After Sandy: Rethinking Flood Risk Management in Asian Coastal Megacities

The tropical storm, and for a time hurricane, named Sandy arrived on the U.S. east coast on October 30, 2012, and delivered a 5.1-m storm surge, the highest since 1851, to the heart of the country’s financial hub in the Lower Manhattan area of New York City (NYC) (Fig. 1) [National Oceanic and Atmospheric Administration (NOAA) 2012]. As a result, there were more than 40 fatalities across the city, and the storm-related death toll across the northeast United States reached 63. Sixty-nine deaths in the Caribbean region meant that the total number of casualties caused by the storm was 132 [British Broadcasting Corporation (BBC) 2012; Fischetti 2012]. Public transport systems were submerged, the runways of two major airports (John F. Kennedy and Newark) were flooded and closed, and the New York Stock Exchange was shut down for 2 days. The forecasting firm Equcat estimated the likely total cost of damages to be more than $85 billion (Reuters 2012b). Reuters estimated damage of at least $18 billion in the area between downtown and Long Island alone (Reuters 2012a). To put this in context, the average annual losses from cyclones, storm surges, coastal floods, and winds in the United States are estimated to be in the region of just $10 billion per year. Although the magnitude of Sandy was less intense than Katrina in 2005, Sandy affected a larger area; the National Aeronautics and Space Administration (NASA 2012) reported strong winds (greater than 65 km=h) for a distance of approximately 500 km during Hurricane Katrina, whereas Sandy prevailed for over 1,500 km at a similar intensity. This is possibly the main reason why Sandy generated sea surges over a larger coastal area than did Katrina, and affected more than 12 states on the east coast [China Central Television (CCTV) 2012]. Previous research (Webster et al. 2005) has indicated that the frequency and intensity of cyclones (i.e., hurricanes and typhoons) has increased in the past 50 years, and that the trend is expected to rise continuously this century because of climate change. The Intergovernmental Panel on Climate Change (IPCC 2012) also reported that it is likely that there has been a poleward shift in the main Northern Hemisphere extratropical storm tracks, which means that the potential for intense storms that produce significant wind and extreme rainfall is slightly increased. The impact of Storm Sandy reflects the vulnerability of coastal megacities across the globe. This vulnerability exists because human settlement, including properties and infrastructure, is located mostly in low-lying flood-prone areas similar to those of New York City. The major financial hub of Wall Street, for example, is just a mile away from the harbor. An accepted definition of a megacity is a city with a population of 8 million or more (United Nations 2010). NYC has 8.2 million inhabitants, approximately 2 million of whom live on Long Island or smaller islands and in flood-prone areas. The city government realized that it would be impossible to relocate this number of people and associated assets outside of the hazard areas, and has therefore started to adapt flood-management strategies in preparation for climate change (NYC Government 2012). Adaptation practices such as assessment of surge risk, flood-risk mapping, prediction of risks from various climate scenarios, and enhanced emergency evacuation plans have been implemented since 2010 (Klima et al. 2011). The city’s storm warning system was activated some 41 h before Storm Sandy arrived, at which point city authorities announced the closure of the financial markets and advised residents to stock up on food and water. Recommendations to employ sandbags for flood