Friday, November 22nd, saw over two inches of rainfall across San Franciso — the most rainwater SF has seen in a single day since the 100-year storm on New Year’s Eve Day in 2022.
San Francisco is naturally unique in almost uncountable ways. Between its namesake marine slayer and endemic population of blue butterflies, to its exaggerated high tides and gorgeous vistas, this 49-square-mile city is rife with intrinsic wonders.
But its environmental idiosyncrasies also compound certain weather hazards, some of which are compounded by San Francisoc’s antiquated combined sewer system — a relic of sanitation infrastructure of yesteryears and the only one of its kind still used in any major California city. There’s perhaps no more significant nexus of the two hyperlocal quirks than when flash flooding conditions inundate San Francisco.
On Friday, November 22nd, the SF Bay Area’s recent atmospheric bomb cyclone and atmospheric river event peaked, delivering over 2” of rain across the seven-by-seven/ But San Francisco hills and inability to contend with large amounts of sudden water meant an inevitability happened again: many parked cars in Bayview, SoMa, Marina District, and other low-elevation neighborhoods were almost submerged.
In social media posts published by various media outlets, e.g. the San Francisco Chronicle and Mission Local, cars parked in SF’s South of Market district were filmed and pictured mounted by rainwater.
“Three cars were almost submerged under flood waters in the Bayview in San Francisco early Friday evening, near the intersection of Toland Street and Evans Avenue,” reads an Instagram post posted by the San Francisco Chronicle, before mentioning the nearly record-breaking nature of the storm. “San Francisco has already logged its wettest day since New Year’s Eve 2022 when 5.46 inches fell.”
The New Year’s Eve storm nearly two years ago shattered rainfall records across the San Francisco Bay Area. Rapide and intense flash floods caused hours-long traffic delays to and from SFO, house floods in the Mission District, and mudslides in San Francisco. Months after the flood, the San Francisco Public Utilities Commission (SFPUC) released an updated flood risk map, highlighting areas likely susceptible to dangerous floods during once-in-a-century storms, defined as a weather event in San Francisco producing 6 inches or more of rain; the emphasized areas aren’t served by the City’s combined sewer and stormwater system, efficiently meaning all rainfall collected in the area isn’t guided nor mitigate — it just follows a path of least resistance — and some also fall inside historical waterbodies.
Where are these spotlighted areas mostly concentrated? You guessed it: Bayview, Mission District, and South of Market.
Videos of cars (stupidly) driving through fender-high water in these neighborhoods, including the Marina District, were posted on X; a map shared on the platform showed how the city’s elevation dips mean some areas can see almost twice as much collected standing rainwater as the average San Francisco neighborhood during strong storms.
Thankfully, no one was killed inside a vehicle during San Francisco’s flash flooding event Friday; one individual was, unfortunately, found deceased inside a flooded car in Sonoma on Sunday.
As the climate crisis continues to increase the frequency of these otherwise 100-year storms, San Francisco’s flash floods will bring increasingly dangerous flood conditions to vulnerable neighborhoods.
Feature Image: Courtesy of X via [at]PearsonTriton
