Redwood City studies sea-level rise

Mayor Jeff Gee said addressing flooding, sea-level rise and groundwater concerns will be a long-term effort, but it can only start with these studies of gaps in the city’s infrastructure and steps forward.

“This is a regional effort, we’re not going to solve Redwood City by ourselves,” Gee said. “This is a beginning, to socialize the importance of this, we have to learn more.” 

Though exact sea-level rise scenarios cannot be entirely predicted due to unknown specifics about the impact of climate change, Matt Brennan, an engineer with the Environmental Science Associates, a consultant for the city, said it is likely to see sea-level rise between 2 and 7 feet by 2100. 

Target planning for adaptation by 2050 considers accounting for nearly 3.5 feet by the turn of the century. 

Measures to mitigate flooding already exist around the Bay, such as levees and flood walls, but addressing groundwater-related flooding will require further studies and financial considerations, Brennan said. 

The Redwood Shores Peninsula is of particular emphasis, and sits behind a levee that was previously accredited by the Federal Emergency Management Agency until 2019. Redwood City will be commencing a planning and preliminary design study for the area’s levee system. 

Vulnerabilities of other areas included the downtown water reach from the eastern end of the San Carlos Airport, along the shoreline behind Bair Island, and to the west bank of Redwood Creek. Shoreline elevations in this stretch are variable, as are those upstream from Redwood Creek’s east bank. The fourth area considered included the Friendly Acres area with the Bayfront Canal. 

Primary adaptation strategies for each studied area all include raising the shoreline to a higher elevation to meet mitigation standards. Additional strategies presented include maintaining existing marshes — which is a nature-based solution for addressing sea-level rise impacts through wave, erosion and flood attenuation — and improving existing stormwater infrastructure. 

The Bay Conservation and Development Commission’s Regional Shoreline Adaptation Plan will be finalized by the end of the year, which will provide local guidance on collaborative adaptation actions. Regional collaboration will be essential for future planning, Councilmember Alicia Aguirre said. 

“The message I’m hearing and that I’ve learned, it really is a regional effort,” Aguirre said. “We can do patches and pieces, but water doesn’t know borders, cities or counties.” 

Aguirre added the sobering cost of these initiatives, “for a lot of things that have been man made,” but grant opportunities will help mobilize the effort to begin. 

Grants through FEMA are being used for levee planning and flood mitigation, and further funding is being sought after for implementing BCDC’s suggestions and studying the Bayfront Canal’s drainage.  “I’d love to be able to find you the money you need,” Councilmember Diane Howard said. “The price tag is astronomical, but I guess we’ll take it off in bits and pieces and chunks and try to get what we can when we can.” 

Considering the high ticket price for future adaptation efforts — cost estimate is nearly $600 million — Vice Mayor Lissette Espinoza Garnica said it will be critical to focus efforts on areas who may face the most devastating impact of climate change.

“For the next decade or so, while it’s such a difficult time to secure over half a billion dollars in infrastructure cost, that we try as much as possible, if not for the most part, to be investing in the equity priority areas,” Espinoza Garnica said. 

Councilmembers discussed becoming more involved with the San Mateo County Flood and Sea Level Rise Resiliency District, the agency known as One Shoreline, which looks to promote regional collaboration and alignment in addressing sea-level rise. 

The agency has worked with other jurisdictions, including the city of Burlingame, that has adopted language for sea-level rise overlay zones requiring private developments on the shoreline to be responsible for raising their portion. This effort codified in the city’s zoning code can be something Redwood City should consider in the future, Brennan said.