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, tsunami, 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.
Background and climatology Every county in California has experienced a flood, which is mostly likely to be caused by an atmospheric river, which is a narrow corridor of moisture in the air that travels a long distance to produce heavy rainfall. , the state of California spends more than US$2.8 billion annually on maintaining or building flood control projects.
Events Pre–1900 Geologic evidence indicates that "megafloods" occurred in the California region in the following years A.D.: 212, 440, 603, 1029, c. 1300, 1418, 1605, and 1750. Prior to European settlement, these early floods predominantly affected the indigenous peoples of California.
1605 – A large flood occurred due to an unusually powerful atmospheric river. This was potentially the largest flooding event in the state of the prior 2,000 years. 1825 – This flood 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. January 1850 – A major flood devastated the then new city of Sacramento; rain from heavy storms saturated the ground upon which Sacramento was built, and the American and Sacramento rivers crested simultaneously. October 2, 1858 – A hurricane near San Diego washed ships ashore. December 24, 1861 – February 1862 – The largest flood in California's history occurred, lasting for 45 days, reaching full flood stage in different areas between January 9–12, 1862. The entire Sacramento and San Joaquin valleys were inundated for , averaging in breadth. State government was forced to relocate from the capital in Sacramento for 18 months to San Francisco. The rain created an inland sea in Orange County, lasting about three weeks with water standing deep up to 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 and vineyards being swept-away.
1900–1949
1909 – The storm extended from Fort Ross along the Sacramento River up to the Feather River basin. One small town along the flood path (La Porte) was inundated with over the course of 20 days. The flood episodes of 1907 and 1909 in California resulted in an overhaul of planned statewide flood control designs. March 1928 – The recently constructed St. Francis Dam collapsed 40 miles northwest of downtown Los Angeles due to a combination of faulty design and a defective soil foundation. The flooding downstream from the dam killed at least 431 people, making it the third-greatest loss of life events in California. Late December 1933 – The Crescenta Valley flooding occurred after of rain fell in the communities of La Crescenta, La Cañada and Montrose just north of Los Angeles. On New Year's Eve, more rain fell. The result was a flood of mud and water that began around midnight, destroying more than 400 homes in the area. This was commemorated in Woody Guthrie's song "Los Angeles New Year's Flood". As a result of this flood, the Army Corps of Engineers and the County of Los Angeles built a flood control system of catch basins and concrete storm drains to prevent a repeat of the disaster. February 4–7, 1937 – A storm resulted in the highest four-day rainfall totals at several stations in the Santa Ana River basin. The Riverside North station had over of rain in that four days, which equaled a 450-year event. Other stations also received high amounts of rain within those four days. December 1937 – The storm of December 1937 was a high-elevation event in the northeast corner of the state. February–March 1938 – Flood in Los Angeles was caused by two Pacific storms that swept across the Los Angeles Basin in and generated almost one year's worth of precipitation in just a few days. Between 113–115 people were killed by the flooding. The Los Angeles, San Gabriel, and Santa Ana Rivers burst their banks, inundating much of the coastal plain, the San Fernando and San Gabriel Valleys, and the Inland Empire. Flood control structures spared parts of Los Angeles County from destruction, while Orange and Riverside Counties experienced more damage. The flood of 1938 is considered a 50-year flood. It caused $78 million of damage ($ in dollars), making it one of the costliest natural disasters in Los Angeles' history. In response to the floods, the U.S. Army Corps of Engineers and other agencies began to channelize local streams in concrete, and built many new flood control dams and debris basins. These works have been instrumental in protecting Southern California from subsequent flooding events, such as in 1969 and 2005, which both had a larger volume than the 1938 flood. September 25, 1939 – A tropical storm known as El Cordonazo, or The Lash of St. Francis, made landfall near Long Beach with sustained winds of 50 mph (85 km/h), which as of 2025 is the most recent tropical storm landfall in California. The storm killed 45 people across southern California, and another 48 people at sea, with residents caught unprepared. Rains related to the storm reached at Mount Wilson. Floodwaters deep inundated the eastern Coachella Valley. Damage reached $2 million.
1950s November 1950 – a statewide disaster was declared November 21 when floods caused 9 deaths and $32 million in damage. December 1955 – The storm affected the central Sierra Nevada mountains and South Bay areas. The Eel River on the North Coast saw the greatest flow of record to that time while Central Valley rivers saw near-record flows. A statewide disaster was declared, with the storm resulting in 74 deaths and $200 million in economic losses. The heaviest 24-hour rainfall was recorded on December 20, when fell in Shasta County. The storm's toll on Sutter County was severe. At 12:04 a.m. on December 24, 1955, a levee on the west bank of the Feather River, at Shanghai Bend, collapsed and a wall of water 21 feet high entered the county, flooding 90 percent of Yuba City and the farmlands in the southern Yuba City basin. Some 600 people were rescued by helicopter and 37 people drowned.County of Sutter, Office of Emergency Management.
