Evaluating Flood Resilience Strategies for Coastal Megacities

Publication Type: 
J.C. Aerts
W.J. Botzen
K. Emanuel
N. Lin
H. de Moel
Erwann O. Michel-Kerjan
Recent fl ood disasters in the United States (2005, 2008, 2012); the Philippines (2012, 2013); and Britain (2014) illustrate how vulnerable coastal cities are to storm surge fl ooding ( 1). Floods caused the largest portion of insured losses among all catastrophes around the world in 2013 ( 2). Population density in fl ood-prone coastal zones and megacities is expected to grow by 25% by 2050; projected climate change and sea level rise may further increase the frequency and/or severity of large-scale fl oods ( 3– 7). Despite trillions of dollars of assets located in coastal fl ood-prone areas, investments in protection have often been inadequate ( 8), postponed for short-term economic reasons, for lack of consensus on how to properly evaluate the return on investment, or from the fear of making irreversible choices that become suboptimal over time. To help inform policy decisions, we have developed a multidisciplinary scientifi c approach to evaluate fl ood management strategies. It combines probabilistic risk assessment of hurricanes and storm surge with vulnerability determination of exposed assets at a census level, accounting for sources of uncertainty and the timing of investments in storm-surge fl ood-risk protection. We applied this methodology to New York City (NYC)—one of the most exposed coastal megacities—working with local policy-makers