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 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 Assessment
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 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.