"Nuisance" floods may cost U.S. cities as much as major hurricane disasters - scientists

by JD Capelouto | @jdcapelouto | Thomson Reuters Foundation
Tuesday, 7 March 2017 16:00 GMT

A home is seen submerged in water after an overflowed Coyote Creek flooded nearby neighborhoods and prompted an evacuation in San Jose, California, U.S., February 22, 2017. REUTERS/Stephen Lam

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As climate change causes sea levels to rise, escalating costs from minor floods are expected to hit U.S. coastal cities

By JD Capelouto

LONDON, March 7 (Thomson Reuters Foundation) - Minor floods caused by rising sea levels may end up costing U.S. coastal communities as much money and resources as major hurricane disasters, U.S. scientists said.

As climate change causes sea levels to rise, such "nuisance flooding" is expected to become more frequent and hit cities like Washington, D.C., San Francisco, Boston and Miami where it hurts — the wallet, researchers said.

Over the last 20 years, Washington has endured more than 94 hours a year of nuisance flooding. By 2050, the capital could see as many as 700 hours of flooding a year, the scientists estimated in a study published in American Geophysical Union journal Earth's Future.

"Since these events are not extreme, they don't get a lot of attention," said Amir AghaKouchak, professor of civil and environmental engineering at the University of California, Irvine (UCI), and co-author of the study.

Nuisance flooding is defined by the National Ocean Service as "flooding that leads to public inconveniences such as road closures", but rarely causes death or injury.

The floods can overwhelm storm drains, and slowly degenerate infrastructure and strain city resources.

Roads and sidewalks were not built to be under saltwater for hours on end, and cities usually have to close roads and send in trucks to clean them up, the scientists said.

"They definitely can't withstand this," said lead author Hamed Moftakhari, also of UCI. And the damage leads to "long, drawn-out costs", he added.

In Boston specifically, "king tides" overwhelm walkways and roads several times a year. The east coast city is predicted to see up to 100 hours of such nuisance flooding a year by 2030, the UCI scientists said.

Residents have already noticed the semi-frequent inconvenience, according to Mia Goldwasser, Boston's climate preparedness programme manager.

"There's always people sending pictures to the city saying, 'Look at all the flooding happening with very little rain'," she told the Thomson Reuters Foundation in a telephone interview this week.

The city has already noted several waterfront hotspots where "it's going to be worse [in the future] if there's already flooding".

The flooding has raised awareness among the general public to the everyday realities of climate change, she said.

"It's an inconvenience to people when they're walking and driving and biking, moving around their neighbourhood," Goldwasser said.

CHANGING TIMES, RISING TIDES

The scientists are using the data as a "call to action" for coastal cities to examine the issue and decide on the best ways to respond to rising sea levels.

"We believe that if you have information on the type of hazard, the potential cost, then you can plan," said AghaKouchak.

Boston has begun to come up with ideas to mitigate the effects of rising seas on infrastructure, which include flood proofing properties and potentially building a massive sea wall.

Some roads and buildings may become corroded by nuisance floods, others could end up completely underwater, Goldwasser said.

"There's still a lot that we don't know, that we're trying to figure out," she said. "What are the most effective solutions ... How do we actually implement them?"

And as for the total costs of the floods over the next few decades? Goldwasser said that's still to be determined, though they "expect them to be pretty significant". (Reporting by JD Capelouto; Editing by Alex Whiting. (Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, climate change, resilience, women's rights, trafficking and property rights. Visit http://news.trust.org/climate)))