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Climate Change: The Fiscal Risks Facing The Federal Government/Federal Facility Flood Risk

5. FEDERAL FACILITY FLOOD RISK

Federal Facility Flood Risk.png

Hundreds of billions of dollars of Federal assets nationwide face flood risk today—and tens of billions of dollars of coastal assets could be inundated or severely affected by sea level rise by the end of this century. Depicted above, from left to right, is Naval Air Station Key West at typical high tide today, with 2 feet of sea level rise, and with 4 feet of sea level rise. Green represents low-lying but hydrologically unconnected areas. Blue represents areas inundated at high tide. Source: NOAA Sea Level Rise Viewer (https://coast.noaa.gov/slr/).


Climate Change and Flood RiskEdit

Just as American homeowners and businesses face growing flood risks due to climate change, so does the Federal Government.[1] The NCA found that climate change may intensify flooding in many U.S. regions, even where total precipitation is projected to decline. Increasingly heavy downpours can cause flash and urban flooding and, along with more rapid spring snowmelt, can exacerbate river flooding. Climate-related sea level rise from thermal expansion of ocean water and melting of glaciers and ice sheets can cause coastal flooding and compound damages from storm surges (Melillo et al., 2014).

A common measure of flood risk for a given structure is whether it would be inundated by flood hazards that have at least a one percent annual chance of occurring based on historical hydrological patterns— the so-called “100-year floodplain.”[2] With climate change, the current 100-year floodplain is expected to widen, while structures in the current 100-year floodplain are generally expected to see more frequent and severe flooding (AECOM, 2013). While FEMA has mapped the 100-year floodplain in the areas of the United States with the majority of the population, the projected 100-year floodplain area as influenced by climate change is not readily available.

However, changes in risk are more easily identified in coastal areas, where sea level rise projections have been mapped. The 2014 NCA considered 1-4 feet of additional sea level rise as the likely range by the end of the century, depending on future emissions and other factors (note that global sea level has risen by about 8 inches since reliable record keeping began in 1880, and the rate of sea level rise since 1992 has been roughly twice the rate observed over the last century). However, the NCA painted 8 inches and 6.6 feet as bounds for risk-averse planning. The NCA also noted that sea level rise will not stop in 2100 and may continue for many centuries even if global warming is stabilized (Melillo et al., 2014). Since the 2014 NCA, more recent findings about the rate of melting in Antarctica suggest the high end of the range may be closer to 8 feet (DeConto and Pollard, 2016).

The National Oceanic and Atmospheric Administration (NOAA) has mapped projected sea level rise in the continental U.S. and Hawaii, delineating the area that would be inundated under the typical high tide under different degrees of future sea level rise. In addition to areas inundated at typical high tide, sea level rise will affect a broader area by increasing the risk of storm surge and “nuisance flooding” with strong tides. For example, the NCA documented how even a 1 foot sea level rise above mean high tide in 2050 could cause the level of flooding associated with today’s 100-year storm to occur instead as often as once a decade or even annually (Melillo et al., 2014).

Risk AssessmentEdit

The Federal Government has not yet created a comprehensive dataset of location data for all Federal buildings and structures to allow them to be easily mapped. Due to this fact, the Federal Real Property Profile (FRPP) data were used to map Federal assets. As the FRPP was not designed to provide robust mapping capability, a full and complete assessment of Federal property flood risk is not feasible with the FRPP. FRPP includes precise location data for about one-third of federally owned buildings and structures located within the United States. Within this subset of the inventory, OMB identified 18,000 individual buildings and structures with a total replacement cost of $83 billion located in the current 100-year floodplain, based on FEMA floodplain maps—roughly 8 percent of the subset of records and 14 percent of the subset replacement value. Tens of thousands of additional assets, with a total replacement cost of $25 billion, were identified in the current 500-year floodplain.

The structures not examined have a total replacement cost of $1.0 trillion. Generally, assets without precise location data are national security facilities, as well as several types of non-building assets such as transportation and communications infrastructure. The portion of assets reviewed generally includes non-defense facilities like office buildings, warehouses, housing, laboratories, and hospitals.