1960s October 1962 – The atmospheric river associated with the Columbus Day storm produced flooding and mudslides, particularly in the San Francisco Bay Area. Oakland set an all time calendar day record with of rain on the 13th, as did Sacramento with . More than of rainfall were recorded in the Bay area.J. L. Baldwin, Weekly Weather and Crop Bulletin. U.S. Department of Commerce, p. 1. Heavy rain forced Game 6 of the 1962 World Series at San Francisco's Candlestick Park to be postponed from its originally scheduled date of October 11 to Monday, October 15. March 1964 – A powerful earthquake in Alaska produced a tsunami, devastating several North Coast towns and resulting in 14 deaths and an economic loss of $14 million in Del Norte County alone. December 19–24, 1964 – Flooding along the North Coast were the result of six days of heavy rainfall. Every major stream in the North Coast produced new high values of extreme peak flows. 34 California counties were declared disaster areas.
1970s September 10, 1976 – The remnants of Hurricane Kathleen produced of rainfall along the southern slopes of Mount San Gorgonio, which marked the highest known precipitation related to an Atlantic or Pacific hurricane in the state. Flooding inundated the Coachella and Imperial Valleys, with six people killed in Ocotillo, after 70% of the town was buried in mud. The floods also washed out portions of roads, including I-8. Damage in the state was estimated at over $120 million. August 15–17, 1977 – Former Hurricane Doreen dissipated near San Clemente Island, after bringing a plume of moisture that spread across southern California. The highest rainfall was along Mt. San Jacinto. The storm killed four people and caused $25 million in damage, with hundreds of houses flooded.
1980s January 3–5, 1982 – Heavy rainfall in the San Francisco Bay region on January 3–5 triggered floods across the state. The floods caused thousands of debris flows from Santa Cruz Country to Contra Costa and Sonoma Counties, as well as flooding along the San Lorenzo River, Soquel Creek, and Aptos Creek in Santa Cruz County. Floods along creeks in Marin County added significant amounts of sediment to Tomales Bay. The landslides caused at least $66 million in damage. Landslides caused 25 of the 33 storm-caused deaths. Total estimated storm-related losses were $280 million. February 1986 – On February 11, 1986, a vigorous low pressure system drifted east out of the Pacific, creating a Pineapple Express that lasted through February 24 unleashing unprecedented amounts of rain on northern California and western Nevada. The nine-day storm over California constituted half of the average annual rainfall for the year. Record flooding occurred in three streams that drain to the southern part of the San Francisco Bay area. Extensive flooding occurred in the Napa and Russian rivers. Napa, north of San Francisco, recorded its worst flood to this timeNapa River flood of 1986. while nearby Calistoga recorded of rain in 10 days, creating a once-in-a-thousand-year rainfall event. Records for 24-hour rain events were reported in the Central Valley and in the Sierra. Thousand-year rainfalls were recorded in the Sierras. The heaviest 24-hour rainfall ever recorded in the Central Valley at occurred on February 17 at Four Trees in the Feather River basin. In Sacramento, nearly of rain fell in an 11-day period. System breaks in the Sacramento River basin included disastrous levee breaks in the Olivehurst and Linda area on the Feather River. Linda, about north of Sacramento, was devastated after the levee broke on the Yuba River's south fork, forcing thousands of residents to evacuate. In the San Joaquin River basin and the Delta, levee breaks along the Mokelumne River caused flooding in the community of Thornton and the inundation of four Delta islands. Lake Tahoe rose as a result of high inflow. The California flood resulted in 13 deaths, 50,000 people evacuated and over $400 million in property damage. 3000 residents of Linda joined in a class action lawsuit Paterno v. State of California, which eventually reached the California Supreme Court in 2004. The California high court affirmed the District Court of Appeal's decision that said California was liable for millions of dollars in damages.
1990s January and March 1995 – Over 100 stations recorded their greatest 1-day rainfalls in that station's history. The major brunt of the January storms hit the Sacramento River Basin and resulted in small stream flooding primarily due to storm drainage system failures, though flooding affected nearly every part of the state. The Salinas River exceeded its previous measured record crest by more than four feet, which was within a foot or two of the reputed crest of the legendary 1862 flood. The Napa River set a new peak record, and the Russian and Pajaro rivers approached their record peaks. 28 people were killed and the flood cost $1.8 billion. The flooding also affected Southern California..