The National Weather Service issued an unusual Advisory Monday (Jan. 18th) – this one for a “minor tidal overflow” that will be in effect for Puget Sound Tuesday morning and possibly again Wednesday morning.

According to the report, “very high astronomical tides combined with lower than normal atmospheric pressures” as well as high winds may cause some flooding.

So, if you live near the shoreline and your street/yard/area has a tendency to flood, you might want to put out some sandbags just in case.

Here’s the actual advisory:

… Coastal Flood Advisory for minor tidal overflow is in effect for Puget Sound and the north interior from 5 am to 11 am PST Tuesday…

The National Weather Service in Seattle has issued a coastal Flood Advisory for minor tidal overflow from Puget Sound to the north interior… which is in effect from 5 am to 11 am PST Tuesday.

Minor tidal overflow may occur along some of the shorelines and nearby low-lying areas around Puget Sound and the north interior Tuesday morning… around the time of high tide. Minor tidal overflow is caused by very high astronomical tides combined with lower than normal atmospheric pressures. The Table below shows time of high tide for areas around Puget Sound… along with the normal tide table value and the expected total tide.

Time of tide table expected expected location high tide value anomaly total tide

• Seattle 7:30 am 12.2 ft 1.6 ft 13.8 ft
• Port Townsend 7:06 am 9.1 ft 1.8 ft 10.9 ft
• Bellingham 8:12 am 9.6 ft 1.9 ft 11.5 ft

Minor tidal overflow problems usually begin at 13.5 feet around Seattle and 11.5 feet around Bellingham… and the current forecasts for those areas just meet or exceed those levels. In addition… the atmospheric pressure could be a little lower than forecast… and local winds may cause water to pile up along shorelines more than expected… possibly higher than the expected total tide values. Southeast winds 20 to 30 knots are forecast over the northern inland waters Tuesday morning as another deep low pressure system moves northward offshore. Winds over the waters of Puget Sound are expected to be south 10 to 20 knots Tuesday morning.

Another very high astronomical tide will occur Wednesday morning. The forecast tides for Wednesday morning are slightly lower than for Tuesday… but computer model forecasts indicate the anomaly will still be large enough so that minor tidal overflow problems remain a possibility.

Precautionary/preparedness actions…

Minor tidal over flow can cause local flooding along shorelines and nearby low-lying areas.

WLB Advertiser Vickie Bergquist Insurance Agency wants Readers to know that they have been busy helping renters and homeowners with Flood Insurance.

Regardless of where you live, you can purchase flood insurance.

For most people Flood Insurance is affordable. Many people do not know that Flood insurance also covers mudslide and back up of sewer and drain coverage.

Vickie recommends going to FLOODSMART.GOV for more information on flood coverage.

Vickie’s office stays current on the flood risk and just received this update:

The Army Corps of Engineers reported last Thursday that the repairs at the Howard Hanson Damn have helped, but the risk of flooding is still high.

A new grout curtain constructed by the U.S. Army Corps of Engineers to slow a leak through a damaged abutment at the Hanson Dam will reduce the risk of flooding this winter in the valley to a 1 in 25 chance.

Thousands of giant sandbags along the Green River levees reduces the chance of flooding even more: to 1 in 32 chance.

A heavy rainstorm similar to what struck the Green River Valley last January would overtop the levees and cause flooding in the cities of Auburn, Kent, Renton and Tukwila because the corps will not be able to store as much water as normal at the Eagle Gorge reservoir, the pool of stormwater the corps retains behind the dam.

The corps pumped more than 400,000 gallons of cement to form a grout curtain in the abutment as part of its $8.9 million temporary fix to reduce the risk of flooding. The curtain is about 20 feet wide, 450 feet long and between 90 to 160 feet deep, depending on the location along the abutment.

The corps plans to construct a concrete cutoff wall as a permanent fix within the next three to five years. Crews have started the design process for the concrete wall but the design isn’t expected to be completed until next year.

Wright, from the Corps of Engineers,  praised the work of the cities of Kent, Auburn and Tukwila to place giant sandbags along the levees. The thousands of 3,200-pound sandbags increased the height of the levees to handle a river flow of 13,900 cubic feet per second compared to 12,000 cubic feet per second without the bags.

Wright said that extra height could keep the levees from overtopping if he has to release more water than normal from behind the dam during a storm.

If the corps does have to release water that would cause flooding, Wright said a minimum warning of at least eight hours would be given to local emergency officials who might have to order evacuations. It takes eight hours for water released from the dam to reach Auburn.

For more information, visit Vickie’s website here.

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