Two studies, published today in the journal "Environmental Research Letters," provide evidence that sea levels are rising, creating higher and higher floods that will inundate much of the low-lying coastal United States.
A U.S. Air Force Reserve crew rescues a family in the coastal Texas town of Nederland trapped on their roof by flood waters from Hurricane Ike, September 13, 2008. (Photo by Tech. Sgt. Paul Flipse courtesy U.S. Air Force)
"Sea level rise makes every single coastal storm flood higher," said Strauss. "With so many communities concentrated on U.S. coasts, the odds for major damage get bigger every year."
The first study, by researchers at Climate Central and the University of Arizona, finds that around 32,000 square kilometers (12,355 square miles) of U.S. land lies within one vertical meter of the high tide line.
This area encompasses about 2.1 million housing units where 3.9 million people live.
For this study, the researchers created a new model to identify the areas of the U.S. mainland that are at risk of flooding. With a predicted sea level rise of one meter (39 inches) or more by the end of the century, this study suggests that the U.S. government's currently designated flood zones should not be considered stable.
This study demonstrates that coastal dwellings on every coast are exposed to this risk. At the state level, areas surrounding the Gulf of Mexico appear to be the most vulnerable. In terms of population, Florida is the most vulnerable, followed by Louisiana, California, New York and New Jersey.
The Los Angeles metropolitan area is of great concern, the researchers warn, citing previous studies suggesting that flooding may reach rare heights more swiftly in southern California than in any other U.S. mainland area.
The second study examined the effect of heavy storms on past water levels at 55 stations across the United States and combined these with estimates of future global sea level rises to predict the frequency and extent of future flooding.
High seas and winds battered and flooded a coastal area of Nags Head, North Carolina (Photo by Dave Gatley courtesy FEMA)
The second study corroborates evidence of the risk shown in the University of Arizona study. It shows that a majority of the 55 locations studied, will see a "substantially higher frequency" of storm-driven high water levels by the middle of the century - water levels that have previously been encountered only once in a century.
Global warming has raised global sea level about eight inches since 1880, and the rate of rise is accelerating, said Climate Central in a statement today. Analysts at the nonprofit research and journalism organization based in Princeton, New Jersey find the odds of "century" or worse floods occurring by 2030 are "on track to double or more" over widespread areas of the United States.
Titled "Surging Seas," a Climate Central report released today based on the two just-published studies is the first to analyze how sea level rise caused by global warming is compounding the risk from storm surges throughout the coastal contiguous United States.
Condos in Melbourne Beach on Florida's east coast at risk of sea level rise (Photo by Ty Harrington courtesy FEMA)
The Surging Seas website includes a searchable, interactive online map that zooms down to neighborhood level, and shows risk zones and statistics for 3,000 coastal towns, cities, counties and states affected up to 10 feet above the high tide line.
Many locations are projected to experience such high flooding every decade or even more often as sea levels rise due to the melting of glaciers and the expansion of water as it warms.
By 2030, many locations are likely to see storm surges combining with sea level rise to raise waters at least four feet above the local high-tide line. Nearly five million U.S. residents live in 2.6 million homes on land below the four-foot level.
More than six million people live on land below five feet; by 2050, the study projects that widespread areas will experience coastal floods exceeding this higher five-foot level.
Flooding to four feet is projected to inundate some three million acres of roads, bridges, commercial buildings, military bases, agricultural lands, toxic waste dumps, schools and hospitals, causing many billions of dollars worth of damage over the coming decades.
In its most recent report, the Intergovernmental Panel on Climate Change, the international scientific body charged with assessing climate change, estimates the seas will rise up to two meters (6.6 feet) by the end of this century.