Ready Your Home for Flooding

Winter storms, high tides and saturated ground can flood streets and homes across San Mateo County. Whether you rent or own, this page helps you protect your home and belongings and choose the right flood supplies.

For alerts, sandbag sites and what to do when a storm is coming, see Flood Preparedness.
Download the Household and Renter Flood Checklist (PDF) Look up your hazards

Start With Your Risk

Enter your address in MyHazards to see flood and sea level rise hazards near you.

Map of San Mateo County showing sea level rise and flood hazard areas. Opens the Cal OES MyHazards address lookup. Look up your address in MyHazards

MyHazards is a Cal OES tool and opens in a new tab.

Protect Your Home, Step by Step

Start at the top. Sandbags work best as a backup, not a plan.

  1. Lift what matters. Move documents, electronics and valuables off the floor or into waterproof bins.
  2. Steer water away. Clear gutters and the storm drain by your home, point downspouts away from your foundation, and report clogged drains.
  3. Keep water out. Seal gaps around doors, windows and pipes. If water backs up through drains, toilets or sinks, a backflow valve can stop it. See Ask Before You Install.
  4. Get water out fast. Keep a portable pump or wet/dry vacuum on hand, run your sump pump if your home has one, and place a flood sensor that alerts your phone.
  5. Last line: barriers and sandbags. Set up door dams or sandbags when a storm is forecast. They slow water but don't stop it. Find free sandbags on Flood Preparedness.

Get Your Home Ready

Actions to Take Today

  • Store belongings in waterproof bins on shelves, not on the floor.
  • Keep documents, medications and electronics where you can grab them quickly, and keep digital copies.
  • Photograph or video your home and belongings for insurance.
  • Get a removable door dam or water-absorbing barrier.
  • Place a plug-in flood sensor near water heaters, washers or low doors.
  • If your home has a sump pump, find it and learn how to turn it on.
  • Buy flood coverage for your belongings. Most home and renters policies don't cover flooding, but renters can buy contents-only flood insurance. Learn more at FloodSmart and United Policyholders.

Ask Before You Install

If you rent, or your HOA manages your building, your property owner or manager decides on permanent changes like installing backflow valves or sump pumps, or raising appliances.

  • Ask whether your home or street has flooded before and what the owner plans to do in a storm.
  • Learn how to report drainage or building problems, save that number in your phone, and report problems in writing.

If You Own Your Home

  • Hire a licensed plumber to install backflow valves, and a licensed electrician to raise outlets, switches or your electrical panel.
  • Check with your city or County building department before you start. Some projects need a permit.
  • Install a sump pump with battery backup so it keeps working if the power goes out, and test it and its battery before winter.
  • Raise water heaters, washers, dryers and outdoor AC units at least 1 foot above the level floodwater could reach.
  • Talk with your neighbors before you regrade your yard or extend downspouts toward a property line. Water you move can flood their property.
  • Ask the previous owner whether the home has flooded before.

Renters: Flood Information in Your Lease

California law requires residential leases signed on or after July 1, 2018 to include certain flood information. Look for it in your lease, and use MyHazards (above) to look up your address.

For more information:

Storm conditions and other details can change quickly. Always confirm with the responsible agency. This page shares general preparedness information and doesn't replace instructions from emergency officials.

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