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They’re back. Those big tides we saw for several months last fall are returning this week. Astronomical high tides are nothing new; they have been occurring for millennia. Recently, such tides have been branded as “king tides” because they are some of the biggest tides of the year.

As the moon orbits the Earth, its effect on our tides varies daily, weekly, and monthly. Every month of the year has a maximum tide cycle, but during some months tides rise higher than others.

The tides will fluctuate 10 feet from low to high this week. (NOAA)
The tides will fluctuate 10 feet from low to high this week. (NOAA) NOAA

This week the highest of the high tides occurs Thursday and Friday, but Tuesday and Wednesday’s tides are also very large. This, combined with a nor’easter for the same time period, will bring an increased chance of shore road flooding.

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During the upcoming nor’easter the high tides Tuesday and Wednesday will produce some coastal flooding.
During the upcoming nor’easter the high tides Tuesday and Wednesday will produce some coastal flooding.US Harbors

This isn’t going to be a major flooding event, but I do expect some road closures. Minor beach erosion is also expected as the continued easterly fetch of wind piles up water against the shoreline Tuesday and Wednesday.

A slow-moving coastal storm will bring rain and wind to the region early Tuesday through Wednesday. (Tropical Tidbits)

King tides are useful for another purpose. These highest of the high tides give us a window into the future when climate predictions estimate our tides will be 1 to 2 feet higher by the beginning of the next century. Twelve-foot tides could become routine with the equivalent of a 14-foot tide as the new king tide by 2100 and beyond.

A king tide cycle and a storm is what urban planners and those building the infrastructure of the future need to worry about. Imagine a winter coastal storm and high astronomical high tides. If the storm remained stalled for multiple days and you had big tides, coastal flooding would reach catastrophic levels. This is precisely what happened in the Blizzard of 1978, and there’s no reason to think it’s not going to happen again at some point in the future.

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Bill Brett/Globe Staff/File

You can follow Dave Epstein on Twitter @growingwisdom