Rainfall from Hurricane Ian floods Florida

Hurricane Ian hit Florida on September 28, 2022 as a Category 4 hurricane. Ian’s eye made landfall first on Cayo Costa island around 3:00 pm EDT [1] and on the Florida mainland south of Punta Gordo near Pirate Harbor around 4:30 pm EDT [2]. The National Weather Service’s National Hurricane Center 5:00 pm EDT advisory [3] reported “catastrophic storm surge, winds, and flooding,” maximum sustained winds of 140 MPH, and storm surge up to 18 feet above ground level near the coast. The storm made a historic impact along the coast from south of Marco Island to North of Port Charlotte, leaving areas like Fort Myers Beach devastated [4].

Ian’s path crossed the Florida Peninsula to the south of Orlando and into the Atlantic near Cape Canaveral. Inland areas weren’t spared. As of September 30, the Federal Emergency Management Agency (FEMA) was reporting 18 Florida rivers at major flood stage and 16 more at minor or moderate flood stage [5]. Many Florida rivers reached record levels between September 28 and 30, and excess flooding in slow-draining areas continued for weeks.  

AER’s FloodScan system automatically maps large-scale inland flooding across North America, Africa, and South America from cloud-penetrating passive microwave satellite observations. Image 1 shows FloodScan’s Maximum Daily Flood Extent Depiction product (MFED) as it first mapped flooding on September 29. Image 2 uses FloodScan’s daily flood mapping capabilities to show all the areas found to be flooded between September 29 and October 17. Image 3 shows FloodScan’s maximum flood depth estimates for the same period.

A GIS-compatible package of the complete FloodScan product suite covering Ian’s impact on Florida is available for purchase through the AER store.

Image 1: FloodScan’s view of flooding on September 29, one day after Ian’s landfall. 

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Image 2: Composite flood map using FloodScan data from September 29 to October 17. The green line is the track of Hurricane Ian.

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Image 3: Maximum FloodScan flood depth map from September 29 to October 17. The green line is the track of Hurricane Ian.

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As of October 26, AER’s experimental FloodLoss algorithm estimates that flooding from Ian affected 473,273 buildings statewide with associated damages ranging from USD 19 billion to USD 234 billion (USD 127 billion median). For comparison, Verisk estimates that total insured losses to onshore property from Hurricane Ian will range from USD 42 billion to USD 57 billion [6]. FloodLoss combines FloodScan data with data from the Microsoft Building Footprint Database [7] to algorithmically assess the number and size of flooded buildings. Real estate valuations and historical National Flood Insurance Program (NFIP) Data [8] are used to assign loss values. The FloodLoss estimate of total loss includes only flood-affected buildings and not losses due to wind, storm surge, and other non-flooding mechanisms.

[1] https://www.nhc.noaa.gov/archive/2022/al09/al092022.update.09281909.shtml?

[2] https://www.nhc.noaa.gov/archive/2022/al09/al092022.update.09282035.shtml?

[3] https://www.nhc.noaa.gov/archive/2022/al09/al092022.public.025.shtml?

[4] https://www.nytimes.com/interactive/2022/09/29/us/hurricane-ian-flooding-fort-myers-florida.html

[5] https://content.govdelivery.com/attachments/USDHSFEMA/2022/09/30/file_attachments/2284776/FEMA%20Daily%20Ops%20Briefing%2009-30-2022.pdf

[6] https://www.verisk.com/newsroom/verisk-estimates-industry-insured-losses-for-hurricane-ian/

[7] https://www.microsoft.com/en-us/maps/building-footprints

[8] https://www.fema.gov/openfema-data-page/fima-nfip-redacted-claims




Senior Manager Verisk AER Science