Olympia in risk zone for rise in sea level

By John Dodge | The Olympian • Published January 18, 2008

Olympia remains one of the more vulnerable areas in Puget Sound in the latest estimate of sea-level rise caused by climate change and melting glaciers.

Sea levels in the Puget Sound Basin are predicted to rise anywhere from 3 inches to 22 inches by 2050 and 6 inches to 50 inches by 2100, according to a report released Thursday by the Pacific Northwest Climate Impacts Group and the University of Washington and state Department of Ecology.

The most likely scenario is 6 inches by 2050 and 14 inches by 2100, the study says.

Previous projections used by Olympia officials to predict sea-level-rise effects on downtown Olympia were 1 foot of sea level rise by 2050 and 3 feet by 2100, which fall between the moderate and worse-case scenarios in the latest report.

Under extreme high tides, 1 foot of sea-level rise could create pools of water on some city streets and flooding of low-lying structures, according to a September 2007 report prepared for the city. A 3-foot sea-level rise could flood most of downtown during extreme high tides, which occur once or twice a year.

Olympia officials are reacting to the warnings. The city paid two high-profile authors, Andrew Revkin and Terry Tempest Williams, $12,500 apiece plus travel and lodging to be guest speakers at a Climate Change Forum last year. And this year’s budget includes $30,000 to create a climate-change task force to follow up. It is unclear what the solution will be to protect downtown from flooding.

In the past two decades, the city has worked on not adding to the problem by reducing vehicle emissions, using green power for city utilities and moving toward zero waste.

City senior program specialist Vince McGowan summed up the sea-level-rise threat on the city’s Web site. “If no protection measures are taken, the 1 foot of sea-level rise predicted by 2050 would result in ponding on some streets and flooding of low-lying structures during the extreme high tides that occur once or twice a year,” he wrote. “A 2-foot rise would impact an even greater area. Pipes designed to convey stormwater away from downtown would be unable to discharge fast enough to prevent flooding during storms. At higher levels, flows would reverse, and the sea would flow out of street drains and into the streets.”

South Sound remains the most susceptible region to sea-level rise because tides are higher here than other areas of the Puget Sound, noted Philip Mote, a UW research scientist and lead author of the report.

Mote also said the latest research raises doubt about whether the South Sound land mass is subsiding as previously expected. A drop in land mass would exacerbate flooding caused by sea-level rise.

The report is intended to help planners and elected officials factor in sea-level rise when they make land-use decisions.

“If you have a high-value project and low risk tolerance, then you want to plan for the worst-case scenario,” Mote suggested.

Olympian reporter Matt Batcheldor contributed to this report.