We don’t usually think of San Francisco as flood prone, or as a place impacted by severe storms. However, recent winter rains have caused floods, landslides, uprooted trees, and downed or broken utility lines in some neighborhoods. When rain hits paved or “non-permeable” surfaces like the streets, buildings and sidewalks that cover the City, all of the water runs off into our collection system. One reason flooding occurs is because some sewers are too small to handle large volumes of water and can’t transport runoff quickly enough. Flooding also happens where homes are below grade and in locations where the terrain is prone to settling or "subsidence."
A number of these low-lying areas in the City are more prone to flooding in intense rainstorms. In 2005, the SFPUC launched a 5-Year Wastewater Capital Improvement Program to help improve the flow of wastewater in these areas. Building on this, the 30-year master plan will look at the entire system to improve conditions through the City during heavy rains.
