world

By Neil Gunn and Cameron Rye | July 20, 2023

Flooding affected millions of people in the first six months of the year, with significant humanitarian and economic consequences across the world.
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There were nearly 100 major flood events recorded across all populated continents in the first six months of the year[1]. The floods that had the largest socio- economic impacts are highlighted in Figure 1, many of which were the result of heavy rainfall overwhelming rivers and urban drainage systems, or the combination of inland and coastal flooding from tropical cyclones.

Image showing flood events with largest economic impacts by dates and number of fatalities.
Figure 1. Flood events with the largest socio-economic impacts that occurred between January and June 2023.

Flooding is one of the most prevalent natural hazards, affecting livelihoods and development opportunities globally[2] [3].

Recent research from the World Bank has found that 1.8 billion people (23% of the world’s population) live in areas that are directly exposed to 1-in-100 year flooding[4]

Most of these people (89%) are in low and middle income nations.

1.8B People (23% of the world’s population) live in areas that are directly exposed to 1-in-100 year flooding

89% Are in low and middle income nations

This pattern contrasts with economic exposures, which are concentrated in higher income countries, with $9.8 trillion of economic activity (12% of the gross global product in 2020) located in be flood-prone areas.

This year has been no exception, with multiple events resulting in significant humanitarian impacts for low and middle income populations.

Heavy rains struck the Horn of Africa in March, affecting 460,000 people in Ethiopia and Somalia. This was followed by the African Great Lakes Floods in April and May, which killed over 600 people and caused extensive damage in the Democratic Republic of the Congo, Rwanda, and Uganda. In Asia, monsoon flooding and landslides occurred in Malaysia in March, while Extremely Severe Cyclonic Storm Mocha caused widespread coastal flooding in Myanmar and Bangladesh, displacing hundreds of thousands of people in May (Section 2.3). And in South America, Brazil saw multiple major flood events across 12 of the county’s 26 states. The most notable was the record-breaking flooding in the state of São Paulo in February after 680mm of rain fell within a 24-hour period.

460k People affected in Ethiopia and Somalia from heavy rains striking Horn of Africa in March 2023

600 People killed in the African Great Lakes Floods in April & May 2023, causing extensive damage in the Democratic Republic of the Congo, Rwanda, and Uganda

12/26 States of Brazil saw multiple major flood events, most notable was record-breaking flooding in São Paulo in February 2023 after 680mm of rain in 24 hours

From an economic perspective, the largest events were in New Zealand (Section 2.4), Italy (Section 2.8), and California. The Southern Hemisphere summer of 2022/2023 was the wettest on record for New Zealand’s North Island, which culminated in February with Cyclone Gabrielle producing an estimated $8.4 billion in economic damages. Intense rainfall in Northern Italy in May led to flooding that produced damages of roughly $5.4 billion, while at the beginning of the year, severe flooding in California brought on by a series of atmospheric rivers is estimated to have caused economic losses of up to $7 billion.

  • $8.4 billion economic damages from Cyclone Gabrielle in New Zealand in February 2023
  • $5.4 billion damages for flooding from intense rainfall in Northern Italy in May 2023
  • $7 billion economic losses from severe flooding in California brought on by a series of atmospheric rivers

Climate change is expected to increase flood risk by increasing the intensity of rainfall and raising sea levels[5]. Furthermore, as populations continue to grow, more people are living in flood prone areas, increasing the exposure of vulnerable communities.

Given that floods affect more people than most other natural disasters, it is imperative for governments, corporations, and other organizations to proactively invest in resilience measures. These steps include implementing sustainable infrastructure, improving early warning systems, and developing robust disaster response strategies.

In addition, accessible and comprehensive insurance solutions are vital to close the protection gap and ensure that communities have the necessary financial support to recover and rebuild after natural catastrophes.

Footnotes

  1. Based on data compiled from FloodList Return to article
  2. Parvin, G. A., Shimi, A. C., Shaw, R. & Biswas, C. Flood in a Changing Climate: The Impact on Livelihood and How the Rural Poor Cope in Bangladesh. Climate 4, 60 (2016). Return to article
  3. Balgah, R. A., Ngwa, K. A., Buchenrieder, G. R. & Kimengsi, J. N. Impacts of Floods on Agriculture-Dependent Livelihoods in Sub-Saharan Africa: An Assessment from Multiple Geo-Ecological Zones. Land 12, 334 (2023). Return to article
  4. Rentschler, J., Salhab, M. & Jafino, B. A. Flood exposure and poverty in 188 countries. Nature Communications 13, 3527 (2022). Return to article
  5. Pörtner, H. O. et. al. IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (Intergovernmental Panel on Climate Change, 201 Return to article
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Authors

Head of Flood & Water Management
WTW Research Network
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Head of Modelling Research and Innovation
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