Flood Risk Intelligence
September 6, 2021

Event footprints of Hurricane Ida

Hurricane Ida made landfall near Port Fourchon, Louisiana as a Category 4 major hurricane at 16:55 UTC (11:55 local time) on Sunday, August 29. Maximum sustained wind speeds were estimated to be 150 mph (240 km/hr) producing coastal storm surge and wind damage along the northern Gulf Coast. On Wednesday 1st September intense precipitation affected cities along the mid-Atlantic U.S. coastline.

Fathom have created an event footprint for the mid-Atlantic precipitation event using simulations based on observed rainfall accumulations from NOAA and river gauges from the USGS. As ever, there is more uncertainty with the pluvial coverage away from the main rivers as we don't have detailed information about exactly how the rain fell, as we used 24-hour rainfall accumulations for the analysis.

We would like to share this event footprint with you as you may find it of interest. To download the data file free of charge for your own internal analysis, please contact us. Please note, that this data cannot be used for commercial use*.

Flood footprint of Manhattan

Simulated floods versus satellite imagery: New Jersey

Comparison with remotely sensed imagery from New Jersey indicates that the model has performed relatively well by comparing our event footprint to satellite imagery captured for the event.

About the data

The event magnitude can be considered as unprecedented, with the largest recorded flows on multiple river gauges with records going back more than 100 years.  

These events have been rapidly simulated with no event calibration or validation therefore significant uncertainties will exist in the data.

The data layer itself is called 'Ida_NE_fooprint_DATA.tif'.  It is WGS84 projected, 1 arcsecond (~30m) resolution, with maximum simulated depth in cm.  A value of '9999' is used to represent permanent water.

Get in touch with our team to download the data for free.

Please note, if you do use the data for analysis or validation we would welcome your feedback on the dataset. You can do this, by visiting our contact page or by emailing us.

*By downloading the flood footprint you agree that Fathom does not warrant that the data layer is accurate, complete, reliable, secure, useful, fit for purpose or timely; or the data layer has been tested for use by you the recipient or any third party or that the Data will be suitable for or be capable of being used by you or any third party and that Fathom shall not be liable for any loss whatsoever from the use of this data.

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