The extent of future changes in flood risk has not been estimated across the full Federal inventory. However, OMB used NOAA sea level rise maps to assess inundation risk at a sample of coastal facilities—including facilities that were excluded from the floodplain assessment due to lack of precise location data. Of 57,000 inventory records reviewed in coastal areas, OMB identified 12,000 individual Federal buildings and structures, with a replacement cost of $62 billion, that would be inundated or severely affected[3] by the average high tide under a six foot sea level rise scenario. The majority of these assets are associated with the Department of Defense. A significant portion of these facilities appears to be located outside of the current 100-year floodplain, reinforcing the expectation that sea level rise will appreciably expand the number and value of Federal facilities facing flood risk in the coming decades.

OMB has not estimated the likely costs associated with this liability over the coming decades.[4] Replacement cost is an imperfect indicator of the rough scale of fiscal risk. Severe flooding or the promise of recurring inundation could require outright abandonment and/or replacement. In many cases, however, an individual flood event or the presence of flood risk may prompt less costly investments in protective infrastructure and repairs. The Federal Flood Risk Management Standard requires Federal agencies to consider current and future risk when rebuilding structures that have been damaged in a floodplain. Some protective investments may require one-time expenditures; others may occur and even increase over time as flood risk intensifies. Nonetheless, such investments for any given asset could be significantly smaller than the asset’s total replacement cost. For more information on the assessment, see the Technical Supplement accompanying this report.

Key Limitations and UncertaintiesEdit

The Federal Government remains in the early stages of identifying the full extent of flood risk facing Federal facilities under current and future conditions largely due to persistent data limitations.

First, the Federal Government lacks projected nationwide floodplain maps that reflect expected changes due to climate change. A 2013 study conducted for FEMA demonstrated the scale of climate impacts on flood risk, finding that by 2100 the typical 1 percent annual chance floodplain area would grow by 40-45 percent largely due to climate change (AECOM, 2013). However, FEMA’s maps are used to implement the National Flood Insurance Program and to provide communities with accurate flood hazard information, and therefore reflect existing flood risk. Without future projections, the full extent of the impact of climate change on flood risk for Federal facilities is not clear.

Second, detailed damage modeling has not been conducted on the Federal inventory to determine actual expected costs due to flooding. This type of assessment is conducted routinely by insurance companies in the private sector and would provide a clearer picture of Federal fiscal risk exposure than replacement cost. An assessment was also conducted for FEMA’s National Flood Insurance Program in 2013, finding that the total number of policies would increase by 80-100 percent by 2100 in part due to climate change, and that the average loss cost per policy would increase by 50-90 percent (AECOM, 2013). In combination with good analytics on current and future flood risk, damage modeling on Federal property would enable better planning for investments and divestments across the Federal inventory.

Third, the Federal Government has not yet created a comprehensive dataset that would enable precise spatial analysis of the entire Federal property inventory. Due to national security concerns, the FRPP does not include geographic coordinates for a broad set of defense and homeland security facilities. Similarly, the FRPP includes several types of non-building assets such as transportation and communications infrastructure for which geographic coordinates are not reported and street addresses are unreliable for the purposes of accurately determining flood risk.

In addition to these data limitations, risk assessments in this area are also affected by scientific uncertainty. In particular, local flood impacts from climate change can be difficult to project due to the challenges of downscaling global change models to the local level. In addition, while there is high confidence that sea levels have already risen and will continue to rise over this century and beyond, the future rate of sea level rise remains difficult to predict.


  1. The Federal Government owns more than 775,000 individual buildings and structures with a total estimated replacement cost of nearly $1.9 trillion.
  2. The 100-year floodplain is the area that will be inundated by the flood event having a 1 percent chance of being equaled or exceeded in any given year.
  3. For example, a building was considered “severely affected”—even if it would not be inundated itself—if its major access roads or ports would be inundated, or if major facilities on a shared campus would be inundated.
  4. Note that a portion of these costs associated with vulnerable Federal coastal assets is implicitly included in the coastal storm disaster relief estimates; however, those results do not capture any costs for facilities on the west coast or in Hawaii, or non-hurricane costs associated with sea level rise for assets on the east and gulf coasts.