Flooding is the most common natural disaster in the United States. Although it is more likely to occur during California’s rainy season from November through April, flooding can occur at any time of the year. Wildfires have changed the landscape and ground vegetation, making some areas more susceptible to mud flows. California has an extensive levee system in place to help protect against flooding. However, these structures can erode, weaken, or overtop, causing devastating results.
Types of floods
Spring Thaw – 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. Coupled with spring storms, this can result in serious flooding.
Levees and Dams – Levees are designed to protect against a certain level of flooding. Levees decay over time, posing a serious maintenance challenge. Levees can overtop or fail during large floods, which can create more damage than if the levee wasn’t there.
Heavy Rains – La Niña weather conditions can cause snow melts, heavy rains, and additional mudslide risk due to vegetation loss from recent wildfires. This excessive rainfall can happen throughout the year.
Flash Floods – Rapid flooding of low-lying areas in a period of less than six hours caused by heavy rainfall. They are the deadliest weather-related occurrence in the United States because they can roll boulders, tear out trees, and destroy buildings and bridges.
Before a flood
- Determine the flood risk in your area. Areas that are low-lying, near rivers, and downstream from dams are more susceptible to flooding. Check with the American Red Cross or the Office of Emergency Services if you are unsure of your risk level.
- Elevate your home’s furnace, water heater, and electric panel if you are prone to flooding.
- Consult with a professional for further information to determine if other damage reduction measures should be taken.
During a flood
- Stay alert. Listen to NOAA Weather Radio, commercial radio, or television for more information if there has been ongoing, heavy rain.
- If you must evacuate, secure your home. If you have time, bring in outdoor furniture. Move essential items to an upper floor. Turn off utilities at the main switches or valves if instructed to do so. Disconnect electrical appliances. Do not touch electrical equipment if you are wet or standing in water.
- If you have to leave your home, do not walk through moving water. Six inches of moving water can make you fall. If you have to walk in water, walk where the water is not moving. Use a stick to check the firmness of the ground in front of you. Do not drive into flooded areas. If floodwaters rise around your car, abandon the car and move to higher ground if you can do so safely. You and the vehicle can be quickly swept away.
Know the warnings
- A Flood Watch means that flooding is possible in your area.
- A Flood Warning means that flooding is occurring or will occur very soon. If you have been advised to evacuate, do so immediately.
- A Flash Flood Watch means that a flash flood is possible. Be prepared to move to higher ground.
- A Flash Flood Warning means that a flash flood is occurring; seek higher ground on foot immediately.