Redwood City gearing up for El Nino

The National Oceanic and Atmospheric Association says the region might see strong El Niño conditions this year, and the state is likely to have a wetter-than-normal winter. As a result, Redwood City officials are gearing up to prevent — or respond to — any possible flooding.
During some previous winters, trouble spots for flooding in Redwood City have included the Friendly Acres neighborhood and a nearby stretch of Broadway.

Public Works Director Ramana Chinnakotla recently spoke with the San Francisco Examiner about the city’s storm preparedness strategies. The town has more than 10 miles of canals and creeks enabling storm water to flow to the Bay, and the removal of sediment and vegetation from those man-made and natural waterways has been crucial to flood mitigation.

The permitting process for the work began in January, Chinnakotla noted, because agencies like the U.S. Fish and Wildlife Service must first confirm sensitive species won’t be impacted by the cleanup operations. The work began at the end of the last rainy season and was performed in-house by a team of five employees.

Some systems rely on gravity to drain storm water, but Redwood City’s flood control infrastructure uses 22 pumps, and refurbishing some of that equipment was another part of the town’s preparations.

The city budgets about $250,000 per year for the repairs, Chinnakotla said, noting both diesel and electric pumps are used. And because power outages are not uncommon during storms, the electric pump stations have backup generators, and can function during a blackout, the director added.
The pumps play a key role in preventing floods, enabling city staff to use assets like the 140-acre artificial lagoon at Redwood Shores as temporary repositories for excess rainwater.

“We can actually control the level of the lagoon,” Chinnakotla said, “So in winter, we lower the level by one foot, and the lagoon essentially functions as a detention basin.”

One engineering challenge the city is still trying to solve is the flood hazard facing the Friendly Acres area. The neighborhood, which is south of Woodside Road, is slightly higher than sea-level. Storm water is pumped from the area to the east of Highway 101, where it enters the Bayfront Canal and is discharged to the Bay.

During high tides, however, a tide gate must close to prevent Bay water from flowing into the canal. If a high tide occurs during a severe storm, Chinnakotla explained, storm water trapped in the canal would have nowhere to go, and flooding could result. And because the canal also receives nearby Atherton’s storm water, any remedy would be a multi-city collaboration, Chinnakotla said.

To address that type of need, San Mateo County Supervisor Dave Pine has been spearheading an effort to create a joint power agency to coordinate flood mitigation across the Peninsula’s city and county lines.

Just north of Friendly Acres, the city is prepared to close Broadway from Second Avenue to Charter Street, but Chinnakotla said the possible road closure wouldn’t necessarily mean the street has flooded.

“It’s not that it’s going to be flooded,” Chinnakotla explained, “It’s that water will be in the street, and it’s safer to close it and divert traffic.”

The city has more than 10,000 sandbags available at the Public Works office at 1400 Broadway, for any resident who needs them. And if a homeowner is disabled, or a senior citizen not physically able to stack sandbags, city employees can help.

“If there’s an issue like that, call us. We’ll be glad to help,” Chinnakotla said.

For storm preparation tips, visit www.redwoodcity.org/departments/public-works/storm.

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