Potential for Various Riverine Flood DRR Measures at the Global Scale

Abstract

Flooding events that occur on the Earth’s rivers annually cause large amounts of monetary and human impacts. These impacts are expected to increase through the end of the 21st century for various reasons. Decision makers must take action now and implement disaster risk reduction measures to avoid large increases to damages in the future. On the global scale, we model three disaster risk reduction measures – namely dykes and levees, dry-proofing, and zoning restrictions – and evaluate them in terms of their economic performance (via benefit-cost analysis) as well as their ability to achieve a predefined risk reduction target based on current relative levels of risk, referred here to as efficacy. We show that large decreases to future expected annual damages can be obtained if certain measures are implemented throughout various sub-national regions of the world, most notably in regions with high levels of projected population growth. We see that the two aforementioned evaluation metrics, when used to select a disaster risk reduction measure for implementation, result in different outcomes for three-fourths of the world’s sub-national regions, most often in East Asia and the Pacific as well as South Asia. In these instances, decision makers must choose what is more important – achieving a risk reduction target, or having investments pay-off in the long run, even if it requires a large amount of up-front capital. This opens the dialogue for incorporating other non-monetary values into the decision making process for disaster risk management, and also points to the potential of hybridising riverine adaptation measures to achieve multiple risk and societal objectives at once.