Monday, August 6, 2007

Acting Locally - My home turf

As I've posted before, I live close by the San Francisco Bay, about 30 feet in elevation above where a small creek enters an estuary of Richardson Bay. A good part of Mill Valley is flat, barely above sea level, as are many other residential and business neighborhoods in Marin County, and some sections of the one main traffic artery that runs north-south through the county - Route 101, "the redwood highway."

The San Francisco Bay Conservation and Development Commission has done some studies of the impact of sea level rise and reported early this year on its findings. Relevant to where I live, it tells us (according to the Independent Journal, the county newspaper):

Sometime over the next century huge shoreline swaths of Marin, including Hamilton Field, Highway 37 and the Tamalpais Valley could be under water if global warming causes the bay to rise by a meter, according to the San Francisco Bay Conservation and Development Commission.

Additionally, wild and extreme swings in the climate brought on by warming could have an impact on Marin's water supply.

There's an illustrative map of my immediate environs (I live in the upper left corner) and where the new water would spread with a one-meter rise in sea level. I know the intersection below my house would be under water at high tide, blocking one of two main thoroughfares into Mill Valley.

The county is already warning that our once-secure local water supply (unlike most of the state, we have never needed to pipe in water from a distance) is now proving inadequate to supply the growing population of mostly high-priced homes and landscaping. So we face the expense and experimental nature of a desalination plant on the Bay shore.

Over the course of the 25 years I've lived here, I've watched weather maps from the rest of the nation and confirmed for myself that our weather is among the most stable and mild. When that changes, we will surely notice.

This report from the U.S. Geological Survey describes the impact of an El NiƱo-generated rise in sea level on the S.F. Bay Area in the winter of 1998.

Throughout the first week of February 1998, high winds and heavy rains combined with abnormally high tides to wreak havoc in the San Francisco Bay region. The Pacific Ocean surged over parking lots and the coastal highway at San Francisco's Ocean Beach, and whitecaps up to 6 feet high splashed over the city's waterfront Embarcadero for the first time in recent memory. Elsewhere, U.S. Highway 101 north of the Golden Gate Bridge was flooded by as much as 4 feet of water from San Francisco Bay, and other low-lying areas around the bay were also swamped, forcing hundreds of people to flee their homes.
So it's not like we haven't been warned by experience. To our credit, Mill Valley has a helpful Web site about disaster preparedness. Though it doesn't address sea level rise, it does provide good instruction for preparing for wildfires, floods, landslides, storms and earthquakes.

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