Explanation of Indicator
Prior to the landfall of a hurricane, evacuation orders are given to residents determined to be at risk of death or injury from flooding and high winds. The affected population is determined by a variety of factors including hurricane characteristics, risk attributes associated with residential location, evacuation route, and shelter access. Evacuation time is determined by the number of residents to be evacuated, the expected behavior of those residents, and roadway network characteristics. Evacuation orders are given far enough in advance for the evacuating residents to completely clear the area prior to the arrival of gale force winds.
As evacuation times rise, the coastal population is at greater risk of death or injury during hurricanes. With longer evacuation times, either fewer people can be evacuated within a certain time frame or the evacuation order must be given earlier. When evacuation orders are given early and a hurricane does not make landfall, the public becomes increasingly skeptical of the validity of the orders, which may affect the response during the next order. If the orders are not given earlier, fewer people can evacuate thus placing a greater number of people at risk. Evacuation time is critical to the safety of the public and serves to indicate the potential for hazardous situations. Hurricane Evacuation Study: Technical Data Reports, which are prepared for each regional planning council (RPC) and their member counties, indicate that many of the state’s coastal urban areas have long evacuation clearance times. This may be a problem; however, no consistent information is available to show how these evacuation clearance times are changing from year to year.
The Technical Data Reports contain several different analyses that are necessary to determine clearance times. The hazards analysis contains models showing the storm surge inundation effects of a variety of types of hurricanes. From this, the vulnerability analysis compares those inundation areas to the spatial population distribution to determine the population at risk to various storms. The behavioral analysis assesses how the population reacts to the approach of a hurricane and the issuance of an evacuation order. The transportation analysis combines all these analyses with assessment of the evacuation roadway capacities to determine how long it will take for the population to exit the area.
SOURCE The Hurricane Evacuation Study: Technical Data Reports are available from each regional planing council which conducted the study (in some cases, as a joint effort with other RPCs or other entities) for each county in its jurisdiction. The studies were either conducted by the RPCs or by the Army Corps of Engineers (ACOE) as a contractor. In addition, Chapter 9J-5, section 102(2)e.1 of the Florida Administrative Code requires local governments to inventory and analyze evacuation times in their comprehensive plans. A survey of these plans indicates that this information was based on the Technical Data Reports. Listed below are the RPCs, the preparers of the Technical Data Reports, and the dates of all initial and updated reports.
Regional Planning Council Preparer of Reports Dates of Reports Southwest Florida RPC 1982, 1984, 1987,1991 Withlacoochee RPC 1989 North Central Florida RPC 1985 East Central Florida RPC 1984, 1989 Northeast Florida RPC 1984, 1988 Treasure Coast RPC 1994 Central Florida RPC 1983, 1989 South Florida ACOE 1991 Tampa Bay RPC 1981, 1984, 1988, 1992 Apalachee RPC 1984, 1994 West Florida ACOE 1986
ACQUISITION Hard copies of the Technical Data Reports are available at photocopying expense.
COLLECTION The data have been collected and modeled at varying time periods for all Florida counties.
The data have been collected for varying time periods and are not collected for the same time interval across all counties; this limits trend analysis as well as inter-county comparisons. In addition the methodology and assumptions, although generally consistent, do vary depending on when the study was conducted and by whom the study was conducted. The primary variables include surge inundation areas, population data, storm scenarios, evacuation areas, behavioral characteristics of evacuating populations, and roadway network and traffic control data. Each variable contains many sub-variables, many of which are dependent upon assumptions that have not been universally agreed upon. Moreover, the definition of clearance time is not consistent across all reports.
Because local governments are required to update their comprehensive plan every five years, which necessitates the calculation of updated evacuation times, the regional planning councils should establish a regular procedure for updating the Technical Data Reports. Currently, there is no regular schedule for updating the Technical Data Reports; instead the RPCs or the ACOE has been updating the reports as funding becomes available and as time permits. The Florida Coastal Management Program and the RPCs should work together to establish a regular funding mechanism for these studies.