By James Temple
19 January 2013

(San Francisco Chronicle) – On a sunny Friday afternoon last fall, a Grand Banks trawler idled at the mouth of Richardson Bay, giving those aboard a close look at a battleground in the fight against climate change.

The lobster claw-shaped estuary defines and occasionally redefines the southeastern edge of Marin County, a shoreline area dotted with expensive homes, shops and restaurants. During the king tides near the turn of the year, when sea levels reach their zenith, water overwhelms the banks and marshes, flooding parts of Shoreline Highway and other roads.

That susceptibility makes Richardson Bay a canary in the coal mine of Bay Area sea level rise. As global warming threatens to transform today's high tides into tomorrow's low ebb, those inconvenient floods could turn into tragedies.

But the estuary's vulnerability also makes it an ideal site to try bold approaches to shoreline protection.

Which is why architects Elizabeth Ranieri and Byron Kuth chartered the trawler that October afternoon. Peering out from beneath sunglasses and baseball caps, they surveyed the stretch from Sausalito to Belvedere and imagined their designs for an entirely new kind of levee, a barrier with porous walls that could protect the shore as well as the ecology of the bay. "Sea level rise is essentially right around the corner," said Kuth, a husky man with a reddish goatee. "We have to begin to think now about how we introduce innovative ideas."

The oldest continually operating tidal gauge in the Americas descends into the shores along Crissy Field in San Francisco, tethered beneath a breakwater that doubles as a nest for Elegant Terns. The original instrument and its descendants have recorded the ebb and flow of coastal sea levels since 1854, when the United States Coast Survey installed it to help ships navigate the treacherous Golden Gate.

Over the last century, the gauge has tracked a gradual 8-inch rise in coastal waters. But by 2050, as global warming melts ice caps and swells the seas, the gauge's readings could leap almost 1 1/2 feet, scientists say.

For Bay Area residents, it will be one of the most obvious effects of a changing climate. Not just Richardson Bay, but land equivalent in area to six San Franciscos could regularly flood, inundating vast swaths of the region's airports, high-tech campuses and the homes of more than 100,000 residents, according to the San Francisco Bay Conservation and Development Commission.

And the toll will only climb from there, with sea levels expected to surge as much as 6 feet by 2100.

Ultimately, there are few good options for confronting this challenge.

"There are two reactions to dealing with sea level rise; there is fight and there is flight," said Will Travis, senior adviser to the Bay Area Joint Policy Committee, which coordinates planning efforts among regional agencies. [more]

Preparing the bay for rising sea levels



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