The moon’s gravitational pull, rising sea levels and climate change can bring catastrophic coastal floods in a decade or two, a recent study has predicted.

A combination of these three factors will exacerbate coastal flooding across the world, NASA Administrator Bill Nelson recently warned.

Nelson said the study, led by NASA Sea Level Change Team from the University of Hawaii, has predicted an increase in high tide flooding (HTF) in multiple coastal regions of the United States in the mid-2030s, resulting in a catastrophically wet decade at these places.

HTF could happen more frequently on many coasts like the Atlantic, already affected by regular flooding. The study said that rising sea levels due to climate change and the moon’s wobble could worsen the flooding, often called nuisance flooding.

The moon

The moon's orbit is due for its regular "wobble". According to NASA, this is a natural phenomenon, and the moon’s last wobble was recorded as far back as 1728. It is to be noted that half of the moon's 18.6-year cycle creates lower high tides and higher low tides; while the other creates higher high tides and even lower low tides.

NASA said global sea-level rise (SLR) will likely push the high tides higher. Ben Hamlington, NASA Sea Level Change Team leader, said that since the seawaters will be higher, this moon cycle can have a much more dramatic effect.

"We're getting closer to the flooding thresholds. The same variability in the past that didn't cause flooding is now going to do so," says Hamlington.

High tides

High tides have already been exceeding the known flooding thresholds around the US. In 2019, the National Oceanic and Atmospheric Administration reported continued record-setting high tide, or sunny day, flooding.

But the study predicts that floods can start occurring in "clusters" that last a month or more, depending on the positions of the sun, moon and Earth.

"Low-lying areas are increasingly at risk and suffering due to the flooding. It will only get worse," warned Nelson.

The preps

Hamlington said that cities and urban planners along the coasts already familiar with HTF have been acting to prevent future damage. But the study said that higher tides and longer floods are coming faster than anticipated.

"We are going to see these big dramatic shifts in the next decade or two," NPR quoted him as saying.

First Published:Jul 15, 2021 3:14 PM IST