King tides return to Puget Sound, but unlikely to bring much flooding

The king tides are back along Washington’s shoreline this week and should peak in the Seattle area on Wednesday.

But for this round, at least, we are unlikely to see the flood damage that occurred two weeks ago, the last time the king tides hit.

King tides are extraordinarily high waves that are based on the alignment between the Earth, the sun, and the moon. In the Puget Sound, they happen at intervals during the late fall and winter.

The problem comes when king tides hit in tandem with a low pressure system that brings stormy weather.

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“When we get king tides combined with a nice strong storm moving through with low atmospheric pressure, the lack of suppression from the air going all the way up into space, and all the surf action — wind, waves, and things like that — can really exacerbate the situation,” said KIRO Newsradio meteorologist Ted Buehner.

That is what leads to the widespread flooding that the region suffered in late December. At that time, nearly 50 properties in South Seattle suffered substantial damage when the Duwamish River flooded. Other communities around the Puget Sound region, such as Olympia and parts of Skagit County, suffered flood damage as well.

“That series of king tides had much lower atmospheric pressure over our area, less suppression on the ocean surface or the Puget Sound surface itself, and that allowed the tidal anomaly — the difference between that and the predicted high tides — to be a little higher, resulting in a lot of these low-lying areas getting inundated,” Buehner said.

This time, however, there should not be that level of flooding, because the king tides are not happening during a time of low pressure and inclement weather. An atmospheric river is on the docket later in the week, but the tides will peak before that point.

“This time around, yes, it’s going to be a high tide, but I don’t think you’re going to see nearly as many low-lying areas getting inundated during the high tide period,” Buehner said.

However, that could change in late January, when the king tides will return again. It is, of course, too soon to say what kind of weather will accompany those tides, but emergency responders are already preparing for the worst.

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“We’ve identified several locations along the [Duwamish] riverside where we observed the river overtopping during the December 27 event, and we will be strategically placing sandbags at low points along the river to protect against a similar overtopping,” said Seattle Public Utilities General Manager Andrew Lee.

Lee noted that Seattle Public Utilities and the Seattle Department of Transportation are also investing $100 million into longer-term infrastructure solutions to prevent flooding, such as drainage system and road improvements.

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