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Rising sea level gets city's attention
New report says Bay, creeks would flood Mountain View's job centers
The city's Planning Department is taking seriously a projected rise in the San Francisco Bay's water level that could lead to periodic flooding of much of the Shoreline business district and Moffett Field by 2100.
According to a March 11 report by Oakland-based Pacific Institute titled "The Impacts of Sea-Level Rise on the California Coast," a 4.6-foot rise in sea level predicted by 2100 could make the Bay swell high enough for flood waters to hit the northern edge of the mobile home park on Space Park Way after swamping the Shoreline Amphitheatre, NASA Ames and Google's headquarters.
The 75-acre research park planned at Moffett Field stays dry, however, according to the report.
"The thing about sea level rise is that it doesn't really stop," said Jeff Segall, a chemist who studied the issue as a member of the city's Environmental Sustainability Task Force.
While the Pacific Institute's illustrative flood maps are not intended to replace official FEMA flood maps, the predictions have caught the eye of the city's Planning Department.
"There been several of these maps that have been published," said planning director Randy Tsuda. "One of the things any community needs to look at are the implications of climate change. If sea level rise is a part of that, I think it's our responsibility as city officials to look at what those implications are."
The predictions may prove valuable as the city revises its General Plan, the city's blueprint for future development.
"This is certainly one of the things we need to look at in the General Plan," Tsuda said. "Under the General Plan we are required to address safety issues. Certainly this is a safety issue."
Throughout the Bay Area, 140,000 residents are currently at risk from a 100-year flood event, said Matt Heberger, one of the Pacific Institute report's co-authors. But given today's population, that number would increase to 270,000 in the event of a 1.4-meter sea level rise by 2100.
The report warns that at least 480,000 California residents could be affected in floods by 2100. A wide range of critical infrastructure and almost $100 billion of property would also face an increased risk during a flood throughout the state. But almost two-thirds of the areas at risk in the state are in the Bay Area, the report's authors discovered.
The bathtub effect
Sea level is projected to rise between 1 and 1.4 meters (3.28 to 4.59 feet) by 2100, according to the National Oceanic and Atmospheric Administration. Because of the "bathtub effect," the increase in sea level could mean more storm flooding along Mountain View's Permanente Creek and Stevens Creek, both of which flow into the Bay, Segall said.
"The combination of a lot of water coming down and high tides combine to give you a flood. The sea level rise just makes the overall level higher," Segall said. Neighbors of Permanente Creek north of about Middlefield Road would be most effected, he added.
Peter Gleick, president of the Pacific Institute, believes it could take as little as a six-inch rise in sea level to make 100-year floods happen every 10 years in some low lying areas.
In Mountain View there are 3,170 parcels of property in the 100-year flood zones along Permanente Creek, according to the Santa Clara Valley Water District. Most are north of El Camino Real, but some are near the Los Altos border.
Permanente Creek runs through the middle of Google's headquarters, about a mile from the Bay, where the Internet giant is already planning for flood walls along the creek as it builds a pedestrian bridge over it. Meanwhile, the water district is working on a plan to create flood basins at Rancho San Antonio open space preserve and Blach School in Los Altos, and the Cuesta Annex and McKelvey Park in Mountain View, to help prevent destructive floods along Permanente and Hale creeks.
Last year, several members of the now-disbanded Environmental Sustainability Task Force recommended that the city build housing in the Shoreline area, so that employees, such as those of Google, would rely less on cars. But members of the task force's "Adaptation to Climate Change" working group recommended a building moratorium in the area in light of the future flood predictions. After getting some feedback from the rest of the task force, the climate change group eventually changed its position to say that housing could be protected from flooding if built atop commercial space in the Shoreline area.
"Until there is a plan for the whole area in terms of what the flood protection looks like, I wonder if it's a good idea to add additional buildings," said Segall, who was a member of the climate change working group.
Google has planned a one million square foot building on the northwestern corner of Moffett Field on what used to be wetlands. And several city buildings lie in the predicted flood areas, including several at Shoreline Park and the fire station on Shoreline Boulevard, which is undergoing a major redesign. It will likely be rebuilt using brick and metal construction materials, an asset during flooding, despite its initial high cost.
Design features
"One of the things being looked at is designing buildings so they can withstand flooding," said Will Travis, director of the Bay Conservation and Development Commission. "One of the greatest problems in New Orleans was caused by sheetrock." The older stone buildings were fine, he said, but "newer buildings with sheetrock -- once they got wet they got moldy and had to be torn down."
In terms of city planning for floods, pavement is a major element to consider, said Ann Draper, assistant operating officer with the water district.
"When people pave over the ground you get more runoff," Draper said. "You could have 10 times more runoff if the ground is impervious."
Travis has been trying to raise awareness about the issues of the rising Bay. He says wetlands are "sponges" that help with flood control, but soon there will be no wetlands and the focus will be on saving land and buildings. He is calling for a regional approach to the problem among the Bay Area's 110 municipalities.
Over a year ago Travis talked to NASA Ames employees who were concerned about how the rising sea level might affect their workplace, which is adjacent to the Bay and not far from Stevens Creek.
"It's like the airports, it's going to be protected -- you are not just going to allow it to go under water," Travis said, likening NASA Ames and Moffett Field to the Oakland and San Francisco airports on the edge of the Bay. "It's not as daunting as it would seem at first blush."
Causes of floods
Travis says cities should begin to plan for sudden rises in sea level that could be caused by large ice sheets sliding into the oceans off Greenland and Antarctica.
In Greenland, "The water is actually getting underneath the ice sheet and lubricating it," Travis said. "The concern now is that instead of melting slowly they could melt and slide into the water. Then it would be like taking a glass that's full and throwing some ice cubes in it. That is something scientists are worried about."
Global warming may cause floods another way: It may not bring more rainwater, but scientists are beginning to agree that there could be more intense storms as the planet's temperature rises.
"The growing consensus is that they could be more intense and more flashy," Draper said. "The 100-year flood could be more frequent."
A new report
Local officials are anticipating another report on the rise in sea level: the South San Francisco Bay Shoreline Study. An ongoing joint effort by the water district, the U.S. Army Corps of Engineers and the California State Coastal Conservancy, the report is partly intended to identify areas in need of levees, dikes and other protective measures in light of the rising Bay.
"The levees in the Shoreline area built by Cargill were never meant to be protective levees," said the water district's Draper. She said the Shoreline study will predict flooding out to 2067.
Draper said the Pacific Institute flood projections don't take into account things like creek and salt pond levees, storm drains and pump stations. But "it's a credible, good start," she said. "More study is needed -- we're in the process of doing that" with the Shoreline study, portions of which are due by the end of this year.
Planning director Tsuda said he is anticipating the Shoreline study as well.
"Until that comes out we're speculating," he said.
http://www.mv-voice.com/news/show_story.php?id=1313
