Sea Level Rise Threats in the US, California, and Florida

Sea Level Rise Threats to Coastal Property In the US, California, and Florida by Value

We summarize the sea level rise threats to coastal property including the number of properties at risk, the property value at risk, the property tax at risk, and the population at risk.

We concentrate on the US overall, California, Congressional Districts in California, and, the most valuable and at risk state, and already flooding, Florida.

The data come from two comprehensive studies from the Union of Concerned Scientists (UCS), using housing value data from Zillow.

The studies use three sea level rise scenarios, which by 2100 attain:  High, 6.5 feet (and 2 feet by 2045); Medium or Intermediate, 4 feet; and Low, 1.6 feet.  Low means that we keep the total temperature increase since pre-industrial times below 2.0 ºC, which is the eventual Paris agreements goal, and highly unlikely to be achieved (we’re already at 1.0 ºC).  The conservative IPCC estimates are at most 3 feet or one meter.  The 6.2 foot scenario is with Greenland and/or Antarctic land ice melting, and is possible, but not scientifically predicted with any certainty.  However, if you are concerned with just basic flooding, not chronic flooding, you have to add in extra high tides, or high tides with several feet of storm surges, which will likely increase in strength, overcoming the 100 year storm rarity.  Since a single flood can set you back a massive rebuilding, the High Scenario has relevance.  You can also look at the 2045 High Scenario 2 foot rise as the minimum of the conservative IPCC report at 2100.

The data also include projections for 2030, 2035, 2045, 2060, 2080, and 2100.  We will usually only take 2100.

Using the High scenario, the UCS summary is by 2045, 300,000 coastal homes with a current market value of $118 billion are at risk of chronic, or 26 days a year, flooding.  14,000 coastal commercial properties worth $19 billion are also at risk.

By 2100, the total property at risk is more than $1 trillion, including 2.4 million homes.

States with the most homes at risk by 2100 are Florida at 1,000,000 (10%),  New Jersey at 250,000, and New York at 143,000.  California only comes in at 109,000 homes.

California Congressional Districts on the Coast with the Most Value at Risk:

CA 48, our local one around Newport Beach, in the High Scenario has by 2045:  3,700 homes at risk worth $4 billion, house 9,000 people, and contribute $43 million in property taxes.  By 2100, about 12,300 homes are at risk worth $14 billion today.  If the Low Scenario can be achieved, 72% of these would be spared.

CA 18, south of San Francisco, in the High Scenario has by 2045:  2,400 homes at risk worth $2.5 billion, house 5,700, and contribute $28 million in property taxes.

CA 2, including San Francisco, in the High Scenario has by 2045, 4,600 homes at risk worth $2.7 billion, hose 10,000 people, and contribute $41 million in property taxes.

From US risk maps, we see that Gulf of Mexico coasts, Florida coasts, and East US coasts are most at risk from sea level rise.  On the West coast, these are only matched by the San Francisco and Seattle areas.

US Congressional Districts with high value at Risk in 2045 under the High Scenario, besides the California ones above, include:  New Jersey 2, $19 billion; South Carolina 1, $6.8 billion; Florida 26, $5.5 billion; Maryland 1, $4.0 billion; Florida 16, $2.5 billion; Georgia 1, $2.2 billion; Lousiana 1, $1.9 billion, and Lousiana 6, $1.05 billion.

California Homes at Risk In Different Scenarios and Dates:

Under the High Scenario, CA homes at risk are for:  today 7,000; 2030 13,600; 2045 20,500; 2060 30,200; 2080 76,300; and 2100 100,000.

Under the Intermediate Scenario, CA homes at risk are for:  2035 12,500; 2060 19,800; 2080 29,000; and 2100 68,600.

Under the Low Scenario, CA homes at risk are for:  2060 12,600; and 2100 19,200.

California Market Value at Risk at 2100:  High Scenario $75 billion; Intermediate Scenario $48 billion; and Low Scenario $14 billion.

California Population at Risk at 2100:  High 273,000; Intermediate 171,000; and Low 47,000.

US Homes at Risk at 2100:  High 2.4 million; Intermediate 1.2 million; and Low 0.34 million.

US Value at Risk at 2100:  High $910 billion; Intermediate $500 billion; and Low $130 billion.

US Population at Risk at 2100:  High 4.7 million; Intermediate 2.2 million; and Low 0.6 million.

Florida Homes at Risk under the High Scenario at dates:  Today 12,300; 2030 21,000; 2045 64,000; 2060 172,000; 2080 485,000; and 2100 1.03 million.

Florida Homes at Risk at 2100:  High 1.0 million;  Intermediate 0.40 million; and Low 0.075 million.

Florida Value at Risk at 2100:  High $350 billion; Intermediate $165 billion; and Low $31 billion.

Florida Population at Risk at 2100:  High 2.1 million; Intermediate 690,000; and Low 120,000.

For High, Intermediate, and Low Scenarios, the number of homes at risk in 2100, Florida is 42%, 33%, and 22% of the US, respectively.  California is 4.1%, 5.7%, and 3.2%, respectively, for High, Intermediate, and Low Scenarios.

In general, half the damage is achieved by seeking the Intermediate Scenario rather than the High Scenario.  A quarter of the damage is achieved by the seeking the Low Scenario rather than the Intermediate Scenario. 

About Dennis SILVERMAN

I am a retired Professor of Physics and Astronomy at U C Irvine. For a decade I have been active in learning about energy and the environment, and in lecturing and attending classes at the Osher Lifelong Learning Institute (OLLI) at UC Irvine.
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