Floods less deadly, despite climate change and overpopulation

Only the low-income countries are lagging behind: there, the mortality rate per flood in the past twenty years was actually higher than before, according to the Delft figures. A sign that there is probably still room for improvement, thinks professor of water management and climate adaptation Jeroen Aerts (VU Amsterdam) after inspecting the Delft study. ‘This study confirms that adjustment pays off. But you have to have money for it.’

Between three and ten thousand people die every year in floods. For the analysis, professor of hydraulic engineering Bas Jonkman and colleagues examined 5,600 flood disasters from the past fifty years. The average number of people killed per disaster decreased sharply during that time, from roughly three hundred in the 1970s to an average of thirty in the early 2020s.

There are fewer deaths per disaster and the average number of people affected per flood has also halved. ‘While at that time the world population doubled, and many people started living in coastal cities and vulnerable areas such as deltas and along rivers,’ says Jonkman. ‘Countries have become better at preventing floods in whole or in part, and at warning people in time, for example, of approaching storm surges.’

It is significant that more predictable disasters such as hurricanes cause fewer deaths than sudden disasters such as flooding rivers. As an example, Jonkman mentions the flood that claimed more than 220 lives in July 2021 after extreme rain, mainly in the German Ahr valley. ‘The river suddenly overflowed its banks. People hardly saw that coming.’

But the results are not proof that the technology will solve all climate problems, Jonkman warns. ‘Our results show that technological adjustments are an important part of climate policy. But the question remains how long we can withstand it if we start to feel the consequences of warming more strongly. The standard answer is that you have to do both: adapt and reduce greenhouse gases.’

Early warning

Aerts also points out that the material damage caused by flooding is increasing. ‘That seems to be an indication that the warning systems and storm bunkers in particular have improved, but that the dikes are lagging behind.’ After the floods in Bangladesh (1991, 140 thousand deaths) and Myanmar (2008, 138 thousand deaths) and the Asian tsunami (2004, 230 thousand deaths), many countries installed alarm systems. According to an inventory by Aerts, two out of three countries now have some form of an early warning system.

The middle-income countries benefited most from this, as can be seen from the Delft graphs: there the risk of dying per flood disaster was halved. In the poorest countries, the risk of death increased by about 30 percent. The lethality of floods also fell sharply in rich countries, but the numbers are too small to be statistically certain.

The Delft study, which is available online as a pre-publication, is grist to the mill of countries and organizations that believe that rich countries should contribute more to the preparation for climate change in poor countries. For example, at the climate summit in Dubai next month, a compensation fund for climate damage in poor countries is on the agenda.

Follow-up research should show in more detail how exactly the climate influences water disasters in the developing world, Jonkman believes, and which measures are most effective.