Quantifying the effects of employing multiple disaster risk reduction strategies in a coastal flood risk context on the global scale

Coastal flood risk is a major global challenge facing current and future generations. Indeed, this risk is expected to increase over the next several decades due to the changing climate, increased urbanization within flood-prone areas, loss of natural coastal defenses, and underground resource extraction, among other global factors. A number of risk reduction strategies have been posited as methods of mitigating the deleterious impacts of coastal flooding and investigated thoroughly through several existing small-scale applications around the world.

On the global scale, however, efforts to model the effects of such risk reduction strategies in the future are rather limited. Most global modeling efforts that have been undertaken typically examine the potential risk reductions of structural measures (e.g., dykes and levees). And while some initial progress has been made in recent years on assessing alternative risk reduction strategies, the majority of this work still looks to quantify the effects of individual strategies alone. In reality, the hybridization of risk reduction strategies may be the most cost effective or environmentally feasible pathway forward for different segments of society.

We look to quantify the risk reductions expected from employing multiple strategies at once. Within the same global flood risk modeling framework, we model the dry-proofing of urban assets, restriction of future development within flood-prone zones, and conservation of foreshore vegetation. In addition to modeling these strategies individually, we determine what risk reductions are possible when they are hybridized, both with each other and also structural measures. By using a disaster risk framework – risk defined as a product of hazard, exposure, and vulnerability – and a benefit-cost analysis that measures financial and human impacts of each strategy, we determine expected levels of risk reduction for different regions of the world. These results are available for various points in the future under various representative concentration pathway and shared socioeconomic pathway combinations. Further, we demonstrate which (combinations of) strategies may be able to achieve similar levels of overall risk reduction that would be anticipated with solely structural measures. This work not only demonstrates how the envelope of potential options can be expanded for decision makers addressing coastal flood risk, but also can be used as the foundation of future risk flood reduction assessments that incorporate more options than those examined here.