Every year, storms from the tropics flood the West Coast, and a new study estimated the weather creates annual damage worth $1 billion.
The Scripps Institution of Oceanography released an economic study Wednesday outlining how branching storms from the equator, known as atmospheric rivers, impact the West Coast.
Over the past 40 years, flooding has caused nearly $51 billion in damages to western states, according to the University of California, San Diego institute.
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And a large majority – 84 percent – of the damage was a result of these special weather patterns. Specifically, in Northern California and Oregon, that number jumped to more than 99 percent.
Tropical moisture hovers in the air around the equator and will occasionally drift north or south of the Earth’s center in a “finger of moisture” like a flowing river, according to NBC 7 Meteorologist Dagmar Midcap. This is known as an atmospheric river.
“(A) particular atmospheric river that often moves up into Central California originates near the Hawaiian Island chain,” Midcap said. This is known as the Pineapple Express, though not all atmospheric rivers that hit San Diego originate from Hawaii.
The atmospheric rivers can carry more than twice the volume of the Amazon River through the sky, according to the Scripps Institution of Oceanography.
“A small number of extreme ARs cause most of the flood damages in the West,” said Scripps postdoctoral researcher and study leader Tom Corringham. “And even modest increases in intensity could significantly increase their impacts.”
In 2018, Scripps researchers created a scale to measure the force of the atmospheric rivers, one being a mostly beneficial storm to five being a mostly hazardous storm.
Researcher F. Martin Ralph and his team outlined that for every increase in the scale, the flood damage is multiplied by ten.
These storms have catastrophic potential, as the UCSD report noted that 10 atmospheric rivers caused $23 billion in damages – nearly half of all flooding damage to the region in four decades.
On average, flood damage totals $1.1 billion each year throughout the West.
The study showed how a few atmospheric rivers can determine whether a region will be in drought or flood years.
“This is a reminder that weather and climate matter,” Corringham said. “Every step we take now to stabilize the global climate system stands to reduce future adverse impacts on our economy.”
Researchers expect the atmospheric rivers to intensify as global warming trends increase, according to the study.
In the end, the report encouraged restoring natural floodplains and discouraged new development in flood-prone areas.
The study was funded by the National Oceanic and Atmospheric Administration through the California Nevada Climate Applications Program, as well as the federal Bureau of Reclamation and the University of California Office of the President.
Researchers from the Scripps Institution of Oceanography and the U.S. Army Corps of Engineers collaborated on the report.