DATE: January and March 1995
ESTIMATED COST: $4 billion*
WHAT HAPPENED: "El Niño" conditions brought strong storms, producing floods that led to federal disaster declarations in 57 of the state's 58 counties. Along the Russian River, the accumulation of vegetation and debris reduced the stream's capacity, raising water levels to record highs. Heavy development in floodplains elsewhere led to bridge collapses and flooded downtowns, including San Jose's. In the Sacramento River Valley, a particularly hard-hit area, storm drainage system failures were to blame — and the region remains at risk for a Katrina-like event.
*All costs estimated in 2009 dollars.