SEATTLE — People in Boise, Idaho, have taken pride in favorable lifestyle rankings their city has picked up recently: No. 2 on Forbes' best places for business and careers; No. 9 on Inc.com's hottest cities for entrepreneurs; No. 1 National Geographic adventure town; and No. 8 on Money magazine's best places to live.
But one title startled and baffled nearly everyone: city most vulnerable to terrorism in the Western United States.
In a study funded by the Homeland Security Department, Idaho's state capital was the only Western city in the top 10 among 132 urban centers ranked by vulnerability based on a unique mathematical calculation.
The top five seemed logical: big cities with exposed ports and bridges. The list reads like a who's who of Eastern and Southern port cities: New Orleans; Baton Rouge, La.; Charleston, S.C.; New York City-Newark, N.J.; and Norfolk, Va.
Not a single West Coast city, from Seattle to San Diego, raised more than an eyebrow.
Juneau, Alaska, ranked least vulnerable.
Out West, at No. 10, stood landlocked Boise, population about 200,000, nicknamed the City of Trees.
"It surprised us too," said researcher Walter W. Piegorsch, a mathematics professor at the University of Arizona, coauthor of "Benchmark Analysis for Quantifying Urban Vulnerability to Terrorist Incidents."
The report, which relies on a complex formula for a "place-based vulnerabilities" score, first appeared in December in the journal Risk Analysis. Communities it identified have since been trying to absorb its meaning.
Scores depended on three main considerations: social demographics, natural hazards (floods, wildfires, earthquakes, extreme weather, etc.) and infrastructure vulnerability (roads, bridges, tunnels, ports, dams, skyscrapers, etc.).
Boise, it seems, faces high risk from extreme events such as wildfires or failure of a large dam upstream, Piegorsch said. Seventeen miles northeast of Boise, Lucky Peak Dam extends 2,340 feet long and 340 feet high. The 12-mile-long reservoir behind it stores 300,000 acre-feet of water.
"That dam could be a very likely target, or possible target," he said, noting that Boise's recent experience with disaster, flooding, property loss and casualties also elevated its rank.
The index says more about experience and ability to cope than about where terrorists might strike, Piegorsch said.
"You can't predict the next terrorism," he said. "That's why it's terrorism. But you can predict vulnerability."
The high vulnerability rating stunned Idaho law enforcement and emergency management agencies.
"Everybody was surprised," said Charles McClure, a spokesman for the Boise Police Department. "Basically, we don't understand how they arrived at that conclusion."
Idaho officials are working with the FBI and the study's authors to determine if the findings can lead to improved procedures, said Lt. Col. Tim Marsano, spokesman for the Idaho Bureau of Homeland Security.
"It raised some flags among the emergency management community within this state, and we are taking it seriously," Marsano said. "We hope to pull things out of it that will further enhance our preparedness."
Co-written by Susan L. Cutter at the University of South Carolina and Frank Hardisty at Pennsylvania State University, the research investigated relationships between vulnerability and terrorist outcome.
The project, four years in the making, crunched data from 1970 through 2004 related to natural or man-made disasters and hazardous events, including terrorism. The data boiled down to a single place-based vulnerability index.
The index borrowed from statistical methods used in research involving identifying cancer-causing substances. The National Cancer Institute funded part of the study.
Researchers assigned the cities threat-level color codes: green (low), yellow (medium) and red (high).
A swath of red cities stretched from Houston up to New York. Several cities in the Carolinas (Raleigh/Durham, Charlotte, Charleston and Columbia) were red.
On the West Coast
Most cities in the West and North were yellow or green. Western localities, in general, covered more land. ("Once you sprawl, you lower vulnerability," Piegorsch said. "You can't hit a less concentrated location as effectively.")
California cities scored reasonably well (none were red) in part because their infrastructures have already been hardened, the researchers said. San Francisco (yellow) shares traits of higher vulnerability with Eastern cities -- ports, bridges, skyscrapers and a high-density urban area -- but repeated disasters have actually led to higher rankings because the Bay Area has focused on constructing safer buildings and taking other preparedness measures.
"San Francisco has had earthquakes, but emergency response has improved because of it," Piegorsch said.
Los Angeles and San Diego, both yellow, benefited from experience as well as being geographically spread out.
'What are they missing?'