(KRON) — The recent storms through the Bay Area have caused major flooding in parts of the Bay Area as well as severe damage from saturated soil.
“These nine storms that we just had in the Bay Area, those brought more rain than all the storms we analyzed since 2020,” said Doctor Kris May, CEO and principal at Pathways Climate Institute.
After the atmospheric river that began around Dec. 30, 2022, doused the Bay Area, May said all of the soil’s capacity to soak up water was gone, exacerbating flooding.
But more areas could become vulnerable to this flooding if the groundwater table continues to rise, according to an inland flooding groundwater response study for Alameda, Marin, San Francisco and San Mateo counties conducted by the Pathways Climate Institute and the San Francisco Estuary Institute.
“As the groundwater table rises, the soils below the groundwater surface will become saturated, reducing the ability of rainwater to infiltrate below the ground surface in permeable areas and creating more surface ponding after rain events,” the study stated.
“I think one of the main takeaways is that, with sea level rise, the area at risk is actually much larger than people think it is if you’re only looking at coastal flooding,” May said. “The risk could also come much earlier because some communities could flood from below.”
May said if the Bay Area continues to see wet winters over the next 20 years, areas that have been built on filled in wetlands are at highest risk for severe flooding, including Alameda, Oakland Airport, San Francisco Airport, east Oakland near the Colosseum and San Mateo. She added that many of the highest-risk areas where those that experienced the worst flooding during the recent storms.
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Interactive maps show flooding from emerging groundwater under various sea level rising scenarios. May said especially due to the recent storms, the groundwater table is inching closer to the 12-inch sea level rise. And the typical wettest part of the winter hasn’t even begun.
“If we had another huge storm next week, the flooding will happen so much quicker,” May said. “Groundwater moves so slow; it’s going to take a long time for it to come down to the low-lying areas.”
Not only does a rising groundwater table impact flooding, it also raises the probability of a 6.7-magnitude earthquake in the Bay Area due to liquefaction–when soil becomes so saturated it acts like a liquid along a fault line.
“Imagine shaking a bowl of Jell-O,” May said. The damage from the earthquake will be much more severe.
May added that this also greatly impacts infrastructure updates.
“As we’re designing and building–or rebuilding things, because we have a lot of old infrastructure that needs to be updated–we need to keep in mind that the groundwater table is already 3 to 6 feet higher than we think and design for those conditions, so things have a longer lifespan.”
May said she hopes city planners, local government and elected officials that may help these areas get funding for infrastructure updates take this data into consideration.
“Sea level rise adaptation is important,” May said. “If we don’t consider the rising groundwater and the extreme storms, we’re not solving the problem.”