Hurricane Idalia: Tracking Evacuations and Population Movement


Hurricane Idalia

Idalia's path as mapped alongside, social vulnerability statistics, population movement, and infrastructure. (CrisisReady)

Editor’s note: This post was originally published by CrisisReady, a collaborative initiative of Harvard University and Direct Relief.

Hurricane Idalia made landfall at Keaton Beach in Florida’s Big Bend as a Category 3 storm at 8 a.m. ET on August 30th, 2023. The storm had been downgraded from a Category 4 but still maintained winds of 125 mph.

The impact of the storm has resulted in flooded streets, closed airports, canceled flights, and widespread power outages.

The National Weather Service in Tallahassee warned that certain locations might be uninhabitable for weeks or even months due to wind damage and storm surge barriers.

CrisisReady, a joint effort of Harvard University and Direct Relief, is creating situation reports to inform relief efforts. These reports analyze anonymized and aggregated data on the movement of Facebook users to track changes in population densities, highlighting displacement in affected areas of Florida. They also contain information about baseline population vulnerabilities and local healthcare infrastructure, such as facilities, outpatient centers, and hospitals.

The report below provides data on population density changes in northern and central Florida as of 7:00 p.m. local time on Tuesday, August 29, 2023, the evening prior to Hurricane Idalia’s landfall. It highlights population displacement during the period evacuation orders were issued by state and county officials.

Additionally, the report provides information on baseline population vulnerabilities and the status of local healthcare infrastructure.

Key Observations

Counties with Population Decline Prior to Landfall

Predominantly in the Big Bend and inland areas:

  • Madison
  • Suwanee
  • Levy
  • Lafayette
  • Wakulla
  • Echols
  • Dixie
  • Taylor
  • Franklin

Counties with Significant Declines

Coastal regions with declines of 10% or more where evacuation orders were issued:

  • Dixie
  • Taylor
  • Franklin

Areas registering population drops of 45% or more before the storm:

  • Panacea
  • Steinhatchee
  • St. Mark’s
  • Crystal River
  • Homosassa

Note: Steinhatchee reported storm surge levels over 8 feet as of the morning of August 30th, indicating extreme risk.

Social Media Usage & Mobility Data:

Florida communities in the Big Bend area typically exhibit:

  • High Facebook usage rates with location services (15%-25%).
  • Consequently, there is a high degree of representativeness in mobility data.

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