Sea level rise is long-term challenge for downtown

Scientists estimate that sea levels will rise by three to four feet by the end of this century, even if there is substantial progress in the next few decades in reducing greenhouse gas emissions.

That puts downtown Olympia in the path of significant flooding unless the city takes dramatic actions to protect it. Planning for sea level rise has been discussed by the City Council since 1990, and since 2008, the council has received annual updates as engineers figure out what areas will need protection and how that could be accomplished.

The city has adopted a policy to protect downtown and prepare for 50 inches of sea level rise. But in a recent City Council work session, Eric Christensen, the city’s public works manager, noted that estimates of the extent of sea level rise keep going up. The Army Corps of Engineers predicts as much as five feet by the end of this century; the National Oceanic and Atmospheric Administration predicts up to six and a half feet.

Locally, El Nino weather events that bring heavier rains are likely to make it worse, particularly at high tides.

Even if greenhouse gas production is reduced, sea levels will continue to rise far beyond 2100. The council’s newest member, Clark Gilman, wondered if we should plan to retreat from downtown and move the central business district uphill.

But Christensen displayed a broad array of measures that can protect downtown, ranging from re-configured storm-water systems to sea walls, elevated roadways, new building requirements, raising the land around Capitol Lake, and keeping the Fifth Avenue dam in place. He reported that these measures, which could protect downtown from a three- or four-foot sea level rise, are estimated to cost about $60 million, but would protect, among other things, the LOTT sewage treatment plant, in which we’ve invested about half a billion dollars.

So it seems reasonable — if extremely expensive and complicated — to plan to preserve downtown for the rest of this century, and to keep updating the plan in the decades ahead as we see how accurate today’s estimates of the problem prove to be.

Doing this requires an eyes-wide-open recognition that we have no time to waste. We need focused planning, public discussion, and major expenditures.

Even if we succeed at implementing the measures that will protect downtown for the next few decades, it may not be enough to protect it for future generations.

If, as predicted, sea level rise eventually overwhelms the protection that on-land engineered solutions can provide, an immense structure, similar to a canal lock, could create a gated barrier across Budd Inlet north of the port peninsula. Similar structures are being built to protect Venice and other cities, and have been a mainstay of the Netherlands and other low-lying regions of western Europe. The cost and environmental impact of such a solution is hard to imagine.

This is a lot to worry about. The uncertainty of the scientists’ projections, the lack of public understanding of the issue, competing City Council priorities, and lack of funding make this a Gordian knot that only bold, sustained work can untangle.

Clearly, the city will need help from the federal and state government to protect downtown. In a country that can’t even maintain the most basic infrastructure of safe bridges, highways, and drinking water systems, that may be the most daunting obstacle to overcome.

This story was originally published March 3, 2016 at 4:01 PM with the headline "Sea level rise is long-term challenge for downtown."