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-  California Water Science Center 

#           California's History of Large Storms & Floods      

      By California Water Science Center

## Major Storms and Floods in California History

### California's largest storms, such as the atmospheric river events, unleash torrential rain and intense winds, posing significant challenges to infrastructure and triggering widespread flooding.

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California's largest storms, such as the atmospheric river events happening now, unleash torrential rain and intense winds, posing significant challenges to infrastructure and triggering widespread flooding.*Photos in carousal above by Travis Apo, hydrologist and Anthony Smith, physical scientist*

### **Great Flood of 1861-1862**

The Great Storm of 1861-1862, often referred to as the Great Flood of 1862, was a series of intense storms that battered California for several weeks. The event occurred during the winter months, particularly between December 1861 and January 1862 when the state experienced an exceptionally rainy season, causing widespread flooding that affected nearly the entire region. Rivers overflowed, levees were breached, and vast areas were submerged under water. The Central Valley turned into an immense lake, disrupting transportation and isolating communities. The economic impact was severe, with substantial losses in agriculture and infrastructure. This historic flood remains unparalleled in its magnitude and remains a benchmark for California's vulnerability to extreme weather events.

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The magnitude of the flooding was unprecedented, affecting both northern and southern California. Rivers swelled, and extensive rainfall saturated the soil, leading to mudslides and inundating low-lying areas. Sacramento, the state capital, experienced severe flooding, with water levels reaching the second floor of some buildings. The city was essentially transformed into a temporary inland sea.

The economic impact was substantial, as infrastructure, farmland, and transportation systems were heavily damaged or destroyed. The cattle industry suffered significant losses, and the state's economy was severely affected. This historic flood is considered one of the most extreme weather events in California's recorded history. The Great Storm of 1861-1862 underscored the vulnerability of the region to intense winter storms and contributed to subsequent efforts to implement flood control measures and improve water management in the state.

### **St. Francis Dam Disaster of 1928**

Following storms, the St. Francis Dam disaster in 1928 resulted in catastrophic flooding. The dam, situated near Los Angeles, collapsed, releasing an enormous volume of water downstream. The floodwaters surged through the canyon, sweeping away everything in their path. Several towns and communities in the path of the flood were devastated, including the town of Santa Paula. The flood eventually reached the Pacific Ocean, approximately 54 miles away.

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The disaster resulted in the loss of at least 431 lives, making it one of the deadliest engineering failures in U.S. history. The cause of the dam failure was later attributed to geologic and design flaws, as well as poor construction practices. The St. Francis Dam Disaster led to increased scrutiny and reforms in dam construction and engineering practices to prevent similar tragedies in the future.

### **Christmas Flood of 1964**

The storm began around December 19, 1964, and continued through the Christmas holiday period, peaking on December 22-23., where a series of storms, fueled by an atmospheric river, contributed to the heavy and sustained rainfall. It led to what is now known as the Christmas Flood. Rivers across the state swelled to record levels, breaching levees and inundating communities. Northern California was particularly affected, with widespread damage to homes, infrastructure, and agricultural lands. The disaster prompted increased efforts in flood control and infrastructure development, with the subsequent creation of the California State Reclamation Board to address flood-related issues.

### **New Year's Flood 1997**

In early 1997, heavy rainfall and warm temperatures triggered significant snowmelt, causing widespread flooding across Northern California. The Russian River and other waterways overflowed their banks, inundating communities and triggering evacuations. The flood resulted in several casualties and extensive property damage. The disaster prompted improvements in forecasting and emergency response systems, as well as increased investment in floodplain management and levee improvements to mitigate the impact of future floods.

### **Oroville Dam Crisis 2017**

Although not a traditional flood event, the Oroville Dam crisis in 2017 posed a severe threat of catastrophic flooding. The dam's main spillway suffered extensive damage, and concerns about its structural integrity forced the evacuation of nearly 200,000 residents downstream. Emergency repairs were initiated to prevent a potential breach. This crisis underscored the importance of maintaining and upgrading critical infrastructure and prompted a reevaluation of dam safety protocols across the state.

### Geospatial Information

### Contacts

#### Mark R Dickman

##### Associate Director for Data

California Water Science Center

mdickman@usgs.gov

916-666-9951

#### Louis A Caldwell

##### Deputy Associate Director for Data

California Water Science Center

lacald@usgs.gov

619-988-5805

#### Shipra Shukla

##### Public Affairs Specialist

Communications and Publishing

sshukla@usgs.gov

916-532-3024