Debris littering the streets of Tacloban on November 14, nearly a week after the storm struck. (PHOTO: TROCAIRE/WIKIMEDIA COMMONS)

We still don't have a reliable body count from Tacloban, the Philippines city hardest hit by Typhoon Haiyan, but it's certainly in the thousands. That's a horrific statistical ballpark—and such casualty counts are all but certain to continue rising in future storms all over the world. One reason, of course, is that climate change is exacerbating the intensity and frequency of catastrophic weather. But there's another, much less remarked-on reason why such disasters kill so many people: the massive population growth in coastal cities around the world. Simply put, there are more people in harm's way all the time.

Shoddily-constructed buildings thrown up in a hurry to house all those newcomers also tend to fall down when the going gets rough.

Basically, as the world's population continues to grow, more and more people are heading for the most economically attractive places, which tend to be cities, which tend to be along coastlines. That's why the number of people living in Tacloban has tripled in recent decades, from 76,000 in 1970 to more than 220,000 when the storm hit. Obviously, that puts three times as many people at risk of being killed when disaster strikes. But population growth compounds risk in other ways. All those people drawing water from underground aquifers can cause the already low-lying land to sink further. That's probably part of the reason so much of Tacloban sits below sea level, a fact which makes the city even more vulnerable to flooding. Shoddily-constructed buildings thrown up in a hurry to house all those newcomers also tend to fall down when the going gets rough.

Despite those dangers, no one expects the migration to coastal areas to stop. By 2050, the United Nations estimates some six billion people will be living in such areas. Where to worry about most? Here's a handy list of the 20 cities most at risk from storms and flooding, courtesy of Bloomberg.