(Stacker) – Rising sea levels. Runoff from rapidly melting snow and ice. Rivers and streams overflowing their banks. As climate change continues to wreak havoc on the environmental norms humans widely take for granted, the frequency and severity of extreme weather has increased on a global scale.

Floods, the most common and fatal natural disasters in the U.S., continue to get more destructive. Catastrophic flooding events once thought to occur every 100 years could become annual happenings. And the nation’s floodplains are projected to grow by roughly 45% by the end of the century.

Because of the deterioration and fragility of historical buildings, as well as long-term degradation of the natural environment around these structures, historic sites are often at serious risk of flooding. 

Stacker identified historic buildings of national significance across the U.S. located in census tracts with very or relatively high risk of flooding, using data from Federal Emergency Management Agency’s National Risk Index and the National Register of Historic Places.

The National Park Service outlines six criteria for what makes a historic building on the registry nationally significant, a less rigorous designation than being considered a National Historic Landmark. FEMA calculated the risk of flooding for each census tract by combining geospatial and historic flood-event data from the National Flood Insurance Program and National Oceanic and Atmospheric Administration.

(Stacker is also publishing the raw data it merged to produce this story, available on GitHub and data.world.)

California by the numbers

California has 10 historically significant buildings with risk of river flooding, including:
— Charles M. Pratt House, Ojai (relatively high risk)
— Oak Grove Butterfield Stage Station, Oak Grove (relatively high risk)
— Petaluma Adobe, Petaluma (relatively high risk)

Petaluma Adobe was the residence of Rancho Petaluma, a massive agricultural empire run by the powerful General Mariano Guadalupe Vallejo from 1834-46, before the cession of California from Mexico to the U.S. in 1848. A major flood event at Petaluma Adobe in 2005 revealed a hidden deposit of Mexican Republic-era materials, some associated with the smallpox epidemic of 1837-39. Some of the more valuable items recovered suggest the previous owners were of high status.

California ranks 15th overall for the number of historic sites threatened by flooding.

States with the most historic sites at risk of flooding

1. Florida: 32 historically significant buildings with risk of flooding
2. New York: 28 historically significant buildings with risk of flooding
3. Arizona: 24 historically significant buildings with risk of flooding
4. Pennsylvania: 22 historically significant buildings with risk of flooding
5. Texas: 21 historically significant buildings with risk of flooding