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September 11, 2007
1. Top Item
Rising seas called Delta risk; Warming could leave areas swamped, planners told
Sacramento
By Matt Weiser, staff writer
Children born today could live in a different kind of
It may sound far-fetched, but that could be the outcome of the latest prediction of rising sea level caused by global warming. It's one of the scenarios driving a multipronged effort to plan the future in the Sacramento-San Joaquin Delta.
Last week, the Independent Science Board of the CalFed Bay-Delta Authority said planners should prepare for 28 to 39 inches of sea-level rise by 2100. That's double the most widely accepted current estimates.
On Monday, new data were presented on how a rise that large may affect the Delta and nearby communities.
Using aerial imaging that reveals surface elevation, Noah Knowles of the U.S. Geological Survey said a 39-inch sea level rise, equivalent to 1 meter, would inundate more than 380 square miles on the edges of the Delta. This could include
"It's noteworthy that they're going to have to be even better protected if this scenario plays out," said Knowles, a research hydrologist who spoke Monday at the California Climate Change Conference in
Knowles said the data were developed just a week ago and need more analysis. For instance, he has not yet examined effects on the 1,100 miles of levees protecting more than 70 islands within the Delta.
Many of those levees could be overtopped by a 39-inch sea level rise, especially when combined with high tides and storm-driven waves and river flows.
"The question in the Delta is whether those levees will hold," Knowles said, "and whether continuing to protect those is the correct policy."
That question is being addressed by researchers and state officials in several ongoing projects. A report on protecting the estuary is due in November from the governor-appointed Delta Blue Ribbon Task Force. And the state Department of Water Resources is drafting a strategy to guard against climate change, earthquakes and storms.
Providing input to both groups is the CalFed Bay-Delta Authority, a coalition of state and federal agencies. Last week, its 11-member Independent Science Board issued a report advising all those researching the future of the Delta to prepare for a sea level rise of up to 39 inches by the end of this century. That is double the last estimate by the Intergovernmental Panel on Climate Change, the worldwide body developing global warming scenarios.
Jeff Mount, a UC Davis geology professor and chair of the CalFed science board, said the science of sea level rise has made big strides in the past year, so methods used by the IPCC are no longer best.
New predictions use computer modeling based on actual sea level rise documented so far, which grew from an average of 2 millimeters per year before 1990 to 3.5 millimeters since then.
The new method is more accurate, Mount said, than previous models that use mathematical formulas to predict sea level.
If waters rise 39 inches this century, many levees in the Delta could be overtopped, creating vast areas of open water that would be hostile to native wildlife. Seawater could intrude much farther into the Delta from the ocean, damaging a water supply that serves more than 23 million Californians and millions of acres of farmland.
At a meeting last month, the DWR strategy group presented preliminary cost estimates for some of the features under study.
The most controversial is a 44-mile peripheral canal that would funnel a portion of Sacramento River water directly to state and federal pumps near
An alternate approach is a 48-mile corridor of reinforced levees to move export water through the Delta. The early estimate is $9.8 billion.
The rest of the Delta would still need lots of work. Strengthening just 100 miles of levees on seven islands in the west Delta -- considered critical to water quality and infrastructure -- could cost an estimated $8.1 billion, researchers said.
But none of these estimates accounts for sea level rise, which would require levees to be raised, at a cost of billions more.
Les Harder, DWR deputy director, said the strategy group will include new estimates next time, and it is now discussing what depth of water to anticipate.
"The sea level rise will exacerbate all the other issues," said Harder.
Mount and Knowles both said the predictions are fraught with uncertainty. One is that there is not yet a way to measure melting ice sheets on Greenland and
Mount said scientists have "high confidence" that sea level will rise, but "modest confidence" about how much.
Living with these changes will be difficult. Scientists say there is still time to moderate effects by reducing gas emissions from transportation, energy and manufacturing processes.
In
"If we have the possibility of putting hundreds of thousands of more people at risk in the future," she said, "that's probably short-sighted, and we should be careful as a state to be sure we're not putting more people in harm's way." #
http://www.sacbee.com/101/story/372195.html
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