The rising sea level is bad for business. Already today. Specifically, this shows, for example, for 16 small traders on the shores of the US city of Annapolis. When seawater spilled over the coastal fortifications several times in 2017, the shop owner, café owners and innkeepers cost between $ 86,000 and $ 172,000 (equivalent to between € 76,000 and € 152,000) - just because customers stayed away.

This is the conclusion reached by scientists around Miyuki Hino and Christopher Field of Stanford University in a recent study in the journal Science Advances, which they presented at the AAAS Science Conference in Washington.

"There were 63 tides in Annapolis in 2017," says Field. Such floods only last for a short time and usually cause little damage. At high tide, water overflows and runs on sidewalks, parking lots and in streets. With the ebb, it retreats back. In contrast to the effects of major storms, the economic consequences are hardly known.

In Germany, 3.2 million people live in risk areas

"As a single event, tidal floods are pretty unspectacular," says Field. "But considering that they occur in many cities and become more common as the sea level rises, one should not underestimate their impact on the local economy." Annapolis is just one example, in fact many other cities are affected.

In 2017, the US ocean agency NOAA evaluated the number of tidal floods in 27 locations in the US. While in the late fifties there was an average of tidal floods only for two 2.1 days, the figure for 2006-2010 was 11.8. Researchers estimate that in 2035 there will be more than 26 such floods in just under 170 US coastal cities. What are the losses for businesses outside Annapolis, still needs to be explored.

"Often we see global warming and sea-level rise as an abstract thing happening on a global scale," Hino says. "Tidal floods are an example of how climate change impacts our everyday lives - even if it's just an additional ruptured reservation in the restaurant."

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Sea level rise in Germany threatening Germany's coasts

Experts in Germany are also worried about rising sea levels. But it's all about storm surges. In flood-prone areas on the North Sea and Baltic Sea coast, about 3.2 million people live according to a drafting by the German Government's Research Service. Huge new dike shells prevent the water from returning to the land.

The floods drove 3000 visitors

The US city of Annapolis provided the best conditions for researchers to investigate the specific effects of tidal floods. The capital of the state of Maryland has a good 39,000 inhabitants and is located in the Chesapeake Bay on the Atlantic. Immediately on the waterfront are historic buildings with small shops and a paid parking (see map). The number of tidal floods has increased dramatically in recent decades - from about four events per year in the sixties to 63 in 2017.

To find out how the many floods in 2017 affected the number of visitors, the researchers evaluated the parking meters in the parking lot. "That way we could see exactly how many hours were up at the time," explains Hino. When exactly water was in the parking lot, told them a security camera. The researchers compared the number of visitors on days with and without flood and calculated the difference.

"We saw how many visitors were in the parking lot on a normal sunny Tuesday afternoon in October, and how many were flooded under the same conditions," Hino said.

According to them, the shops lost 3000 visitors in the flood hours. The researchers did not find any evidence that customers made up their shopping at low tide. The value is equivalent to a decline in visitors of about two percent - and the losses could be even greater in the coming years:

  • If the water level rises another seven centimeters, four percent of the visitors could be lost, the scientists report.
  • At a good 30 centimeters, they expect almost a quarter fewer visitors.

For comparison, experts in the US estimate that by 2050, sea levels will rise by about 15 to 36 centimeters from 2000 levels. They scenarios of researchers thus appear quite realistic. Annapolis is considering protecting its stores from flooding with pumps and canals.