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  • By Laurens M Bouwer and Sebastiaan N Jonkman, Environmental Research Letters

A study published in Environmental Research Letters shows that there has been a global decrease in fatalities from storm surge events. Improved forecasting methods, better early warning systems, effective evacuation schemes, as well as coastal protection, risk-zoning and land-use planning have contributed to the declining number of fatalities and declining mortality.

Abstract: Changes in society’s vulnerability to natural hazards are important to understand, as they determine current and future risks, and the need to improve protection. Very large impacts including high numbers of fatalities occur due to single storm surge flood events. Here, we report on impacts of global coastal storm surge events since the year 1900, based on a compilation of events and data on loss of life. We find that over the past, more than eight thousand people are killed and 1.5 million people are affected annually by storm surges. The occurrence of very substantial loss of life (>10 000 persons) from single events has however decreased over time. Moreover, there is a consistent decrease in event mortality, measured by the fraction of exposed people that are killed, for all global regions, except South East Asia. Average mortality for storm surges is slightly higher than for river floods, but lower than for flash floods. We also find that for the same coastal surge water level, mortality has decreased over time. This indicates that risk reduction efforts have been successful, but need to be continued with projected climate change, increased rates of sea-level rise and urbanisation in coastal zones. […]

Conclusions: These findings have important implications. They show that the fatality risk from storm surge hazards is considerable, with high numbers of casualties per event and per year. As a hydrological hazard it is only exceeded in terms of mortality by flash floods, but storm surges affect more people. Also, benefits of efforts put in forecasting, early warning, evacuation, as well as coastal protection, risk-zoning and land-use planning, and shelters are reflected in the declining number of fatalities and declining mortality. It remains to be evaluated whether measures that have been successful so far are also effective for projected increased rates of sea-level rise. Sea-level rise could contribute to more frequent events, higher flood depths and thus less effective protection. Other factors such as subsidence and population growth can affect potential loss of life (Maaskant et al 2009). This could imply that the current decrease fatalities and event mortality could slow down or even reverse. Therefore, continued investments in the reduction of the vulnerability of coastal regions will remain important, through forecasting, emergency and land use planning as well as physical protection, especially under changing environmental and socio-economic conditions.

We found that fatalities for storm surge events are not systematically collected, and from EM-DAT events had to be selected from two events types: storm surge/coastal flood and storm/cyclone. In general, there is a reporting bias towards more recent events, which is also a well-known reality for other natural hazard event types. Better systematic collection, classification and reporting of loss of life due to coastal storm surges is recommended, to supplement current practices for other hazard types. This will enable continued monitoring and reporting on storm surge impacts, and support decisions on risk reduction efforts around the world.

Full paper