This same phenomenon has been occurring in the backyards of many Bay Area residents. Redwood Shores, a region of Redwood City built largely on reclaimed wetlands and landfill, is particularly susceptible to sinkage.
“I live in Redwood Shores, and it’s really at risk to all this sort of stuff because it’s level with the ocean and was built on the marshes,” said Zoe Hardman, a Carlmont freshman.
However, the change isn’t always noticeable. Since sinkage happens at just millimeters every year, it often goes unrecognized.
“At first, you don’t see it, because it’s your whole house, your whole driveway,” said Christine Smith*, a longtime resident of Redwood Shores. “But over time, you can see the slope.”
In fact, subsidence is most obvious during floods, which the city is particularly prone to. First Street, which specializes in climate risk financial marketing, finds that 98.4% of Redwood Shores properties are at risk of flooding. Additionally, the Water Education Foundation notes that the city holds the greatest risk for severe flooding in California.
In December 2022, Northern California experienced significant rain events that led to flooding in Smith’s home.
“The soil, which is basically landfill, was 100% soaked. And your house is on a foundation that is 100% soaked,” Smith said. “Your house is sinking, literally sinking.”
Not only did this incur expensive reparation fees for homeowners, but the excess rainwater also led to issues with drainage. Sewage and garbage seeped into many roadways.
“There were days when I could smell the sewage water in my street,” Smith said.
Many are also concerned about the future of Redwood Shores if the sinking is not properly addressed.
“People would have to adapt and figure out how to protect their stuff depending on how high the flooding is,” Hardman said.