As King tides arrive in Western WA, here’s what to know

Communities across the Puget Sound area are preparing for high waters and potential flooding as king tides are forecast to raise waters early Monday, Tuesday and Wednesday mornings.

This week’s king tides, or the highest tides of the year, come less than a month after a king tide brought the worst flooding that Seattle’s South Park neighborhood had seen in years, leaving at least 13 homes flooded on Dec. 27.

On a smaller scale, seawater swamped shoreside parks and homes in King, Whatcom and Snohomish counties.

The National Oceanic and Atmospheric Administration does not expect the king tides this week to cause heavy flooding.

The widespread flooding on Dec. 27 was caused by a storm system that delivered strong winds and heavy rains across the region, as well as unusually low sea-level pressure.

The low pressure caused the water in Puget Sound to bulge upward, creating a strong storm surge, NOAA said.

The sea-level pressure at Seattle-Tacoma International Airport was 978.3 millibars on Dec. 27, the seventh lowest on record. This pressure alone is estimated to have contributed over a foot of surge waters, according to NOAA.

In the king tide event this week, many of the factors that were present in December will not occur, NOAA officials said in an online webinar.

High tides are predicted through January 27 with king tides the mornings of January 23-25. These king tides will be coupled with a higher-than-normal surface pressure, which will have the opposite effect of December’s king tides by reducing storm surge levels.

This round of king tides also is not expected to include “much in the way of winds, wind-driven waves, river levels, heavy precipitation, snow melt or anything else that would contribute to higher-than-usual water levels,” said Reid Walcott, a meteorologist with NOAA.

“While some minor tidal overflow is possible due to just the astronomical tides themselves, the water levels are not expected to reach anywhere close to the levels seen Dec. 26 and 27,” Walcott said.

To prepare for this round of king tides and potential flooding, Seattle Public Utilities, the Seattle Department of Transportation and the city of Seattle’s Facilities and Administrative Services Department have set up temporary flood barriers (concrete blocks, jersey barriers and sandbags) along the Duwamish River and in South Park.

Seattle Public Utilities has coordinated with South Park residents and businesses to organize sandbag pickups and dropoffs, a spokesperson said.

In addition to temporary flood barriers, Seattle Public Utilities is also in the process of improving drainage and building a pump station in South Park, where high waters are common due to its location on a river flood plain.

When completed, the station will pump stormwater from South Park’s lower industrial basin into the lower Duwamish waterway, preventing water from backing up in pipes during high tides, which can cause flooding, SPU said online.

Other drainage-related projects in South Park include added stormwater infrastructure and the South Park Drainage and Roadway Partnership with the Seattle Department of Transportation, which will be completed this year, Seattle Public Utilities said.

A state-led project encourages people to upload photos of king tides or other high-water events online at mycoast.org/wa. The documentation helps scientists, local planners and others understand how sea-level rise and storm surges affect local infrastructure and ecosystems.

NOAA catalogs king tides in the U.S. and other tide predictions for states and regions at tidesandcurrents.noaa.gov. The agency also publishes seasonal projections for high tides.

Seattle Public Utilities asks anyone experiencing urgent but non-life-threatening flooding to call its 24/7 operations response center at 206-386-1800.