Assessment of Exposure and Vulnerability to Accelerated Sea Level Rise in New York City

KEYWORDS: sea-level rise, vulnerability, one percent annual flood, New York City Panel on Climate Change (NPCC)

One of the most important climate change impacts is the potential for increased coastal storm surge elevation and extent due to sea level rise. Sea level throughout the 21st century could potentially rise by up to 55 inches in the New York City region by the 2080s according to the IPCC-based and ‘rapid ice-melt' (RIM) climate scenarios developed by the New York City Panel on Climate Change (NPCC). This rise in mean sea level will expose the coastal areas to greater risk as storm surge will be founded upon a higher mean sea level, resulting in potentially greater surge heights and further landward inundation. In order to increase the resiliency of coastal communities to climate change and allow for better identification and response to future coastal hazards, it is important to understand the spatial and temporal impacts of projected sea level rise on coastal flooding regimes and storm surges, their implications for vulnerability, and how this vulnerability will change in this century. This work uses the NPCC city-wide maps that illustrate the potential extent of the future one percent annual flood using the 90th percentile values of IPCC-based and rapid ice-melt (RIM) scenario sea-level rise projections for the 2020s, 2050s, and 2080s and the Cadastral-based Expert Dasymetric System (CEDS) of population disaggregation to determine how many people will be exposed to flooding in New York City through the 21st century. A variation of the New York City Human Vulnerability Index (NYCHVI) derived from Maantay et al. 2009, is used to identify the location and distribution of the socially vulnerable population in current and future flood zones and to determine how this distribution may change through time. Preliminary results show that by the 2080s, one-fifth of the area of NYC could be exposed to the 1% annual flood and that the number of people exposed to flooding may quadruple from 189,000 to 744,000, though these numbers are sure to increase as the population of the NYC region grows. The distribution of socially vulnerable populations in the flood zones appears to mirror the city-wide distribution, with clustered of areas of high and low vulnerability that remain so over time. Additional work will include the integration of several other locally significant variables such as still water elevations and the location of hazardous wastes into the NYCHVI to offer a more refined characterization of exposure that, combined with a social vulnerability assessment, would enable significant improvements in estimating the distribution of at-risk populations and contribute to improved emergency planning and response.