Building a Robust Hurricane Evacuation Model for Florida
2017’s Hurricane Irma was the largest storm to hit Florida in modern history, causing more than $50 billion in damage and power outages for three-quarters of the state’s population. As the category-five storm approached the southern tip of the peninsula in September, an estimated 6.8 million Floridians were urged to drive north to safer grounds.
Planning for and executing a safe evacuation at this scale was no small feat, and the unfortunate reality of hurricane season in Florida means that emergency management officials face the potential for this challenge annually.
To prepare for these evacuations, the Florida Division of Emergency Management (FDEM), as well as the state’s regional planning councils and county emergency managers, rely on a CDM Smith-developed transportation evacuation model that was created in 2010 under the federally funded Statewide Regional Evacuation Study Program.
The purpose of the tool is to help decision-makers better prepare their communities to undertake evacuations in a safe, orderly and timely manner. The model is powered by two systems: The back-end uses Citilabs’ Cube transportation and land-use modeling platform to evaluate storm scenarios. The front-end is powered by a geographic information system (GIS)-based program known as the Transportation Interface for Modeling Evacuations (TIME).
The TIME interface is user-friendly and is set up for someone who isn’t a modeling expert. TIME lets users select a series of pre-defined conditions to test. They can define time periods to assess, set assumptions about the number of shelters that will be open, and factor in seasonal tourists. They can also edit certain roadway networks to, for example, enable the use of shoulders as emergency lanes.
In the background, the tool pulls from several data sources to run its scenarios: small area data from the U.S. Census and American Community Survey; evacuation zones, developed using storm surge data from the National Hurricane Center; shelter location and socio-economic data, provided by Florida’s counties and regional planning councils; and, the roadway network based on Florida Department of Transportation information.
As an output, the model generates evacuation clearance times for Florida’s regions. These are critical, because they tell emergency planners how much time they’ll need to get people out of dangerous zones. The model also produces estimates for public shelter demand, helping state planners understand where the most vulnerable populations will be during major storms. Between hurricane seasons, emergency managers can update their modeling scenarios to incorporate land use or population changes.
Collaboration and the partnerships fostered between CDM Smith and Florida’s county emergency managers have directly contributed to the model’s efficacy, enabling greater coordination and decision-making between each locality. And as the model has evolved through enhancements over the years, the counties have been better positioned in their planning assumption processes. During Hurricane Irma, for example, the model’s projections for traffic behavior and shelter demands were incredibly close to what occurred on the ground, resulting in a safer and more efficient statewide evacuation.