It was called the biggest and strongest rainstorm to hit the Bay Area in a quarter century, but last October's "bomb cyclone" event may be just a preview of what climate change will bring to the Bay Area in the coming decades.
The City of San Francisco commissioned a new study from Lawrence Berkeley National Laboratory that looks ahead to the ways that "extreme precipitation" in the coming decades will impact the Bay Area. And it's the first study of its kind to take the unique topography of the local region into account, forecasting impacts based on two-square-mile segments — compared to earlier studies that looked at the singular impacts for the entire region.
The study projects that storms like the one in October will dump 26% to 37% more water on the Bay Area, when they hit, by the end of the century. The study looked at various storm types and atmospheric river combinations to estimate total storm precipitation totals from 2050 and beyond.
"Having this level of detail is a game changer," said SF Public Utilities Commission General Manager Dennis Herrera in a statement. "This groundbreaking data will help us develop tools to allow our port, airport, utilities, and the City as a whole to adapt to our changing climate and increasingly extreme storms. ... In practical terms, we simply can’t build a sewer pipe big enough to handle all of this water. We must think holistically about how we build, what we build, and where we build it.”
"This collaboration is one of the first of its kind to apply the climate modeling expertise at Berkeley Lab to inform local decision-makers,” said Michael Wehner, one of the co-authors of the study, in a statement. “By tailoring our models to the City’s specific questions, we are able to provide more confident answers in the amount of heavy rainfall that can be expected in a future warmer world.”
The study focuses primarily on how these mega-storms may impact urban environments like San Francisco, and it doesn't necessarily answer questions about overall water resources in the coming decades. The jury, scientifically, is still out on that.
As the Chronicle reports, "The precise science is unsettled: Some studies say California will get more rain in the future due to a changing climate, while others suggest it will get less rain." And we've already seen studies that predict there will be warmer temperatures and little overall snowpack in the Sierra as soon as 25 years from now, which will greatly impact how much water is available for residents to consume.
But the study will hopefully aid the city and its departments in developing shoreline adaptation strategies and flood mitigation plans to deal with the specific threats posed by "bomb cyclones" and the like — the kinds of very wet storms that our region hasn't so far been built to withstand.
Related: Study: Sierra Snowpack Could All But Disappear In 25 Years