Publication Date: Friday Oct 17, 1997

FLOOD CONTROL: Creek design error angers residents

About 60 Barron Park residents and other Palo Altans who live near creeks confronted water district officials Wednesday about a design error that undermined part of a flood control project that was intended to protect their homes. The project was expected to prevent a flood of a size that would be expected to occur just once in a hundred years, but instead it can withstand only floods that are twice as likely.

The residents gathered at Hyatt Rickeys in Palo Alto and listened as officials of the Santa Clara Valley Water District explained how a mistake was made in calculating how high to make the Louis Road bridge over Matadero Creek. That error resulted in the bridge being built too low to withstand a 100-year flood.

That means that if enough water hit the bridge, it would surge back, flooding neighborhoods upstream.

The problem is complicated by the fact that the water district built a diversion channel to carry even more water into Matadero Creek from neighboring Barron Creek in the event of a large flood, but now that diversion may be too dangerous to use.

"This is a problem that I've inherited," said Greg Zlotnick, a water district board member who grew up in Palo Alto. "I'm not pleased about it," he told the audience. "The reality that we're dealing with is that we've got a problem, and the solutions don't necessarily make everybody happy."

Dave Chesterman, head of the water district's design team, said his staff discovered the problem this month as they were reviewing capacity calculations. The error was actually made in 1988, when the $22 million Palo Alto flood control project began, he said.

"The goal (of the project) was to eliminate all the area from the 1 percent (100-year) flood. We did not achieve that goal," Chesterman said. "There was a problem in the analysis of the creek in the lower reaches of Matadero around Louis Road. The area along Matadero Creek from Waverley to 101 does not have 100-year protection, it has 50-year protection."

(A 50-year flood has a 2 percent chance of occuring in a given year.)

If there were a 100-year flood, flooding would most likely start at Waverley Street in south Palo Alto, causing new danger to homes not yet designated on official flood maps. "It would be sudden. The water would rise to the bottom of the bridge," he said, then a "surge in the water would overtop the flood walls." It could be flowing as fast as 500 cubic feet per second.

The last time there was severe flooding in Palo Alto was in 1983 in Barron Park. That flood was a 17-year flood, or one that has one chance in 17 years of occurring. "If this happened now, it would safely pass through the system," Chesterman said.

This winter, solutions are fairly limited, officials said. They range from doing nothing, which would leave Matadero Creek with 50-year flood protection, and Barron Creek with 100-year protection, to blocking the Barron Creek diversion, which would give Matadero Creek 100-year protection but would leave Barron Creek with only 5-year protection, the same as before the project.

Other options, such as partially blocking the diversion or raising the Waverley Street flood wall, would spread risk between the two creeks.

Los Robles resident Ken Poulton asked why the district couldn't simply remove the Louis Road bridge, considering "the cost of dealing with the bridge versus the cost to all the homeowners around. This is, to put it frankly, this is your screw-up."

Assistant General Manager Kay Whitlock told the audience that all ideas would be brought back to the water district board on Tuesday, even the idea of removing the bridge.

The Santa Clara Valley Water District board will discuss the Palo Alto flood control problems at its next meeting, Tuesday, Oct. 21, at district headquarters in San Jose. The board is expected to make a decision on a plan of action as soon as its next meeting, Nov. 4.

For more information, call (408) 265-2600. A memo to the board about the two community meetings is expected to be posted on the water district's Web site, at www.scvwd.dst.ca.us, before Tuesday. 

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