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SFPUC presents draft 100‑year storm flood‑risk map and outlines disclosure process
Summary
Commission staff presented a draft citywide 100‑year storm inundation map that would identify parcels at risk of deep, contiguous flooding, notify affected owners, allow parcel appeals and support a future City ordinance requiring disclosure at point of sale.
The San Francisco Public Utilities Commission on Feb. 13 unveiled a draft 100‑year storm flood‑risk information map intended to tell property owners and prospective buyers whether a parcel is subject to deep, contiguous flooding in an event with a 1% annual probability.
Stephanie Harrison, project manager, said the draft map isolates deep and contiguous flooding (defined as more than 6 inches and larger than half a block in the right of way), incorporates sea‑level rise assumptions and uses hydrologic/hydraulic modeling to identify impacted parcels. Staff estimate the draft map covers a bit more than 2,000 parcels (about 1–2% of city parcels and properties). Harrison recommended a process to notify owners in March, provide parcel‑level technical information (e.g., model depth and extent, elevation), and offer an appeals process before final adoption.
Commissioners asked whether inclusion in the map would affect flood‑insurance availability or premiums. Harrison said federally backed National Flood Insurance Program policies are available citywide and that most parcels on the draft map lie outside FEMA‑designated coastal floodplains, so premiums for mapped parcels can be substantially lower than coastal FEMA floodplain rates. Harrison gave sample 2017 NFIP premium figures: contents‑only renter policies can start around $40 annually; combined structure and contents with a basement could start at about $127 annually, depending on property value.
On climate change and storm statistics, staff said sea level rise projections are better characterized than precipitation changes at a micro scale; the commission is working with Lawrence Berkeley National Laboratory to refine extreme‑precipitation understanding but told commissioners there is not yet a scientific consensus to quantitatively change the 100‑year statistic used in the mapping.
Staff said the 100‑year map’s primary purpose is information and disclosure; a smaller 25‑year storm map is planned for future regulatory or grant prioritization and the 5‑year design standard remains the focus for capital investments. If the commission adopts a final map, staff would tie it to a disclosure ordinance and to periodic reviews and appeals processes.
Next steps: staff will mail notifications to affected property owners, conduct stakeholder outreach (including real‑estate industry groups), post draft maps online and schedule public hearings and an adoption hearing later in the year.
