The Issue: Urban Flooding

More frequent flooding is expected along major rivers and estuaries if sea level rises.

The Strategy: Floodgates

A set of floodgates across the Thames River, London.

Mark Edwards/Peter Arnold Inc.

The Thames River estuary is a major waterway that connects London to the North Sea. Today, a set of six floodgates stretches across the Thames to stop a rising sea from rushing upstream and spilling onto London's streets.

Like any estuary, the Thames River rises and falls with ocean tides. When the North Sea tides are particularly high due to storms, the Thames floods. Some 1.25 million people live in the Thames floodplain in and around London. High retaining walls offer some protection against flooding, but the floodgates of the Thames Barrier keep tidal surges at bay. First used in 1983, the Thames Barrier has been closed more than expected in recent years. Can it withstand rising waters posed by future climate change? London is establishing a flood response plan to address the issue.

Like London, Shanghai is a low-lying city that has suffered severe flooding during storm surges. The government has proposed erecting water gates and a sea wall as methods of holding back high water.