Exposure of properties to the 2018 Hurricane Florence flooding: an expanding bull's-eye perspective

Abstract. Properly quantifying the potential exposure of property to damages associated with storm surges, extreme weather, and hurricanes is fundamental to developing frameworks that can be used to conceive and implement mitigation plans as well as support urban development that accounts for such events. In this study, we aim at quantifying what was the total value and area of properties exposed to the flooding associated with Hurricane Florence. To this aim, we first generate a map of the maximum flood extent from the combination of the extent produced by FEMA and by means of spaceborne radar remote sensing. Such map is, then, used for estimating the value and area of properties exposed to flooding and the distance of such properties from permanent water bodies. Lastly, we study and quantify how the urban development over the past years and decades over the regions flooded by Hurricane Florence might have impacted the exposure of properties and population to present-day storms and floods, to account what colleagues are starting to address as the “expanding bull’s-eye effect” in which ‘‘targets” of geophysical hazards, such as people and their built environments, are enlarging as populations grow and spread. Our results indicate that the total value of property exposed was $52B, with this value increasing from ~ $10B (2018 USD) from the beginning of the past century because of the expansion of number of properties. We also found that, despite the slowing of property construction in the decade before Florence, much new construction was in proximity to permanent water bodies, increasing exposure to flooding. Ultimately, the results of this paper provide a tool for the understanding of the approaching reckoning that must take place between our continued development in coastal areas and the flooding of those areas, which is estimated to increase because of projected increasing sea level rise, storm surges and strength of storms.