South San Francisco Zoning Code - Flood Plain / Sea-Level Rise Overlay
In October 2022, the South San Francisco, CA City Council, updated its zoning code to incorporate a Flood Plain/Sea Level Rise (SLR) overlay district intended to “mitigate the impacts of sea level rise, and protect the health, safety, and welfare of residents of [South San Francisco].” The additional purposes of the overlay district are to “limit the potential impact of coastal flooding and erosion patterns on coastal development,” adapt to climate change, create adaptation strategies with a priority on long-term resilience, “establish standards consistent with the San Mateo County Flood and Sea Level Rise Resiliency District,” introduce “flood-proof” construction to South San Francisco, and restore creek ecologies to build resilience.
The overlay district will include all of the areas of South San Francisco within the FEMA flood zone map, all of the areas within South San Francisco’s 100-year flood zone and the 2100 mid-level scenario of 36 inches of sea-level rise, and the jurisdiction of the San Francisco Bay Shoreline Area within a 100-foot “shoreline bend.”
The SLR overlay district includes a variety of new development standards that affect new and “substantial” construction. These standards include new construction requirements and requirements that shoreline infrastructure “with frontage on the San Francisco Bay… have an elevation sufficient to protect against the FEMA 100-year event with 3 feet of sea level rise.” "Building height within the Flood Plain/Sea Level Rise Overlay District will be measured from the Sea Level Rise Base Flood Elevation (SLR-BFE). The SLR-BFE is defined as or three feet above the project site’s Base Flood Elevation on the FEMA FIRM in place at the time the Project application is deemed complete, or 77 inches above sea level.” Additionally, these regulations cover the lowest floor on a building within the overlay. The lowest floor in a building cannot be lower than the sea-level adjusted base flood elevation.
Within the overlay district, there are also stormwater runoff and drainage requirements. Stormwater infrastructure must be designed to function during a 100-year flood event with “three feet of sea level rise.” The infrastructure must “mimic natural watershed processes… that reduce, filter, or slow runoff before entry into the storm drainage system.”
Finally, any building within the overlay district has a mandatory disclosure of hazards. This disclosure requires property owners to share information regarding risk of any hazards affecting the property associated with anticipated sea-level rise or flooding. This disclosure applies generally as well as specific hazards to the property.
The SLR overlay district requires a bay access buffer extending 100 feet from the San Francisco Bay Shoreline. The buffer is intended to “accommodate and maintain built and natural shoreline infrastructure for sea level rise protection, environmental enhancement, and public access trails.” The buffer requires building encroachments, shoreline access, and trails.
Before issuing a building permit within the SLR overlay district, all new “construction, repairs, or alterations,” must be accompanied by a site clearance. Rehabilitation of a building in the SLR overlay district must have a current elevation certificate. Any addition to a building in the SLR overlay district must have a current elevation, a physical survey that “accurately depicts current improvements on the property, and documents the type of flood… and depth based on available resources.” Any new construction bigger than 50% of the building’s appraised value must be accompanied by two topographic surveys of the property, type of flood and depth of flooding, proposed grades, proposed structures/improvements, finished floor elevations of all structures, the elevation of the lowest floor, and a landscape plan.
Structures prohibited within the SLR overlay district include emergency shelters, fire stations, schools, and healthcare facilities.
Publication Date: October 2022
Related Organizations:
- City of South San Francisco, California
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- Laws
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