Sandy's Sequel Plays on a Higher Stage
Replay Hurricane Sandy on the seas projected for 2100 — up to 5.4 ft higher — and the surge crests 16.7 ft, drowns Wall Street under 3.7 ft, and bills the city $43B.
Sandy's water topped out at a number New Yorkers remember. Run the same storm on the harbor projected for 2100, and the still-water flood height reaches 16.7 ft on the NAVD88 vertical datum — the surveyor's reference for "how high above the ground" — which is 14.4 ft above today's high tide.
That extra elevation is sea-level rise doing the work before the storm arrives. The New York City Panel on Climate Change (NPCC) puts the rise at up to 5.4 ft by 2100. The storm is the same; the floor it starts from is higher.
The depths read like a tour of the waterfront. South Street Seaport sits under 13.7 ft of water, Red Hook under 11.7 ft, The Battery under 10.7 ft. LaGuardia Airport takes 9.7 ft, Rockaway Beach 8.7 ft, Coney Island 6.7 ft, JFK Airport 4.7 ft, and Wall Street 3.7 ft.
Notably, the rain is the small player here. The peak rate is 1.0 in/hr against sewers built for 1.75 in/hr — comfortably within capacity. Over roughly 8 hours that totals about 3 inches, modest beside Ida's 7 inches and only triple Sandy's roughly 1 inch.
So the damage is a surge story. The estimate runs about $43B — more than double the roughly $19B Sandy actually cost. The water comes from the harbor, not the sky.
Four places don't need a storm at all. At this sea level, South Street Seaport, Red Hook, The Battery, and LaGuardia Airport flood at ordinary high tide — chronic 'doomed' zones, wet on a calm day with no hurricane in sight.
That reframes the bill. A harbor surge barrier would cost $52.6B and stop the surge — but not the rain, and not the daily tide already standing in four neighborhoods. The $43B storm is the loud problem; the quiet one is the high tide that never leaves.