AP IMPACT: Defending NYC from effects of next surge requires many changes, difficult choices

If metropolitan New York is going to defend itself from surges like the one from Superstorm Sandy, decision makers can start by studying how others have fought the threat.

Experts say that while many cities have learned much about how to control damage from flooding, there is no cure-all. The Associated Press explored some strategies that have been used.

Here are some examples:

— Tunnels under a Houston medical campus have 100 submarine doors ready to block invading floodwaters.

— Bangkok commuters must climb three feet of stairs to raised subway entrances equipped with flood gates.

— And in Washington, managers of a retail and apartment complex need just two hours to activate steel walls designed to hold back as much as a 17-foot rise in the Potomac River.