Floods in California

All types of floods can occur in California, though 90% are caused by riverine flooding. Such flooding generally occurs as a result of excessive rainfall, excessive snowmelt, excessive runoff, levee failure or a combination of these sources. Below is a list of flood events that were of significant impact to California

Changed the course of the Los Angeles River from its western outlet into Santa Monica Bay following the course of Ballona Creek to a southern outlet at San Pedro Bay near where it is today.

In January 1850, a major flood devastated the new city of Sacramento; rain from heavy storms saturated the grounds upon which Sacramento was built, and the American and Sacramento rivers crested simultaneously.

Many floods occurred later in the city of Sacramento and other low lying cities along the Sierra born rivers due to hydraulic mining at locations in the foothills, for example Malakoff Diggins in which sludge runoffs purportedly raised the river beds in the valley below, an additional two feet. Hydraulic Gold mining became a hot topic for the time and was eventually stopped by California Lawmakers.

Beginning on December 24, 1861, and lasting for 45 days, the largest flood in California's recorded history occurred, reaching full flood stage in different areas between January 9–12, 1862. The entire Sacramento and San Joaquin valleys were inundated for an extent of 300 miles (480 km), averaging 20 miles (32 km) in breadth. State government was forced to relocate from the capital in Sacramento for 18 months in San Francisco. The rain created an inland sea in Orange County, lasting about three weeks with water standing 4 feet (1.2 m) deep up to 4 miles (6 km) from the river. The Los Angeles basin was flooded from the San Gabriel Mountains to the Palos Verdes Peninsula, at variable depths, excluding the higher lands which became islands until the waters receded. The Los Angeles basin lost 200,000 cattle by way of drowning, as well as homes, ranches, farm crops & vineyards being swept-away.

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