Floods in California

All types of floods can occur in California, though 90 percent of them are caused by river flooding in lowland areas. Such flooding generally occurs as a result of excessive rainfall, excessive snowmelt, excessive runoff, levee failure, poor planning or built infrastructure, or a combination of these factors. Below is a list of flood events that were of significant impact to California.

A 2022 study found that Climate change in California, is likely to increase the extremity of water cycle events such as droughts and megafloods, greatly increasing the severity of future floods due to atmospheric rivers. In part this is due to the expectation that the Sierra Nevada mountains, which typically retain water as snow, will no longer be as cold.