It infiltrates sewer pipes, which can cause backups and burden treatment plants with excess water.

Even before it comes to the surface, rising groundwater casts a net of damage. The rise in groundwater contributes to flooding in low-lying communities in the nine counties that ring San Francisco Bay. Kristina Hill, a professor at the University of California, Berkeley, who studies urban design and flooding, has been instrumental in shedding light on this neglected aspect of flood risk in the Bay Area.Īs bay levels rise, so do groundwater levels along one of the most developed shorelines on the West Coast. What is less obvious is that groundwater levels are rising as well, adding another variable to the region’s equation of increasing flood risk. That relationship between rising ocean levels and rising bay levels is well known. As sea levels rise, so do the waters in the bay, which connects to the Pacific Ocean through the Golden Gate. Worse in the winter, king tides are seen as a climate change preview, a glimpse of what average water levels could be decades in the future.īut king tides are only part of the region’s flood story. The flooding on this day is the work of king tides, the biggest tides of the year, which lifted water levels in San Francisco Bay to annual highs in the first week of February. “Those of those who live in this area of southern Marin get our feet wet with some regularity,” Kate Sears, a Marin County supervisor, told Circle of Blue, noting that the Manzanita area floods more than 30 times a year, even on blue-sky days when the tides are high. Nearby, the Mill Valley-Sausalito multi-use trail is partially submerged, a ribbon of asphalt peaking above mirrored waters. At an adjacent park-and-ride, public buses plow through standing water to pick up passengers. In Manzanita, the northbound on-ramp for Highway 101, the main artery through this county just north of San Francisco, is partially covered with a half foot of water.

MARIN COUNTY, California - It’s a calm, sunny day at the start of a rainless February in the San Francisco Bay Area, and streets are flooded. A king tide on February 7, 2020, pushed the bay to one of its highest levels of the year. A runner passes rising waters along the Mill Valley-Sausalito Path, a multi-use trail in Marin County, California that skirts an inlet of San Francisco Bay.

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