Department of Emergency Management

• Spring weather can intensify the chances of flooding. Knowing the conditions of where you are, and where you're going, can help you assess the possibility of a flood. Look out for:

  • heavy rainfall

  • high ocean tides

• Avoid building in a floodplain unless you elevate and reinforce your home. 

• Elevate the furnace, water heater, and electric panel in your home if you live in an area that has a high flood risk. 

• If feasible, construct barriers to stop floodwater from entering the building and seal walls in basements with waterproofing compounds. 

• Clear leaves and debris from street gutters and storm drain grates along your street to allow water to drain out of your neighborhood. 

• Check or build an emergency kit. Keep flashlights, extra batteries and extra blankets handy, as well as a can opener, medicine, first aid supplies and a fire extinguisher. Also, stock up on non-perishable foods such as dry cereal, nuts and protein bars. Try to stockpile at least one gallon of water per person a day for three days. Ready.gov has a lot of emergency preparedness information in multiple languages, including tips on creating low-cost emergency kits. It can be very stressful to sit through a flood in the dark. Aside from comfort, you’ll need light to find your way during an emergency evacuation at night. Headlamps are an excellent emergency lighting option. They are worn on the head, so your hands are freed up for other tasks. Candlelight is not recommended during a flood because of the risk of natural gas leaks. 

• Sign up for SMC Alert – if we can’t reach you, we can’t alert you! 

• Sign up for San Mateo County social media for time sensitive updates (links at the bottom of the page).

• Prepare an evacuation plan: 

  • Under what circumstances will you evacuate? The sooner you leave, the better your chances are of escaping the flood. However, many people are reluctant to leave their homes. Wishful thinking may lead them to believe, “This could never happen to us,” or “It won’t be that bad.” It is challenging to reason during a disaster. So, make a plan before a flood watch or warning takes place. Learning about the categories of alerts will help you make this decision. 

  • Where will you go? Hopefully, you have friends or family who live outside of the storm/flood area. Ask them if you could come to should disaster strike. You could consider going to a hotel until the flood passes. You’ll need to set aside money to pay for the hotel bill. However, hotels often are fully booked during flood disasters. In these situations, churches, community groups, and even locals could open their doors to flood survivors. But what if flooding makes it impossible to leave the area? You might need to evacuate to a storm shelter. These may be opened at area school gyms or other facilities where you can get a meal, rest some (cots are usually available), and maybe even charge your phone. Not super comfortable, but better than nothing to help for a short time. It’s much better to stay with family or friends if that option is available. How will you get there? You’ll need to use your emergency radio to check road conditions to see whether it is safe to evacuate by vehicle. This is why it is recommended to leave before flooding begins as roads will be less crowded with others who are also trying to leave the area. 

• What to do if you’re stuck at home during flooding? One of the biggest storm mistakes is to flee to an attic space. Not realizing how quickly flood water can rise, they end up trapped inside their attic and drown there. Don’t go into your attic if you ever find yourself in a flood disaster. You’d be better off on the roof, where you can signal for help. Consider getting an emergency rooftop hatch for your attic. This way you can safely go to your attic during a flood. If the water rises to this level, you can safely escape through the rooftop hatch. 

• Know the difference between National Weather Service terminology “Advisory,” “Watch,” and “Warning.” 

• Flood Advisory: Be Aware! This is the lowest level of alert. It is issued when flooding might happen but isn’t likely to cause a flood warning. 

• Flood Watch: Be Prepared! A flood watch is issued when conditions are favorable for flooding. 

• Flood Warning: Take Action! A flood warning is only issued once a flood is imminent or may already be happening somewhere in the area. 

• IF a Flood “Warning” is issued: 

• Find shelter right away. 

• Do not walk, swim, or drive through flood waters. Turn Around, Don’t Drown! 

• Remember, only six inches of moving water can knock a person down, and one foot of moving water can sweep your vehicle away. 

• Stay off bridges over fast moving water. 

• Depending on the type of flooding: 

• Evacuate if told to do so. 

• Move to higher ground or a higher floor. 

• Stay where you are. 

