St. Augustine, Florida · NOAA SLR scenarios above MHHW

St. Augustine under rising water

At just 2 ft of sea-level rise, low-lying ground at the Castillo de San Marcos is already under water. At 3 ft, a fifth of the city's land floods beyond today's high-tide line, and the sea reaches the Plaza de la Constitución.

A reproducible pipeline built from NOAA, U.S. Census and OpenStreetMap data. Source code: github.com/Lunarc-Seattle/st-augustine-slr

Drag to compare
01 · Compare

Drag today against the rising sea

The old town today against the same streets after sea-level rise. Drag the handle (or focus it and use the arrow keys), pick a level, press play to watch the water rise a foot at a time, or tap a red ring for a landmark's story. 2.5D view up the bayfront from the south; heights and water exaggerated five times.

The old town at +7 ft: aqua water between white buildings, landmarks in red
+7 ft61.8% of the city's land newly under water
The old town today, dry streets between white buildings
Todayold town at mean higher high water
TODAY +7 FT

05 · Land

New inundation by sea-level rise

Share of the city's 24.63 km² of land that floods at each level, not counting the 5.68 km² (mostly tidal marsh) already below today's mean higher high water. Click a level to see it in the comparison.

1 ft
8.0%
3 ft
21.5%
5 ft
43.3%
7 ft
61.8%
9 ft
69.4%
Ocean-connected (slr) Low-lying, not connected to the ocean (low)
7 of 70OSM historic sites touch inundated land at 3 ft
22 of 31parks touch inundated land at 3 ft
0.14%gap between computed city land and the Census ALAND figure
08 · Figures

Maps and charts, in vector

Figure 1 · A4 landscape · vector PDF 11.9 MB

Inundation at 1, 3, 5, 7 and 9 ft

Five maps of St. Augustine on the same extent and scale. Blue ocean-connected flooding spreads from the marshes and rivers at 1 ft to most of the city at 9 ft.

Same extent and scale on every map. Grey is land already inundated at 0 ft. Blue and orange are new inundation at that level.

Figure 2 · A4 landscape · vector PDF 35 KB

New land loss by level

Stacked bar chart of newly inundated share of city land: 8.0% at 1 ft, 21.5% at 3 ft, 43.3% at 5 ft, 61.8% at 7 ft and 69.4% at 9 ft.

The unconnected low share rises and then falls: as water connects a low-lying area to the ocean, NOAA reclassifies it as slr.

Figure 3 · A4 landscape · vector PDF 5.6 MB

Historic sites and parks at risk at 3 ft

City map and downtown zoom at 3 ft, with historic sites at risk as black triangles and parks at risk hatched green, plus a list of their names.

“At risk” means any part of the site or park touches inundated land. OSM tags many downtown buildings without historic=*, so these counts are a lower bound.

Method

  • City boundary from TIGER/Line 2025, projected to NAD83 / UTM 17N so every area is in m².
  • City land is the boundary minus Census water, so open water never counts as land lost.
  • NOAA slr and low layers are clipped, dissolved and intersected with land at each level.
  • Land already inundated at 0 ft is the baseline; the headline numbers are new inundation only.
  • Every run checks itself: 0 ft new loss is zero, slr never shrinks with level, and slr and low never overlap.

Limits

  • NOAA's layers are a bathtub model on a lidar DEM: no storm surge, waves, erosion or future defences.
  • Whether low areas actually flood depends on drainage and groundwater.
  • The OSM extract is frozen at its query time; site counts are a lower bound.