Flooding poses a serious risk to life, property and public health and safety and could cripple the state’s economy. Substantially populated counties with vulnerable populations are in flood-prone areas of southern California, the San Francisco Bay Area, the Delta region and the Central Valley. In addition, many urban and rural areas are not protected by levees and are subject to recurring, seasonal flooding by local rivers or streams.
- In 2000, over 5 million Californians, or approximately 15 percent of the total population, lived in a Flood Insurance Rate Map (FIRM) designated floodplain. Most of this population resides in expanding urban centers located in floodplains where flooding could result in extensive loss of life and billions of dollars in damages.
- The potential direct flood damages in the Sacramento area alone could exceed $25 billion. Some areas of the Central Valley could experience flood depths of twenty feet or more if a levee fails.
You can check your potential for flood risk by your address or zip code by checking "My Hazards"
What types of flooding may occur
California's rainy season usually lasts from November to April, bringing heavy flooding and increased flood risks with it; however, flooding can happen at anytime. A string of large wildfires have dramatically changed the landscape and ground conditions, causing fire-scorched land to become mudflows under heavy rain. Experts say that it might take years for vegetation to return, which will help stabilize these areas. The West Coast also has thousands of miles of levees, which are meant to help protect homes and their land in case of a flood. However, levees can erode, weaken, or overtop when waters rise, often causing catastrophic results.
- Spring Thaw
During the spring, frozen land prevents melting snow or rainfall from seeping into the ground. Each cubic foot of compacted snow contains gallons of water and once the snow melts, it can result in the overflow of streams, rivers, and lakes. Add spring storms to that and the result is often serious spring flooding.
- Heavy Rains
California is at heightened risk for flooding due to heavy rains. The is high risk due to La Niña conditions, which include: snow melts, heavy rains, and additional mudslide risk due to vegetation loss due recent wildfires. This excessive amount of rainfall can happen throughout the year, putting your property at risk.
- Levees & Dams
Levees are designed to protect against a certain level of flooding. However, levees can and do decay over time, making maintenance a serious challenge. Levees can also be overtopped, or even fail during large floods, creating more damage than if the levee wasn’t even there.
- Flash Floods
Flash floods are the #1 weather-related killer in the U.S. since they can roll boulders, tear out trees, and destroy buildings and bridges. A flash flood is a rapid flooding of low-lying areas in less than six hours, which is caused by intense rainfall from a thunderstorm or several thunderstorms. Flash floods can also occur from the collapse of a man-made structure or ice dam.
Familiarize yourself with these terms to help identify a flood hazard:
- Flood Watch
Flooding is possible. Tune in to NOAA Weather Radio, commercial radio, or television for information.
- Flash Flood Watch
Flash flooding is possible. Be prepared to move to higher ground; listen to NOAA Weather Radio, commercial radio, or television for information.
- Flood Warning
Flooding is occurring or will occur soon; if advised to evacuate, do so immediately.
- Flash Flood Warning
A flash flood is occurring; seek higher ground on foot immediately.
Real Time Flood Information
California Data Exchange Center (CDEC)
- installs, maintains, and operates an extensive hydrologic data collection network including automatic snow reporting gages for the Cooperative Snow Surveys Program and precipitation and river stage sensors for flood forecasting. CDEC provides a centralized location to store and process real-time hydrologic information gathered by various cooperators throughout the State. CDEC then disseminates this information to the cooperators, public and private agencies, and news media.
Suggested tips for before, during, and after flooding
The Centers for Disease Control and Prevention (CDC) has specific information on what steps should be followed when returning to your residence or business after a flood. Information is available by clicking on the links below:
- California Department of Water Resources Flood & Safety Topics
- FEMA Flood Information - FEMA information as floods are one of the most common hazards in the United States. Flood effects can be local, impacting a neighborhood or community, or very large, affecting entire river basins and multiple states.
- Ready America - Floods - Provides additional information on flooding which is the nation's most common natural disaster. It's important to be prepared for flooding no matter where you live, but particularly if you are in a low-lying area, near water or downstream from a dam. Even a very small stream or dry creek bed can overflow and create flooding.
- California Hospital Association - Flood Preparedness for hospitals is discussed by the CHA.
For information on protecting or mitigating potential flood damage, please refer to the links below: