July 26, 2019
Military Installations and Sea-Level Rise
The Department of Defense (DOD) manages more than
1,700 military installations in worldwide coastal areas that
may be affected by sea-level rise. These installations
support DOD readiness and operations including naval
vessel embarkation and disembarkation, amphibious
training, and special operations forces training. Military
installations on and near the coast are at risk for high-tide
and storm surge flooding amplified by sea-level rise.
Congress may choose to assume a role in preparing military
installations for sea-level rise based on its authority in fiscal
and national security matters.
Sea-Level Rise and Climate Change
Global climate observations from the National Oceanic and
Atmospheric Administration (NOAA) show trends of
increased surface, air, and ocean temperatures that correlate
with sea-level rise. The U.S. Global Change Research
Program (USGCRP) reports that global mean sea level
(GMSL) has risen by approximately 7-8 inches since 1900;
further, GMSL has risen 3 inches since 1993 (see CRS
Report R43229, Climate Change Science: Key Points, by
Jane A. Leggett).
NOAA identifies the two major causes of GMSL rise as
thermal expansion (water expanding from rising ocean
temperature) and melting land ice (ice sheets and glaciers)
adding water to ocean basins. Factors such as land
rebounding, sediment compaction, oil and gas extraction,
and land management influence relative sea level (RSL),
the sea level relative to the land surface from which it is
measured (for more information, see CRS Report R44632,
Sea-Level Rise and U.S. Coasts: Science and Policy
Considerations, by Peter Folger and Nicole T. Carter).
Figure 1. Relative Sea-Level Change Trends & Military
Installations in West Coast Congressional Districts, 2017
Source: NOAA, Tides & Currents, “U.S. Sea Level Trend Map”; U.S.
Census Bureau; Homeland Infrastructure Foundation-Level Data.
Notes: Colored dots are monitoring stations; CD = Congressional
District with coastline; mm/yr = millimeters per year.
Figure 2. Relative Sea-Level Change Trends & Military
Installations in East Coast Congressional Districts, 2017
Source: NOAA, Tides & Currents, “U.S. Sea Level Trend Map”; U.S.
Census Bureau; Homeland Infrastructure Foundation-Level Data.
Notes: Colored dots are monitoring stations; CD = Congressional
District with coastline; mm/yr = millimeters per year.
RSL trends vary across the U.S. coastline (see Figure 1 and
Figure 2). For example, in 2017, RSL was rising at a rate
of 9-12 millimeters per year along Louisiana’s Mississippi
River Delta where parts of the land surface was sinking
(Figure 2), while RSL was dropping along portions of the
Pacific Northwest coastline and near southern Alaska
(Figure 1). With few exceptions, RSL is rising along the
coastlines of the contiguous United States; according to
USGCRP, both GMSL and RSL levels are expected to
continue to rise for the foreseeable future.
Impacts to Military Installations
Military installations differ in terms of their existing
infrastructure and potential vulnerabilities. A number of
coastal military installations already routinely experience
high-tide flooding, and storm surge from recent hurricanes
has exacerbated flooding, disrupted operations and caused
extensive damage to infrastructure. Likewise, infrastructure
outside of military installations, (e.g., mission critical
access roads) can be impacted by sea-level rise, further
impeding military operations.
A study led by DOD’s Strategic Environmental Research
and Development Program (SERDP) observed that sea-
level rise threatens the sustainability of coastal installations
through intensified storm surge, increased flood frequency,
and saltwater intrusion into the groundwater aquifer (see
SERDP study RC-1701). SERDP study RC-2334 found that
U.S. military installations on low-lying atolls in the Pacific
Ocean will be negatively impacted when “mean sea level is
0.4 meters higher…the amount of sea water flooded onto
the island will be of sufficient volume to make the
groundwater non-potable year-round.” In the 2014 Climate
Change Adaptation Roadmap, DOD identified the Hampton
Roads, VA region, which houses the largest concentration
of military sites in the world, as vulnerable to projected
