azcentral.com
Olympia looks at effects of rising ocean levels
Elizabeth M. Gillespie
Associated Press
May. 6, 2004 02:15 PM
OLYMPIA, Wash. - The sea is rising, and the city is sinking.
But so far, while some adjustments are being made, no one here is drawing up plans to build dikes and floodgates to keep the waters of south Puget Sound from turning Olympia's streets into streams.
Public works planners and port officials know oceans have been rising at an average rate of nearly half a foot per century, about the same rate tectonic plate movements have been driving down the land beneath the city.
Scientists project that global warming could cause sea levels to rise as much as 3 feet in some places over the next century, but it could be decades before it's clear just how big a problem it might become.
While a new bridge was built higher and a sewer line is being moved inland, other issues for the most part are taking priority now.
"It's a really difficult thing in a policy context. It obviously doesn't compute well with more pressing things where you have a clear and present crisis to deal with," said Douglas Canning, an environmental planner with the state Department of Ecology.
In Seattle, the closest National Oceanic and Atmospheric Administration tide gauge station to Olympia, mean sea level rose about 8 inches from 1890 to 2000. That's about 2 inches above the global average during the 20th century, according to estimates in a 2000 report from the Intergovernmental Panel on Climate Change.
The mean sea level hasn't changed much in the past century at Astoria, Ore., where tectonic plates have pushed the land upward. San Francisco and San Diego have seen about the same sea-level rise as Seattle.
The oceans are rising for two main reasons: Water expands as temperatures rise, just as it does when it freezes. And rising temperatures melt land-based ice, which adds water to the ocean.
In general, the West Coast is considered less vulnerable than areas like the Gulf Coast. New Orleans, for example, already must close floodgates to keep low-lying roads and homes from flooding.
Tides along Washington, Oregon and Northern California's coastline can rise and fall by 10 feet or so in a single day. Shorelines are also relatively steep and rocky. That topography often forces coastal development farther inland and higher in elevation, reducing vulnerability.
However, there are vulnerable stretches of coastline: sand spits, river deltas and estuaries, where the confluence of ocean tides and rivers creates a nutrient-rich environment that supports a vast array of plants, marine life, bugs and shorebirds.
Higher sea levels could slowly decimate those sensitive ecosystems, according to John Rybczyk, a Western Washington University professor who's studying how rising sea levels are affecting Padilla and Willapa bays, two of the largest estuaries in the Pacific Northwest.
"You can't dike them off," Rybczyk said. "They're exposed to the river and the sea. They have to be. They need the nutrients from the water. In a way these systems are the most vulnerable."
In Southern California, researchers at the Scripps Institute of Oceanography fear rising ocean levels could eat away at the wide beaches that define the coastline.
Professor Doug Inman, director of the Center for Coastal Studies at the University of San Diego's Scripps Institution of Oceanography, is working on a computer model factoring in climate-change scenarios that would help planners and policy-makers decide how to protect coastal areas.
In Hawaii, concerns about coastal erosion center more on the battering beaches take from huge storms than from the slow rise of the oceans.
"How do you devote the necessary resources dedicated to some event that may happen in the future when you don't even have the resources to deal with all the problems you're facing today?" asked Sam Lemmo, an administrator with Hawaii's Department of Land and Natural Resources.
Mean sea-level rise in Honolulu, the NOAA tide gauge station with the most reliable data, was about half of Seattle's from 1905 to 2000. Elsewhere, data from stations dating back to the middle of the 20th century show rises in sea-level ranging from about 2 inches below the global average to 2 inches above it.
Olympia has been studying the potential effect of rising oceans for years, and figured out that a 4-foot sea-level rise by 2100 would flood the entire port peninsula and much of downtown - low-lying areas built on fill.
Since then, better climate modeling has lowered the likely sea-level-rise scenario by 1 foot. But engineers also figured out that a major flood would likely rise about 1 foot higher west of downtown than previously predicted. That means the assumptions in the city's 1993 report are still valid, said Emmett Dobey, manager of the policy and program development office for the city's Public Works Department.
Since scientists predict warming will increase the frequency and severity of storms and flooding, it's hard to tell if the bigger problem will be rising oceans or overburdened stormwater systems.
The report outlines several options, including diking, adding more fill and pumping from low-lying areas. But the city hasn't committed to any of those remedies, since it's not clear which one - if any - will work best.
"If you dike or use floodgates and it floods behind it, what have you done?" said Alice Soulek, Olympia's capital facilities planning coordinator.
The city has taken some steps to prepare for higher seas. It's applied for new water rights, since saltwater could contaminate the springs that provide 85 percent of the city's drinking water.
When it had to tear down and replace a bridge linking west Olympia and downtown, engineers built it higher, factoring in both rising sea-level projections and the potential for increased flooding.
This summer, a sewer line along the shore will be moved farther inland, since its present location may one day be constantly submerged, making maintenance more difficult.
At the Port of Olympia, planners and engineers say rising seas aren't a cause for immediate concern because high tide generally falls about 7 feet shy of the docks. But if ocean levels rise 3 or 4 feet in the next century, about half the port's parking lots would flood for about half an hour, twice a year, port engineer Eric Egge predicted.
"That might not be worth millions of dollars to raise the elevation," he said.
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