Sea-Level Rise and High-Tide Flooding at Big Cypress National Preserve

National parks and preserves in the Park Service's South Atlantic–Gulf Region hold valuable coastal habitats, such as tidal wetlands and mangrove forests, and irreplaceable historic buildings and archeological sites on low ground. Accelerating sea-level rise and more frequent high-tide flooding threaten both. In a project funded by the Natural Resources Preservation Program from 2021 to 2023, the U.S. Geological Survey (USGS) and the National Park Service estimated how likely parts of Big Cypress National Preserve and several other parks are to be flooded under different scenarios. The resulting maps can help assess habitat change and how infrastructure and cultural resources may be exposed to future flooding.

Big Cypress National Preserve. Photograph by National Park Service staff.

The preserve

Big Cypress lies north of the Everglades on the western side of the Florida peninsula and covers 2,934.52 square kilometers of land, not counting water and aquatic bed wetlands. Its freshwater wetlands are essential to the health of the Everglades and the rich estuaries along Florida's southwest coast. Its coastal habitats are at risk unless they can keep pace by building up vertically or move to higher ground, and rising seas also put historic, cultural and recreational sites at risk.

Location of Big Cypress National Preserve in Florida. USGS figure.

Sea-level rise scenarios

Global climate change is driving sea-level rise that is affecting low-lying coasts worldwide. The rate varies from place to place with ocean circulation and density, the rise or sinking of the land, and where and how much ice melts from ice sheets and glaciers; the local rate is called relative sea-level rise. A multiagency report produced five global scenarios, from low to high, depending on greenhouse gas emissions and ice loss. This study used regional and local projections tied to those scenarios, each with a median value and a "likely" range (17th to 83rd percentile).

Relative sea-level rise scenarios for Big Cypress, relative to 1992 (after Sweet and others, 2022). USGS figure.

Measured from a 1992 base year, the projections for Big Cypress are:

And the share of the preserve's non-water area likely to be inundated (probability above 0.66):

Sea-level rise inundation probabilities for Big Cypress: intermediate-low (A, 2050; B, 2100) and intermediate-high (C, 2050; D, 2100). USGS figure.

High-tide flooding

High-tide flooding happens when spring tides (the highest tides, at full or new moon when the Earth, Moon and Sun line up), strong winds or storms push water unusually high. NOAA sets local thresholds: minor flooding disrupts trails and other infrastructure, moderate flooding causes more disruption and possible damage, and major flooding can destroy property and force evacuations.

Today, along the eastern Gulf of Mexico coast, minor high-tide floods typically happen only a few days a year, and moderate and major ones less than once a year. Sea-level rise makes them worse, and they are expected to become much more frequent within decades. By 2100, under the intermediate-low scenario, minor high-tide flooding is projected to happen more than every other day, meaning today's flood level could become the future's ordinary high tide. Floods once dismissed as nuisances are becoming serious, and their cumulative damage to low-lying infrastructure can be large.

At Big Cypress, the thresholds are 54 cm (plus or minus 19 cm) above mean higher high water for minor flooding, 83 cm (±25 cm) for moderate and 121 cm (±39 cm) for major. Under all three, most of the preserve's land was unlikely to be inundated, but the area likely to flood grew from about 13% at the minor threshold to about 22% at the major one.

Flooding at the maintenance complex behind Big Cypress headquarters on September 29, 2022, the day after Hurricane Ian made landfall. Photograph by National Park Service staff.

High-tide flooding inundation probabilities for Big Cypress at the A, minor, B, moderate, and C, major thresholds. USGS figure.

Using the maps

The maps can help managers assess 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 for managing change. The same approach can also show how habitats may shift, such as tidal saltwater wetlands migrating inland.

Sources

• U.S. Geological Survey, "Projected sea-level rise and high tide flooding at Big Cypress National Preserve, Florida," Fact Sheet 2024–3022. https://pubs.usgs.gov/publication/fs20243022
• The fact sheet draws on Sweet and others (2018, 2022) for sea-level and flooding scenarios, Thompson and others (2021) on flood frequency, Schuurman and others (2020) on the RAD framework, and a USGS data release by Thurman and others (2024) with the maps and methods. Its wording follows Thurman and others (2024a).
• Figures and photographs recovered from the fact sheet PDF.