New evidence: global mortality from storm surges is decreasing

Published: 10 November 2017

Despite widespread impacts and economic losses from recent rainfall and storm surge events around the globe, including hurricanes Harvey and Irma, there is new evidence that there are much less casualties from such events nowadays.

New research by Deltares and Delft University of Technology, published in the journal Environmental Research Letters this week, shows that in expanding coastal mega-cities, the share of deaths in the exposed population has substantially declined.

Risks have been reduced

Changes in society’s vulnerability to natural hazards are important to understand, as they determine current and future risks. With ongoing climate change, leading to more extreme rainfall and sea-level rise that aggravate coastal flooding, the need to improve protection is growing. Very high numbers of fatalities have occurred in past storm surge flood events, such as in Hurricane Katrina in 2005 with hundreds of fatalities because of flooding, and in Bangladesh in 1970 with some 300,000 deaths. This analysis of severe coastal flood events shows that on average more than eight thousand people are killed, and 1.5 million people are affected each year. However, the occurrence of very substantial loss of life (more than 10,000 persons) from single events has decreased over time, and has been very rare during the last 25 years. This is good news, as this is clear evidence that despite growing flood hazards and a multi-fold increase in population on the world’s coastline, risks have been reduced.

Monitoring and forecasting established practice

More importantly, the share of deaths (mortality fraction) is consistently decreasing almost everywhere around the world. Also for the same coastal surge water level, mortality has decreased over time. The underlying reason is that monitoring and forecasting of cyclones has now become an established practice in most ocean basins, and authorities have implemented early warning and evacuation systems. Also structural and engineered coastal protection has led to decreasing vulnerabilities and protection of many lives.

Dr. Bas Jonkman, an engineering professor at the Delft University of Technology, and one of the authors of the study said: “This implies that current risk models that take account of past events need to be updated, in order to make reliable predictions of current and future risk of loss of life. This database and information will be indispensable for many researchers and model developers”.

Dr. Laurens Bouwer, senior researcher at Deltares in The Netherlands, and lead author of the study, added: “This is clear evidence that risk reduction efforts around the world have been successful, and are paying off. Now, adaptation efforts on improving and expanding forecasting and building coastal protection must keep up with aggravating threats from sea-level rise approaching”.