Inside the Line

Providence only. Residents: 2020 Census, by block. Jobs: 2023, LEHD LODES 8, by block. Assessed value and tax billed: the city's 2025 tax roll, each account placed at its mapped point. Inside the line, $1,495M of the $2,807M assessed is exempt. The largest single account in any ring is Providence Place, in the river flood zone: $731M assessed, carried as exempt on the roll, paying the city instead under its 1996 tax agreement. The largest in the coastal ring are Johnson & Wales's Harborside campus, the Providence Public Building Authority at 1 River Dr., and Narragansett Electric on Terminal Road.

Storage tanks mapped in OpenStreetMap: 36 stand in the flood zones outside the line, 5 inside it. Each is matched to the tax-roll lot it stands on.

Inside the line, OpenStreetMap maps the Manchester Street Generating Station and the Franklin Square, Point Street and South Street substations. Outside it, in the flood zones: Green Providence Wind I, Green Providence Wind II, NBC Field's Point Wind Farm. The Fields Point Treatment Plant is in the 500-year zone outside the line. OpenStreetMap is volunteer-mapped; a tank it lacks is not counted.

FEMA maps the barrier's protected area as "area with reduced flood risk due to levee," its label for land behind a levee it credits. The main piece is 279.1 acres; the Army Corps gives "about 280 acres." FEMA credits two more pieces, for 418 acres in all:

Jobs: 14,878, 1,424, 2,280, in the same order. Acres are FEMA's polygons; the other columns use the same sources as the table above. A handful of slivers under two acres each make up the rest.

Share of the ground lower than each water level, inside the line and on the coastal-zone parcels outside it:

Feet above NAVD88. Daily high tide is mean higher high water; the gates close at 7.68 ft above mean lower low water; FEMA's coastal flood elevations outside the line run 12 to 15 ft, and the table uses the low end. Carol (16.5 ft above mean lower low water at the Providence gauge), the design storm (22.18) and the top of the barrier (26.68) are from the Coastal Resources Management Council's Metro Bay plan, January 2009 draft; the Corps' own design drawings are requested. Median ground: 11.9 ft inside the line (418 acres), 8.3 ft on the 266 acres of coastal-zone parcels outside it. Ground from 5-ft contours of the 2011 Northeast LiDAR, interpolated on a 20-ft grid; water levels from NOAA gauge 8454000, converted from mean lower low water (NAVD88 sits 2.47 ft above it at the gauge).

The same storm on a higher sea

Share of the ground lower than Hurricane Bob's peak, raised by the Corps' sea-level curves:

Rise measured from 2016.5, the same curves as the projections below. Inside the line, these are the levels the barrier is there to hold out; its top is 24.2 ft.