o the number of people living in flood-prone areas is growing faster than in other places, and at a much faster rate than researchers predicted, according to a study published on Aug. 4 in the journal Research. It is a worrying sign that human settlements are not prepared for increased flood risks in the climate crisis.
Researchers at Cloud to Street, a flood tracking platform, used satellite images to estimate the scale of 913 large flood events across 119 countries, and the number of people exposed to them. The study discovered that between 2000 and 2015 the total population living in areas exposed to flooding grew by between 58 and 86 million. That is a growth rate ten times higher than estimated by previous studies, which relied on modeling rather than satellite imagery to assess the number of people exposed to flooding.
The population of flood-prone areas grew 1,195% between 2000 and 2015, per the report, while the global total population increased by only 18,6% over the same period.
This summer has brought new attention to the flooding risk in developed countries. Within a matter of days in July, entire streets were swept away in Germany and Belgium, where the heaviest rains to hit northwestern Europe in generations killed more than 200 people and a 'once in 1,000 year’ flood killed more than 300 people in eastern China. Widely circulated images of the devastation, and of lesser disruption to subways in New York and London, have renewed calls in many countries for improved flood warning systems and better infrastructure to keep people safe during heavy rains.
But generally speaking, it's developing regions where people are most vulnerable to flooding and where the population at risk is increasing fast. Researchers found the fastest growing number of people at risk from floods in south and southeast Asia. Top of the list was the River Indus in Pakistan where up to 19.9 millions people were living in flood-prone areas in 2015, a 36% jump from 2000. In the basin of the Ganges-Brahmaputra River between India and Bangladesh, 134.9 million people were affected by floods in 2015, a 26% increase. And in the Mekong basin, covering parts of Vietnam, China and Laos, up to 32.8 million people are exposed, an 11% increase from 2000. The researchers identified sharp increases in the proportion of their populations exposed to floods in Western Africa, Southern Africa and Central America.
The population booms in these areas of Flood Risk are often caused by the failures in urban planning and housing provision, says Beth Tellman, Chief Scientist and Co-founder of Cloud to Street, who led the study. In many developing countries, the scarcity of formal housing programs and other financial supports forces people to settle informally on land that is hazardous and hence not being used by public housing markets. It's a problem in countries that are rapidly urbanizing, Tellman says. 'It is not as though people necessarily have a choice about wanting to live in risky areas, but it may be the only type that they're able to afford.
Many of the world's more developed regions managed to move people out of flood-prone areas between 2000 and 2015, by using tools like zoning laws and buyouts for people with homes in risky areas. Western and northern Europe, East Asia and North America are all well situated to reduce the proportion of their populations that are exposed to flooding, according to the study.
Climate change is expected to increase the number of floods worldwide. For one thing, warmer air can hold more moisture — 7% more for every 1C temperature increase. For another, melting ice caps causes sea level rise and increasing pressure on water management systems like dams. Cloud to Street projects that by 2030 the proportion of the population exposed to floods will increase across many of the world's regions, including Europe, North America, central Africa, South America and most of Asia.
According to the World Resources Institute, by 2030 as many as 758 million people would live in a 100-year flood zone. There is a 1% chance of floods each year — an increase of 179.2 million people from 2010 - 2016.
According to the WRI, only one third of this projected increase is expected to be driven by climate change. The other two thirds of the two would come from demographic shifts: more people being born in exposed areas or moving into exposed areas.
That means that, as with the past changes in flood exposure measured by Cloud to Street, our future capacity to protect people from flooding will be determined by policymaking and the use of resources. Stimultan Grants for climate adaptation - making our infrastructure and economies more resilient to floods and other changes in the weather — and wider development programs will help reduce the number of people who lose their homes, livelihoods and lives in floods, Tellman says. 'Flood exposure is not just a human problem, it's a climate problem that we've invented. And the hopeful part is that it really is within our agency to change that reality.