Living with water

GREEN CITY: By the middle of the century, the waters of the San Francisco Bay could rise up to 16 inches
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rebeccab@sfbg.com

GREEN CITY Here's a sobering thought: By the middle of the century, the waters of the San Francisco Bay could rise up to 16 inches. By 2100, in a worst-case scenario, the water level could creep up 55 inches higher, affecting some 270,000 people and placing economic resources worth $62 billion at risk.

These projections, which are potential consequences of climate change, are outlined in San Francisco Bay: Preparing for the Next Level, a joint report issued by the San Francisco Bay Conservation and Development Commission (BCDC) and a team of Dutch research and engineering firms.

The Dutch have centuries of experience with flood mitigation. The low-lying, flood-prone territory of the Netherlands, adjacent to the North Sea, has forced Dutch engineers to become well versed in utilizing dikes, levees, and other adaptive techniques to contend with sea-level rise.

Drawing on that expertise, the San Francisco Bay study serves as a wake-up call and the beginnings of a roadmap for the Bay Area, listing 60 possible measures for addressing what appears to be an inevitable rise in sea level. Ideas range from sturdy levees, to mechanical floodwalls, to innovations such as floating houses.

"Adaptation is essential because it's really too late to stop climate change and sea-level rise," Will Travis, executive director of BCDC, noted at a Sept. 21 symposium held to discuss the study. "If we shut down all the power plants, turn off all the lights, and park all the cars today, it'll still continue to get warmer for at least a half a century or more."

Even with the world's flood-mitigation experts on the case, the scenarios are daunting — and the implications are only beginning to come into focus for policymakers, planners, and the urban populations who inhabit coastal territories.

Waves in the bay could swell to about 25 percent higher on average. Intense storms are also expected to happen more often. If the sea level rose one foot, for instance, a storm-surge induced flood that used to occur roughly once a century would instead happen once a decade. The changes would be accompanied by an air-temperature increase of more than 10 degrees by 2100 — the difference between a typical summer day and a typical winter day in San Francisco.

"The reality of sea-level rise needs to be taken seriously," San Francisco Board of Supervisors President David Chiu, who delivered remarks at the symposium, told the Guardian. Chiu represents San Francisco on BCDC, one of the few bodies that can bring multiple stakeholders from throughout the region under one tent to plan for sea-level rise.

If the sea level in the San Francisco Bay rose three feet, some critical landmarks — Treasure Island, AT&T Park, and San Francisco International Airport — would end up underwater unless mitigation measures were in place.

Treasure Island, the site of one of the largest redevelopment projects currently moving forward in San Francisco, was cited in the report as a case study "for how large-scale development projects can deal with rising sea levels." Project developers are looking at artificially increasing island elevation to accommodate a three-foot rise in water level, according to Jack Sylvan, director of joint development for the city's Office of Economic and Workforce Development.

Plans also include creating a buffer between new construction and the high-water line, and leaving open the possibility of shoring up the perimeter if it's necessary to prevent flooding in the future, he said. "The fact that it's an island forces us to address the issue," Sylvan told the Guardian.

In the report, proposed strategies for coping with climate change were presented along a continuum.