State's highest tides of year coming this weekend

With an extremely high tide forecast for this weekend, Mason County homeowner Susan Christian has installed plastic tarps and fluid-filled sandbags along the deck of her Totten Inlet house.
With an extremely high tide forecast for this weekend, Mason County homeowner Susan Christian has installed plastic tarps and fluid-filled sandbags along the deck of her Totten Inlet house. The Olympian

When waters start to rise Oyster Bay resident Susan Christian was busy this week preparing for the highest tides of the year, which are expected to hit the shorelines of Puget Sound and coastal Washington Saturday through Monday morning.

She lives in a converted cannery that was built on pilings over the waterfront 65 years ago by J.J. Brenner Oyster Co.

It’s a spectacular setting on the shore of Totten Inlet in Mason County, but it puts her in the path of rare but extreme high tides that occur when the gravitational pull of the sun and moon reinforce each other.

Christian, an art teacher and therapist, had water lapping at her door for the first time in 35 years on Dec. 26. The high tide in Oyster Bay that day was predicted at 17.2 feet. The tides this weekend in Oyster Bay are expected to be 2 to 4 inches higher.

The Christmas event included heavy winds that boosted the waves and accented the high tide, she noted.

“But I can’t take another four inches,” she said. “I’m taking precautions; I’m very vulnerable here.”

With the help of friends, Christian is stacking her furniture off the floor and covering the base of the exterior walls and doors with plastic and plastic bags that work like sandbags, but are filled with water.

“I wish they’d put the pilings in a little higher when they built the cannery,” she said during a break from her preparations.

For most waterfront property owners, the king tides, which are 2 to 5 feet higher than typical high tides, are not that threatening, said Steve Morrison, a senior planner with the Thurston Regional Planning Council.

Of the roughly 2,500 marine residential shoreline properties in Thurston County, about 5 percent are built on low banks that slope up gently from the shoreline. Only a few of those aren’t set back far enough to withstand a high tide.

“That’s not to say people won’t see water over the top of their bulkheads and on their lawns,” Morrison said of the king tides. “And a lot of people have septic tanks in their front yards.”

Homes, wells, septic systems and other private property on the shoreline has been subject to shoreline master planning in this state for about 40 years. The regulations governing how close people can build to the shoreline are in part designed to keep people out of harm’s way during high tides, Morrison noted.

Updated shoreline master programs submitted to the state Department of Ecology by cities and counties for approval are supposed to take into account the possible effect of climate change, in this case rising sea levels, Morrison said.

Global sea levels have risen about 8 inches since the industrial revolution and are expected to continue rising at accelerated rates from global ice melt and gradual warming of the ocean, according to the University of Washington Climate Impacts Group.

While the predictions of the future are not precise, sea levels in Puget Sound could rise anywhere from 3 inches to 22 inches by 2050, according to the UW climate scientists.

“These very high tides are like a window into our future,” said Ecology director Ted Sturdevant. “As sea level rises in the years to come, many of our shorelines – including those in our most populated areas – are very likely to be affected.”

To make this point clear to the public, Ecology officials are urging people to visit their community shorelines and waterfronts this weekend to see the influence of the high tides for themselves. They’re also asking folks to take photos of the high tides and send them to Ecology to help identify areas most vulnerable to tidal flooding.

Downtown Olympia, which looks as though it’s floating on the water during an extreme high tide, is one of those vulnerable areas for several reasons. Puget Sound high tides are highest in the southern end of Puget Sound. In addition, the South Sound land mass is slowly subsiding, adding to the problem of high tides.

Much of downtown Olympia is built on fill and sits just 1 to 3 feet above high tide.

One foot of sea-level rise during extreme high tides would pond on streets and invade low-lying structures, according to a city assessment. Three feet would flood much of downtown at high tide.

The worse-case flooding scenario for downtown Olympia is the combination of a high tide, a heavy rainstorm that swells flows in the Deschutes River emptying into Budd Inlet and a north wind that causes the tide to stack up.

Last weekend, the Deschutes River flows were supercharged by heavy rains, but the state Department of General Administration was able to manage the tide gates at the Capitol Lake Fifth Avenue Dam to release the water into the bay. High tides ranged from 12.6 feet last Saturday to 15.1 feet Tuesday.

“We would have been in trouble if we had this weekend’s high tides a week ago,” said Larry Kessel, General Administration’s dam manager.

The National Weather Service forecast for the king tide weekend calls for seasonal weather systems that shouldn’t produce an additional threat of flooding.

John Dodge: 360-754-5444 jdodge@theolympian.com