Sea-Level Rise at Timucuan Preserve, Florida: Most of the Park Likely Flooded by 2050

National parks and preserves in the South Atlantic-Gulf Region hold valuable coastal habitats — tidal wetlands, mangrove forests — and irreplaceable historic buildings and archeological sites on low ground. All are vulnerable to accelerating sea-level rise (SLR) and more frequent high tide flooding (HTF).

In a project funded by the NPS Natural Resources Preservation Program in 2021–23, the U.S. Geological Survey (USGS) and the National Park Service estimated the probability of inundation at Timucuan Ecological and Historic Preserve (TIMU) and several other parks, under several sea-level scenarios and today's high tide flooding thresholds.

The preserve

TIMU is in Jacksonville, Florida, on the southern Atlantic coast, and covers 145.35 square kilometers of land. Most of it is coastal wetland, specifically salt marsh. Such habitats survive rising seas only if they can build up in place or move to higher ground — tidal marsh transgression. Rising water also puts historic, cultural and recreational sites at risk.

Flooding at Fort Caroline National Memorial, within the preserve, in September 2022 after Hurricane Ian. Photo: Steve Kidd, National Park Service.

Sea-level rise and tidal flooding

• Relative SLR: sea level is rising worldwide with climate change, but at different rates in different places, because of ocean circulation and density, land rising or sinking, and where and how much ice is lost from ice sheets and glaciers.
• Scenarios: a multiagency report set out five global scenarios — low, intermediate-low, intermediate, intermediate-high and high — depending on greenhouse gas emissions and ice loss. This study used their regional and local projections, with a median and a "likely" range (17th–83rd percentile).
• High tide flooding happens when spring tides — the highest tides, at full or new moon, when Earth, Moon and Sun line up — high winds or storms push water to extreme levels. NOAA sets minor, moderate and major thresholds for each location: minor floods can close roads, moderate ones do more damage, and major ones can destroy property and force evacuations.

Today, minor high tide floods usually happen only a few days a year on the southern Atlantic coast, and moderate and major ones less than once a year. Rising seas will make them much more frequent within a few decades: by 2100, under the intermediate-low scenario, minor flooding is projected more often than every other day — today's flood level could become the ordinary high tide. Even minor flooding is becoming serious, and many floods together can wear down infrastructure on low ground. Tidal flooding is a present-day effect of sea-level rise, and may signal what is coming.

The five sea-level rise scenarios for the preserve to 2100: each line is the median projection, the shading its likely range. Chart: U.S. Geological Survey.

What the maps show

Projected sea-level rise (from 1992, median and likely range):

Share of the preserve's non-water area likely inundated (probability above 0.66):

Where the preserve is likely to be inundated under the intermediate-low and intermediate-high scenarios in 2050 and 2100. Maps: U.S. Geological Survey.

High tide flooding thresholds, above mean higher high water:

Flooding probability at the minor, moderate and major high tide flooding thresholds. Maps: U.S. Geological Survey.

Using the maps

The maps can help managers judge current and future effects of rising water on habitats, historic and cultural resources and infrastructure, and support decisions under the resist-accept-direct (RAD) framework. The same approach can measure and map future habitat change, such as tidal saline wetlands moving inland. The data and methods are in a USGS data release (Thurman and others, 2024).

Sources

Based on "Projected sea-level rise and high tide flooding at Timucuan Ecological and Historic Preserve, Florida," U.S. Geological Survey, with the National Park Service, drawing on Sweet and others (2018, 2022), Thompson and others (2021) and Thurman and others (2024); a work of the United States government in the public domain. The maps, charts and photographs are reproduced from the fact sheet.