Vulnerability of megacities: case study of New York City
New York City faces increasing vulnerability to flooding and storm Even modest increases in sea level can exacerbate flood risks. An
surges as sea level rises, with extensive damage to infrastructure earlier study found that by the 2080s flood heights of today’s 100-
and buildings, beach erosion, and loss of wetlands. Within the year storm (including both hurricanes and powerful nor’easters)
last 45 years, at least three coastal storms have produced wide- would be more likely to recur, on average, as often as once in
spread inundation and disruption of area transportation systems. 60 to once in every 4 years, and that beach erosion rates could
Major portions of the city’s transportation infrastructure lie at el- increase several-fold, with associated sand replenishment needs
evations of 3 m or less and have been flooded by severe storms increasing 26 per cent by volume
78,79
.
in the past. Regional beaches and coastal wetlands, which pro-
vide recreation areas and buffer zones against destructive storm New York City is especially vulnerable to major hurricanes that
surges, have been eroding, due in part to historic sea-level rise travel northward along a track slightly to its west, since the strong-
and to the presence of “hard” engineering structures. est, most destructive winds to the right of the hurricane’s eye
would pass directly over the city. Furthermore, the surge would
Regional 20th century rates of relative sea-level rise (2.1 to 3.8 mm be funnelled toward the near right-angle bend between the New
per year) lie above the global mean trend as a result of subsidence Jersey and Long Island coasts into the New York City harbour.
caused by ongoing glacial isostatic adjustments. Recent projec- The city and surrounding areas have experienced at least three
tions of sea-level rise range between 29 and 53 cm for New York Category 3 hurricanes during the 20th century. Adding as little as
City by the 2080s, depending on model and emission scenarios 47 cm of sea-level rise by the 2050s to the surge for a Category
used
77
. Increased ice sheet melting or break up would augment 3 hurricane on a worst-case storm track would cause extensive
these model projections. flooding in many parts of the city
80
(Figure 6C.14).

(a) (b)
Figure 6C.14: New York City, storms and flooding.
(a) Flooding on the FDR Drive and 80th Street, Manhattan, looking north, during the December 13 1992 extra-tropical cyclone.
(b) Calculated potential surge height (with present day sea level) for a Category 1 (Saffir-Simpson scale) hurricane at Brooklyn-
Battery Tunnel Manhattan entrance.
Source: (a) The Queens Borough Public Library, Long Island Division, New York Herald-Tribune Photo Morgue; (b) Rosenzweig and Solecki 2001
79
174 GLOBAL OUTLOOK FOR ICE AND SNOW
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