Elevation Certificates in Redwood City, CA

In Redwood City, flood zone status is largely a levee question. OneShoreline, San Mateo County's flood and sea level rise district, describes Redwood Shores as protected by a levee system, with more than three miles of it raised in 2010 to meet FEMA requirements. In April 2020, FEMA notified the city that the levee system had to be modified to remain eligible for accreditation, or about 4,700 households would face mandatory flood insurance. The city is leading the Redwood Shores Sea Level Rise Protection Project in response, with OneShoreline on its technical advisory committee. The county's 2018 sea level rise vulnerability assessment, cited by OneShoreline, found that a 100-year flood with 3.3 feet of sea level rise would inundate Redwood Shores entirely. Redwood City was also among the agencies that appealed FEMA's San Francisco Bay coastal analysis and lost.

The bayfront flatlands have a second, more frequent problem. OneShoreline reports that businesses and mobile home parks along the Bayfront Canal and Atherton Channel, which drain Redwood City, Menlo Park, Atherton, Woodside, and nearby unincorporated areas, flooded more than 40 times over 70 years because high tides kept stormwater from draining to the bay. The Bayfront Canal and Atherton Channel project, completed in December 2023, now diverts excess water through two parallel underground culverts into managed ponds at the Ravenswood Pond Complex. That project addresses local drainage. It does not by itself change a FEMA flood zone, so owners should still check the effective FIRM for their parcel.

For a Redwood City flood elevation certificate we tie a benchmark on the FIRM's vertical datum with GNSS, then measure the lowest adjacent grade, lowest floor, garage, crawlspace, and machinery and utilities with a Trimble S3 total station. We take the FEMA-required photographs and deliver a signed FEMA Form FF-206-FY-22-152. In levee-protected areas an existing certificate gives you a baseline if the map designation ever changes. For structures that sit at or above the Base Flood Elevation but are shown in the SFHA, we can prepare a letter of map amendment and file through eLOMA when eligible. Redwood City work is scheduled as a mobilization from Lotus. See our elevation certificate service and the Foster City, San Mateo, and Palo Alto pages.