• Acquire sandbags if your property is prone to flooding. When filled and stacked correctly, sandbags can redirect a low flow of coursing water away from your home, garage, or garden. Various local agencies offer a limited number of free and filled sandbags. Some offer free bags and sand and require you to fill them yourself. County residents in unincorporated areas may pick up pre-filled sandbags (limit 15) free of charge. Find out where to pick up sandbags, both in unincorporated areas and cities at the link earlier in this bullet item. Some agencies may require an ID to pick up sandbags. Contact your public works or road maintenance department for specific information. You can reach San Mateo County Public Works at (650) 363-4103. 

• Know your zone and make an evacuation plan. Public safety agencies throughout San Mateo County use Genasys (formerly known as Zonehaven) to communicate areas that are being evacuated due to flooding or other emergencies. Areas of the county are assigned a specific short code – a zone. All residents can enter an address to find their zone number. These zones numbers will be used to communicate via emergency alerts, County social media platforms and the news media in the even of evacuation orders or other emergencies. Download the Genasys app here.  

• Clear out rain gutters and downspouts. Turn off automatic garden watering systems. 

• Consider preparing an emergency toilet as you may be unable to use your regular toilet should there be a flood. The excess water in the sewage system may cause backups to occur if you try to flush. A garbage bag lining a bucket works as an emergency toilet. Store waste outside in your back yard (if you have one) until the emergency passes.  

• If the power goes out, never heat your home with a camp stove, oven, or charcoal-burning device. 

• If you live in a multi-family building, have a plan for how to evacuate and where to meet your loved ones. Learn your building’s layout and evacuation plan. Most buildings post an evacuation plan in common areas that lead you to safety. Get to know multiple escape routes in case the closest exit is blocked in an emergency. 

• Keep whistles, flares, and neon paint to signal rescue workers. 

• Learn about lightning safety.

• Call 9-1-1 only in emergencies. An emergency is any serious medical problem, any type of fire and any life-threatening situation or to report crimes in progress. 

• Stay put: The water's depth could change at any moment. If you cannot cross dry land, don't try to wade, stay put or turn around! Even a few inches of flood water can knock an adult off their feet and carry them downstream.

• Don't drive: Water as low as 6 inches can splash your car's air intake and stall it. A foot of water can float your car or truck and carry it away. If there's a lot of water on the road, especially if it's rising, it's best to avoid driving through.

• Get to higher ground: Try to traverse dry ground and get to a higher point, like a ridge or viewpoint, where water cannot reach.

• Be aware that flash flooding can occur. If there is any possibility of a flash flood, move immediately to higher ground. Do not wait for instructions to move. 

• Be aware of streams, drainage channels, canyons, and other areas known to flood suddenly. Flash floods can occur in these areas with or without typical warnings such as rain clouds or heavy rain. 

• Evacuate immediately if told to evacuate. Never drive around barricades. Local responders use them to safely direct traffic out of flooded areas. 

• Contact your healthcare provider if you are sick and need medical attention. Wait for further care instructions and shelter in place, if possible. If you are experiencing a medical emergency, call 9-1-1. 

• Assume tap water may be contaminated. Don’t drink it unless you’ve taken steps to purify it. 

• Listen to KCBS 740 AM, NOAA Weather Radio, KCSM 91.1 FM, KPDO 89.3 FM (Pescadero), KHMB 100.9 FM (Half Moon Bay), and of course, subscribe to San Mateo County's local alerting system for current emergency information and instructions regarding flooding. 

• Check road conditions before attempting to drive. 5-1-1 is the phone and web source for Bay Area traffic, transit, carpool, vanpool and bicycling information. It’s FREE and available whenever you need it – 24 hours a day, 7 days a week – from anywhere in the nine-county Bay Area. Call 5-1-1 or visit 511.org 

• Call 2-1-1 for storm information including information about temporary shelters, if opened. 

• Do not walk, swim, or drive through flood waters. Turn Around. Don’t Drown! 

• Stay off bridges over fast-moving water. Fast moving water can wash bridges away without warning. 

