Intensive Versus Extensive Events? Insights from Cumulative Flood-Induced Mortality Over the Globe, 1976–2016

More attention has been paid to the cost of intensive but sporadic floods than the cost of extensive but frequent events. To examine the impacts of intensive versus extensive events, we investigated the loss structure of global flood-induced mortality by using the cumulative loss ratio, marginal benefit chart, and cumulative loss plot.Drawing on the flood-induced mortality data for four decades(1976–2016) from the international disaster database EM-DAT, we defined the levels of flood loss according to the frequency of flood-induced deaths, and calculated the cumulative mortality and the marginal benefits of flood loss prevention practices at different levels.Our analysis showed that for the world’s leading 30 countries with large flood-induced mortality and different levels of development:(1) 70% of them have the cumulative deaths from extensive floods exceeding half of those caused by intensive floods in the study’s four data decades;and (2) 80% of them tend to gain less marginal benefit with increasing levels of flood prevention, with their marginal benefits peaking at loss prevention levels of 2-year or 5-year flood-induced mortality. These results indicate that,in the long run, the cumulative deaths of extensive floods are comparable to that of intensive events, and prevention of loss from extensive events can be an efficient way to reduce the total loss. For flood risk management under conditions of climate change, extensive loss events deserve more consideration.