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In The News

Peninsula cities must plan for rising sea levels

Bill Paul, Redwood City Daily News, 7/22/09

A few years back I began writing a sci-fi novel that began by portraying a Peninsula in the throes of global warming — ocean water had crept up over the lowland areas, storms had increased in severity, and those who hadn’t moved further inland housed themselves in communities on the tops of the coastal hills. In one scene the hero bikes back down into San Mateo to visit the home where he grew up. Water now stands a yard or two deep all over the neighborhood, and every home is boarded up and condemned.

Even though I pushed the envelope for dramatic effect, one trend is clear — the ocean is indeed slowly rising (8 inches over the past 100 years) and just how much more and how fast is a guessing game. One figure I hear a lot is a rise of 55 inches over the next 90 years. All this water is coming mostly from melting ice in faraway places like Greenland and the Arc­tic Ocean, and the melting is accelerating.

This isn’t just a concern for academ­ics and people like Al Gore.

Because many of us live near the ocean or the Bay, it’s a problem that will come home to roost.

What would happen if the sea level along our Bayfront suddenly rose 55 inches? Due to our moon-generated tides, we already have wide fluctua­tions in our local sea levels. For example, tide charts show that today at Redwood City, the difference between highest and lowest tides will be an impressive 8 feet. Suddenly add 55 inches and we would have a high tide of 12 ½ feet. I’m not sure that every part of the Bay is ready for that much water on a regular basis.

Of course, ocean level increases would happen slowly, only around a half inch per year. That’s just enough to make politicians and planners resist taking ac­tion by putting sea level rises on the back, back burner.

However, with Hurricane Katrina and New Orleans, we’ve seen what happens when levees, channels, pumping stations and other defenses aren’t up to the job during extreme conditions.

In the foreseeable future, it’s the ex­treme conditions that sea level rise could exacerbate, particularly in San Mateo County. The Pacific Institute has a Web site with satellite maps showing Bayfront areas from San Francisco International Airport down into Mountain View. The maps readily depict present flooding pos­sibilities during the “one in one hundred” scenario. That simply means that each year presents a 1 percent chance of a powerful “perfect storm” where, I assume, a huge deluge of rain coincides with high tides and waves. The maps show that a storm of this magnitude would flood SFO, cover portions of downtown San Mateo along with long stretches of the low-ly­ing Highway 101, all of Foster City and Redwood Shores, the Cargill salt flats area (where a large development is proposed), Highway 84 leading up to the Dumbarton Bridge, a good share of East Palo Alto, and half of Moffett Field.

The maps then go on to show how much farther inland the flooding could extend to if the sea level rose 55 inches due to global warming. In San Mateo, the water would now reach El Camino Real in some places. Typically, between San Ma­teo and Mountain View, flooding would extend an additional one-fourth to half mile farther inland with the sea level rise.

Other than the one-in-one-hundred storm, though, sea level rises of 55 inches would present more daily, prosaic prob­lems. Eastward-flowing creeks from the coastal hills would also rise 55 inches as they approach the Bay, probably increas­ing the salt content of the water and changing the water ecology. There would also be more salt water intrusion into underground water tables.

Our present-day Bay wetlands, or salt marshes, would gradually be submerged, unless by some miracle they managed (like coral reefs) to keep building up organic ma­terial to stay above water. If we lose wet­lands, we lose wildlife habitat, the water-fil­tering action of the plants, and their ability to help shield Bay shores from storm-wave action. Some local wetlands are currently being restored, and the proposed Saltworks development in Redwood City would add hundreds of acres of marshes. If sea levels are rising, though, much of the money sunk into these efforts could be just that — sunk under rising water.

Rising sea levels could inundate existing, low-lying waste-water treatment plants, and that would be a pungent devel­opment indeed. Existing storm-drainage systems that feed into the Bay by gravity feed could be compromised.

On the ocean side of the Peninsula, higher sea levels would mean more cliff erosion, with homes and roads lost to the pounding surf.

On the Bay side, the usual answer to flooding threats is levees, and pumps in places like Foster City to remove rain­water runoff. Levees are just piles of dirt, right? A lengthy paper by the state of the California Climate Change Center states that new levees between 10 and 20 feet in height would cost about $1,500 per linear foot in year 2000 dollars (when inflation adjusted, $1,860 per foot). A mile-long levee, then, would cost approximately $10 million. More robust seawalls would cost about $34 million per mile.

Rising sea levels and increased flood threats could mean that SFO would need to be elevated, along with rail lines and low-lying major highways. All this means deciding where to spend scarce taxpayer dollars by prioritizing projects. The California Climate Change Center paper makes the point that areas with low-in­come populations might well get the least protection, just as poor sections of New Orleans didn’t get the flood-protection measures they deserved because they lacked political clout.

At any rate, my sci-fi novel hasn’t pro­gressed past chapter two. However, if I live long enough, I may get to see some of the novel play itself out in real life. Ice contin­ues to melt and the global bathtub’s faucet is trickling. Government and politicians need to be looking to the future to protect populations and infrastructure against flooding, just as preparations have been made to prepare for strong earthquakes.

 

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