These San José Floodwalls Should Shield Neighborhoods Against a 20-Year Flood

Nearly eight years to the day after major flooding displaced thousands in San José, officials on Thursday celebrated the completion of almost 9,000 feet of new floodwalls to help shield neighborhoods.

South Bay leaders stood inside a newly enclosed patch of land in the city’s Olinder-McKinley neighborhood, highlighting one of seven areas between Highway 280 and Old Oakland Road that are now equipped with 10-foot steel walls, many encased in concrete.

“Eight years ago, residents of this neighborhood had to rush to leave their homes during the worst flooding in this area experienced since 1997,” Richard Santos, the vice chair of the Santa Clara Valley Water District’s Board of Directors, said during Thursday’s gathering. “This was a devastated area.”

The height and strength of the new barriers are meant to hold back heavy water flows during a 20-year flood event, a term used to refer to an intense flood that could happen once every 20 years or has a roughly 5% chance of happening in any given year.

The walls represent the first phase of Valley Water’s Coyote Creek Flood Protection Project, which will ultimately cover several points across an eight-mile stretch along the creek between Montague Expressway and Tully Road in San José.

The project is also tied to a massive renovation and seismic retrofit underway at Anderson Dam in Morgan Hill, which could increase the flows into Coyote Creek when storm surges occur to stop the dam from overflowing.

The seven areas that were chosen for the first phase of walls are considered the most vulnerable to flooding because they are low-lying and are near sections of the creek where additional water would flow after a tunnel diversion portion of the dam upgrade is completed.

Officials said the walls, which will vary slightly depending on where they are installed, can withstand a storm surge like the one seen on President’s Day weekend in 2017, when rushing waters overtopped the banks of Coyote Creek, overrunning parks, roads and homes, and triggering evacuation orders or advisories for tens of thousands of people.

“I think those of us who were living here in San José in 2017, we all have some sort of personal story,” Valley Water board member Shiloh Ballard said during the announcement. “We know someone, or we experienced it personally.”

The city of San José faced significant criticism in the days and months after the flood, including in a report it commissioned that gave the city an “F” for its level of foresight regarding the storm. The report also lambasted its late notification to many residents, some of whom received evacuation orders after floodwaters were already at their door.

Saraí Rojas, a resident of the Olinder-McKinley neighborhood, lives in an apartment near the creek and said she is happy to see the floodwalls largely completed near her home.

“It’s important work. I want to think it’s a good use of tax dollars … because, though I didn’t live here in 2017, I’ve seen the pictures and the extent of all the damage. I’m also a firm believer in climate change,” Rojas said. “So anything that we can do to kind of assuage those negative impacts, I’m all for.”

Rojas has also received flood-ready pamphlets and information from the water district and said she tries to stay vigilant during wet weather.

Santa Clara County Supervisor Betty Duong said the work being recognized this week is about more than just managing waterways.

“Whenever we talk about the flood of 2017, when we talk about the impending doom of future potential floods, we see people and families. And that’s what it comes down to,” Duong said. “When floods happen time and time again, it is always the most vulnerable families, seniors on fixed incomes, families with small children, who are going to be suffering the most.”

The first phase of Valley Water’s project cost about $117 million, officials said, and the next phase, which would add about 17,000 more feet of walls, passive barriers and earthen berms, is estimated to cost $221 million.

Robert Yamane, the lead project engineer, said the passive barriers will be made of aluminum interlocking structures that will lay flat until water levels rise.

“It’s around park areas, so people can still get into the park, and it’s not blocking all lines of sight into the park,” Yamane said. “So they lie down flat, kind of adjacent to the sidewalks, and then they’ll float up and then lock into place with some struts.”

Chris Hakes, chief operating officer of watersheds at Valley Water, said the water district attempted to plan a project in 2011 in conjunction with the Army Corps of Engineers that would have offered a significantly higher level of protection — enough to withstand a 100-year-flood — but the costs were too high in the view of the Corps, and the project was scrapped.

He said residents and business owners in the areas with the new walls have been patient and supportive of the current project, which has been a long time coming.

“There are many community members here who are breathing a little bit of a sigh of relief that this project is completing,” he said, “and they’re getting the protection that they’ve sought for a long time.”