An Ounce of Prevention

When it comes to hurricane preparedness, the old saying, "an ounce of prevention is worth a pound of cure," rings true—especially for evacuation strategies. A new study for New York City considers the unique scenario of moving a large population without cars in a densely inhabited area.

"When most individuals think of hurricanes, they think of the southern states and their exposure to the tropics. In reality, hurricanes pose a very serious threat to northern states, especially New York," says Don Lewis, PBS&J vice president and manager of the company's Evacuation Planning Division. "The effects of a major storm in the five boroughs of New York City—Manhattan, Brooklyn, Queens, Staten Island, and the Bronx—could be catastrophic."

Probability scientists put a hurricane in the area's future. There is a 21-percent chance that New York City/Long Island will be hit with a tropical storm or hurricane in 2007. And there is a 26-percent probability that New York City/Long Island will be hit with a major hurricane (Category 3 or more) in the next 50 years.

If another Long Island Express were to barrel in, says AIR Worldwide Corporation, an insurance-industry analyst, New York would suffer $11.6 billion in losses alone. On AIR's list of "the top ten worst places for an extreme hurricane to strike," New York City is second only to Miami.

A Fresh Look at Evacuation

Given these statistics, the lingering images of a Katrina-devastated New Orleans, and forecasts of an active hurricane season, New York City officials and the U.S. Army Corps of Engineers (USACE), New York District, initiated a hurricane evacuation restudy for the five boroughs. The District, working in conjunction with the Federal Emergency Management Agency Region 2 and USACE Wilmington District, hired PBS&J to perform the tasks necessary to update the area's hurricane evacuation clearance times.

The restudy's multiple objectives included quantifying the potential evacuation population using socioeconomic and behavioral data, identifying the existing evacuation roadway network, and developing hurricane evacuation clearance times for an existing base year. In addition, the restudy would help to determine regional evacuation traffic that could be expected to cross county lines and move inland, and to identify bottlenecks and key roadway segments.

Some of New York's challenges to lifesaving evacuation: many residents live in low-lying areas; fewer than half of all households own cars; almost half of Manhattanites over age 65 are disabled; the city exceeds the national average in families below the poverty level; the area is heavy with tourists and business visitors; and roadways are extremely congested even under clear blue skies.

Considering Mass Transit and Public Shelters

PBS&J's solution was to develop a model that incorporates the heavy use of mass transit for peoplemoving, with public shelters as the final destination for many of the evacuees. "This is the first of its kind," says Lewis.

The Abbreviated Transportation Model (ATM) includes modules to accept a variety of input: socioeconomic data, behavioral data, evacuation statistics, and out-route percentages. The New York model also accepts vehicle ownership statistics and mass transit zone data. Output is presented in a spreadsheet format that includes information about evacuating vehicles by zone and by bottleneck, evacuation clearance times, and both mass transit and public shelter demands.

"We identified the 'car-less' population geographically and established a half-mile 'walking' radius for them to reach evacuation hubs," Lewis elaborates. "From the hubs the city would assign people to specific shelters. The people with cars were appropriately assigned to out routes and not included in the shelter assignments."

Changing Parameters to Hone Projections

The added value of ATM lies in its ability to project what-if scenarios. A huge amount of demographic, geographic, and behavioral data resides in its default outputs, wherein recommendations are presented for specific storm conditions. However, areas within the modules allow managers to change parameters. By manipulating storm surge and census information in individual zones, for example, users can develop more precise projections.

"Hurricane Katrina brought the evacuation of populations without vehicles to the forefront of public discourse," says Lewis. "New York City took the lesson to heart." Now, with a modernized evacuation plan, the city can prepare for the worst. And in the meantime, Lewis says the ATM will be used for response to the more frequent coastal storms.