Increased Risk of Global Floods Due to Climate Change

October 9, 2013

One frequently cited effect of climate change is the increased risk of flooding which could cause serious loss of life and property in many parts of the world.  Recent work by Hirabayashi et al (2013) uses the output from 11
different climate models to estimate the increased global risk of floods due to climate change.  Using a river routing model to calculate future river flows and flooding areas, they were able to predict that floods will become more frequent over 42% of the earth’s surface.  Areas including Southeast Asia, India, eastern Africa and the northern Andes are likely to be hit the hardest.  In fact, floods that used to occur every 100 years are predicted to start occurring every 5-25 years in many areas.  This is especially unfortunate given the high concentration of impoverished and vulnerable communities in those regions who will struggle to adapt to a changing climate.  The researchers also looked at the specific effects on a number of the world’s most important rivers. 

They found that the Ganges, Mekong and Nile rivers are likely to experience what were considered 100 year floods during the 20th century every 10 years during the 21st century.  The human costs of such flooding are likely to be staggering.  Even a relatively moderate 2ºC global temperature increase could lead to 27 million people being exposed to flooding events worldwide.  Larger temperature increases of 4-6ºC could lead to an estimated 62-93 million people affected.  Given the predicted geographical location of these flooding events, it is likely that some of the world’s poorest regions will bear a disproportionate share of this burden.


Hirabayashi, Yukiko, Roobavannan Mahendran, Sujan Koirala, Lisako Konoshima,
Dai Yamazaki, Satoshi Watanabe, Hyungjun Kim, and Shinjiro Kanae. (2013). ”Global flood risk under climate change.” Nature Climate Change, 3, 816–821, doi:10.1038/nclimate1911