ProPublica

Journalism in the Public Interest

Cancel

After the Flood

How Well Did FEMA's Maps Predict Sandy's Flooding?

By Al Shaw, ProPublica, December 6, 2013

When Superstorm Sandy struck New York and New Jersey last year, the accuracy of FEMA’s flood-risk maps for the area varied widely. In some cases, the data behind the maps dated as far back to the 1970s. The maps help guide development and set flood insurance rates, so many property owners were left unprepared for the flooding. Click a county below to see more about FEMA’s data for that county, including the age of its maps and how well they predicted Sandy’s extent. | Related story »

  • 98 Gloucester, N.J.
  • 98 Camden, N.J.
  • 92 Ocean, N.J.
  • 89 Nassau, N.Y.
  • 83 Bergen, N.J.
  • 80 Hudson, N.J.
  • 80 New York, N.Y.
  • 79 Middlesex, N.J.
  • 76 Monmouth, N.J.
  • 75 Suffolk, N.Y.
  • 72 Bronx, N.Y.
  • 67 Richmond, N.Y.
  • 54 Queens, N.Y.
  • 47 Kings, N.Y.
  • 37 Essex, N.J.
  • 33 Union, N.J.
  • N/A Atlantic, N.J.
  • N/A Salem, N.J.
  • N/A Burlington, N.J.
  • N/A Cape May, N.J.
  • N/A Cumberland, N.J.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Bergen
Hudson
Essex
Union
Middlesex
Monmouth
Ocean
Atlantic
Cape May
Burlington
Cumberland
Salem
Glouchester
Camden
New York
Bronx
Richmond
Kings
Queens
Nassau
Suffolk
Atlantic Ocean
 
Demers legend County population
  Flood maps predicted 80-100% of Sandy flood area
  Flood maps predicted 40-79% of Sandy flood area
  Flood maps predicted 0-39% of Sandy flood area
  County doesn't have digital flood maps yet

Notes: In certain places on this map, Sandy was such a rare storm that FEMA could not necessarily have predicted all of the areas that would flood. This explains some, but not all, of the variation in these scores. However, areas with newer maps using newer technology predicted the flood extents far more accurately overall. Also, a FEMA official told ProPublica that the accuracy of the inundation maps may vary from location to location, but overall it represents a “very accurate overall depiction of the extent of flooding from Sandy.” Read our methodology »

Sources: FEMA National Flood Hazard Layer, FEMA Modeling Task Force (MOTF) Hurricane Sandy Impact Analysis