• Stay inside your car if it is trapped in rapidly moving water. Get on the roof if water is rising inside the car. 

• Get to the highest level if trapped in a building. Only get on the roof if necessary and once there signal for help. Do not climb into a closed attic to avoid getting trapped by rising flood water. 

• If you must prepare to evacuate, you should do the following: (1) Secure your home. If you have time, bring in outdoor furniture. Move essential items to an upper floor. (2) 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 spot downed trees: If the branches are entangled in power lines, stay at least 25 feet away and call 9-1-1-immediately. Then call PG&E at (800) 743-5000. If you live in the unincorporated areas of San Mateo County, call the County’s Department of Public Works at (650) 363-4103. If you live in a city, contact your local public works or road department. 

• Visit the FEMA website for flood cleanup information here. 

• Get information on how to deal with mold here.  

• Find information on reentering a flooded home here. 

• Pay attention to official information and instructions. Return home only when officials say it is safe. 

• Stay away from damaged areas unless your assistance has been specifically requested by police, fire, or other relief organization. 

• Avoid moving water. Emergency workers will be assisting people in flooded areas. You can help them by staying off the roads and out of the way. Avoid driving except in emergencies. 

• Wear heavy work gloves, protective clothing and boots during clean up and use appropriate face coverings or masks if cleaning mold or other debris. 

• People with asthma and other lung conditions and/or immune suppression should not enter buildings with indoor water leaks or mold growth that can be seen or smelled. Children should not take part in disaster cleanup work. 

• Be aware that snakes and other animals may be in your house. 

• Be aware of the risk of electrocution. Do not touch electrical equipment if it is wet or if you are standing in water. Turn off the electricity to prevent electric shock if it is safe to do so. 

• Avoid wading in floodwater, which can be contaminated and contain dangerous debris. Underground or downed power lines can also electrically charge the water.  

• Use a generator or other gasoline-powered machinery ONLY outdoors and away from windows. 

• Play it safe. Additional flooding or flash floods can occur. Listen for local warnings and information. If your car stalls in rapidly rising waters, get out immediately and climb to higher ground. 

• Return home only when authorities indicate it is safe to do so. 

• Roads may still be closed because they have been damaged or are covered by water. Barricades have been placed for your protection. If you come upon a barricade or flooded roadway, go another way. 

• Stay on firm ground. Moving water only six inches deep can sweep you off your feet. Standing water may be electrically charged from underground or downed power lines. 

• Flooding may have caused familiar places to change. Floodwaters often erode roads and walkways. Flood debris may hide animals and broken bottles, and it’s also slippery. Avoid walking or driving through it. 

• Be aware of where floodwaters have receded. Roads may have weakened and could collapse under the weight of a car. 

• Stay out of any building if it is surrounded by floodwaters. 

• Use extreme caution when entering buildings; there may be hidden damage, particularly in foundations. 

A flood can cause physical hazards and emotional stress. You need to look after yourself and your family as you focus on cleanup and repair. 

• Avoid floodwaters; water may be contaminated by oil, gasoline, or raw sewage. 

• Service damaged septic tanks, cesspools, pits and leaching systems as soon as possible. Damaged sewer systems are serious health hazards. 

• Listen for news reports to learn whether the community’s water supply is safe to drink. 

• Clean and disinfect everything that got wet. Mud left from floodwaters can contain sewage and chemicals. 

• Rest often and eat well. 

• Keep a manageable schedule. Make a list and do jobs one at a time. 

• Discuss your concerns with others and seek help. Contact the Red Cross for information on emotional support available in your area. 

• Turn off the electricity at the main breaker or fuse box, even if the power is off in your community. That way, you can decide when your home is dry enough to turn it back on. 

• Get a copy of the book, Repairing Your Flooded Home from the American Red Cross. 

• Contact your insurance agent to discuss claims. 

• Listen to your radio for information on assistance that may be provided by the state or federal government or other organizations. 

• If you hire cleanup or repair contractors, check references and be sure they are qualified to do the job. Be wary of people who drive through neighborhoods offering help in cleaning up or repairing your home.