National Geographic : 2013 Sep
program of dike and barrier construction called the Delta Works, which lasted more than four decades and cost more than six billion dol- lars. One crucial project was the five-mile-long Oosterscheldekering, or Eastern Scheldt bar- rier, completed 27 years ago to defend Zeeland from the sea. Geluk points to it as we stand on a bank of the Scheldt estuary near the museum, its enormous pylons just visible on the horizon. The final component of the Delta Works, a movable barrier protecting Rotterdam Harbor and some 1.5 million people, was finished in 1997. Like other primary sea barriers in the Neth- erlands, it’s built to withstand a 1-in-10,000-year storm—the strictest standard in the world. (The United States uses a 1-in-100 standard.) The Dutch government is now considering whether to upgrade the protection levels to bring them in line with sea-level-rise projections. Such measures are a matter of national secu- rity for a country where 26 percent of the land lies below sea level. With more than 10,000 miles of dikes, the Netherlands is fortified to such an extent that hardly anyone thinks about the threat from the sea, largely because much of the protec- tion is so well integrated into the landscape that it’s nearly invisible. On a bitingly cold February afternoon I spend a couple of hours walking around Rot- terdam with Arnoud Molenaar, the manager of the city’s Climate Proof program, which aims to make Rotterdam resistant to the sea levels expected by 2025. About 20 minutes into our walk we climb a sloping street next to a museum Ryan moRRiS, ngm Staff. SouRceS: felix landeReR, naSa/Jpl; m. peRRette et al, 2013; oRganiSation foR economic co-opeRation and development +4 ft Exposed assets Exposed population $3 trillion or more $2-2 .9 trillion Up to $2 trillion 14 million or more 10-13 million Up to 10 million 0 Sea-level drop 2 4,1 Kolkata (Calcutta) Dhaka 3 Ho Chi Minh City 5 Mumbai 2 (Bombay) Shanghai 5 New York 3 Miami 1 Guangzhou 2, 4 Sea-level rise (by 2100) Top five cities most at risk from rising seas (by 2070) Rank (1-5) as the sea warms and pulls back from dwindling ice sheets, it rises most in the tropics. near a melting ice sheet, sea level falls— as the ice’s shrinking gravity no longer pulls the sea toward it as much, and as the land underneath rebounds. Rapidly sinking land worsens flooding in river- delta cities such as calcutta, dhaka, and ho chi minh city. Uneven Impacts if sea level rises an average of around three feet by 2100, winds, currents, and melting ice sheets will distribute the rise unevenly. certain coastal cities will be especially vulnerable.