100-Year Storm Flood Risk Map
Adopted by SFPUC Commission on September 25, 2018
This map is intended as an informational tool to illustrate the potential for flooding across San Francisco in a 100-year storm. There is a 1% chance of a 100-year storm occurring in a given year. The map shows parcels that are highly likely to experience "deep and contiguous" flooding during a 100-year storm. "Deep and contiguous flooding" means flooding at least 6-inches deep spanning an area at least the size of half an average City block. This map does not provide the exact depth of flooding at a given location. It also does not show areas in the City that may experience shallower and/or more localized flooding in a 100-year storm, or areas of the City that may flood in storms larger than a 100-year storm.
The map was created using a hydrologic and hydraulic computer model, utilizing a digital elevation model created from 2010 LiDAR data and information on existing City infrastructure. The model's calculations take into account projected sea level rise and storm surge causing elevated bay levels. The map is based on model outputs and do not account for future conditions such as new construction, infrastructure upgrades, or other changes that may affect flooding. Although care was taken to capture relevant topographic features and structures in the City, site specific conditions may not be fully represented. The map will be updated as needed to reflect changes in the City's infrastructure and urban land uses.
The hatched areas on the map are not served by
the SFPUC's combined sewer and stormwater collection system and were not part
of the SFPUC's flood analysis. This map does not provide flood risk information
for those areas.
Finally, this map shows flood risk from storm runoff only. It does not consider flood risk in San Francisco from other causes such as inundation from the San Francisco Bay or Pacific Ocean. For information on flood risk from other causes, please see the Sea Level Rise Vulnerability Zone Map (http://onesanfrancisco.org/sea-level-rise-guidance) and the FEMA Preliminary Flood Insurance Rate Maps (http://sfgsa.org/san-francisco-floodplain-management-program).