Do You Know Your City’s Natural Catastrophe Risk?

Hurricane Ike flooded major portions of North America. Photo: Noel Hankamer, Flickr 

It is no surprise that natural catastrophes pose a major risk to our urban centers. In fact, according to the Swiss Re Sigma 2014 report, natural catastrophes resulted in around $131 billion U.S. in economic loss in 2013. That’s nearly $20 in loss for every person in the world.

One thing everybody wants to know is if they and their city are actually prepared for the next major shock, whether it’s earthquakes, tornados, floods, or something more man-made. To get to the heart of that question, we wanted to look at what risks cities are prioritizing to drive their preparation. In other words, “Does my city know what to be prepared for?”

100 Resilient Cities has data from cities’ 2013 Challenge applications that gives us an interesting angle on this question. During last year’s challenge, we asked cities who wanted to join 100RC to submit applications that included a detailed self-analysis of their biggest threats. Our applicant pool represented almost 400 cities and a total of 545 million people. In order to find out if the cities know what to be prepared for, we compared their self-analysis  data, to hazard data from Swiss Re’s CatNet®. Cat Net® is an information tool that includes, among other things, a wealth of data about cities’ exposure to natural hazards–earthquakes, floods, atmospheric and other perils—all overlaid on Google Maps to create a picture of cities’ risk.

Flooding tells the most interesting story. Of the several hundred cities that applied in the first round, about 60% of the cities listed flooding in their application. It was initially surprising that nearly a full two thirds of applicants listed flooding as their biggest or one of their biggest threats. However, according to CatNet® nearly 85% of the cities are in fact exposed to significant coastal or river flooding. Flooding was actually underrepresented in applications.

Next to flooding, the most frequently listed natural catastrophe exposure was earthquakes. About 30% of applicant cities are exposed to “significant earthquake risk,” defined as considerable damage to ordinary buildings, with heavy furniture overturned. Yet only about 15% of the applicants mentioned earthquake as a threat, again showing and underrepresented hazard.. And another handful of cities from the first round have a high earthquake exposure (meaning that most masonry and frame structures could potentially be destroyed), but did not identify earthquakes as one of their major risks. As with floods, several cities overstated their exposure to earthquakes.

The third most common natural hazard from last year’s applicants was tropical cyclones/extreme wind exposure. About one in three cities from the first round is exposed to high wind while about half this number mentioned extreme wind as a concern. Our analysis also found that a significant number of applicants are exposed to hail and tornados, while few listed these threats as a concern.

Some regional differences in risk perception also turned up. For example, about 32% of the applicant cities in South America that have a significant exposure to earthquakes failed to mention this risk, versus about 12% of North American cities with similar risks. Although the general trend was to underestimate flood exposure, 80% of European cities included flood exposure in their applications.

The picture our analysis painted was of cities that generally have a good sense of their risk exposures; however, despite how many ranked earthquakes and flooding as significant concerns, it was still fewer than how many should have.,

Joshua Woodbury, PhD, is an associate with Swiss Re, but prepared this work while seconding with 100 Resilient Cities.


Header Photo, DFID, Flickr