After a month of devastating wildfires, the North Bay must now keep an eye out for sudden flooding. A storm is expected to wallop the Bay Area today and Thursday bringing with it increased danger of flash floods, mudslides, and “debris flow” in fire-affected areas.
The National Weather Service (NWS), a meteorological arm of the National Oceanic and Atmospheric Administration, has issued a Wednesday flash flood watch for Santa Rosa and other Northern California cities near recent burn zones:
Flash Flood Watch for a portion of northern California, including the North Bay Interior Valleys and North Bay Mountains.
Impacted areas include the recent Atlas, Tubbs, Nuns, and Pocket burn scars, as well as the Fountaingrove neighborhood in northeast Santa Rosa.
[...] Forecast rain amounts will range from one to two inches for the North Bay Valleys and two to three inches for the North Bay Mountains with locally higher amounts possible, particularly for southwest-facing slopes. Rainfall rates are expected to reach or exceed half-inch per hour.
The flash flood watch will go into effect from 4 p.m. Wednesday to 3 a.m. Thursday. The NWS forecast calls for rain all day in Santa Rosa and San Francisco areas, with a high chance of rain continuing into Thursday.
A flash flood watch means “conditions are favorable for flooding.” It does not mean flooding will definitely occur, “but it is possible.”
Recently burned areas are particularly susceptible to floods and related dangers because the ground may not be able to absorb rain as quickly and efficiently as usual.
Landslides and debris flows—which Geology.com defines as “a moving mass of loose mud, sand, soil, rock, water and air that travels down a slope”—may also develop in and around fire-ravaged areas.
The Department of Homeland Security’s (DHS) flood safety site warns that when a flood watch is in effect those in the area should tune in to television and radio to get the latest warnings and identify nearby higher ground accessible on foot. Planning an evacuation route is also a sound idea.
DHS also says that now is a good time to “build or restock your emergency preparedness kit” and to “include a flashlight, batteries, cash, and first aid supplies,” if possible.