66,441 residents·in Alameda County·568 flood claims county-wide
From the National Weather Service, checked 1 minute ago. Every active flood alert in the U.S. →
WHAT. Up to 1.6 ft of inundation above ground level is possible in low-lying areas near shorelines and tidal waterways.
WHERE. Bayshore locations along the San Francisco Bay and San Pablo Bay.
WHEN. Until 4 PM PST Friday November 13.
IMPACTS. High tides will result in flooding of low-lying infrastructure, isolated road closures, and coastal erosion. Rising tides will bring water and waves farther up the beach than normal, restricting escape from beaches and coastal areas.
ADDITIONAL DETAILS. At the San Francisco tide gauge, high tide is expected to be: 1.6 ft above normal (7.4 ft MLLW) at 10:06 AM Sunday 11/8, 1.6 ft above normal (7.4 ft MLLW) at 10:35 AM Monday 11/9, 1.5 ft above normal (7.3 ft MLLW) at 11:04 AM Tuesday 11/10, 1.4 ft above normal (7.2 ft MLLW) at 11:35 AM Wednesday 11/11, 1.4 ft above normal (7.2 ft MLLW) at 12:10 PM Thursday 11/12, 1.2 ft above normal (7.0 ft MLLW) at 12:49 PM Friday 11/13. These predictions include up to 1.5 ft of surge that will enhance the astronomical tide and flooding threat. High tide varies up to 90 minutes earlier or later along the Pacific Coast and through the San Francisco Bay, respectively.
What to do.
If travel is required, allow extra time as some roads may be closed. Do not drive around barricades or through water of unknown depth. Take the necessary actions to protect flood-prone property.
Is your address in the flood zone? Search it above for FEMA’s zone and base flood elevation. A new flood insurance policy usually takes 30 days to start (NFIP rule; exceptions include a policy bought when closing a mortgage), so one bought during a flood generally won’t cover it. Homeowners policies don’t cover flood.
Shaded areas are FEMA’s mapped flood hazard zones in and around Castro Valley CDP, California. Zoomed out they are simplified; at street level the map switches to FEMA’s exact layer. Tap anywhere to check that spot, or search an address above.
The map above shows FEMA’s flood zones in and around Castro Valley CDP; tap any spot, or search an address, for the exact zone. FEMA’s flood insurance records are kept by county, not by city, so the numbers below are for all of Alameda County, which includes Castro Valley CDP.
9% of Alameda County’s area is in FEMA’s high-risk flood zones, and another 3% in shaded X (mostly the 0.2% floodplain and areas behind levees).
45% of Alameda County’s flood insurance claims were on properties rated outside FEMA’s high-risk zones.
320 NFIP claims with a recorded rated flood zone, 1978 to date. The zone is the one FEMA used to rate that policy, which may not match today’s map. Source: OpenFEMA NFIP claims.
In Alameda County flood insurance claims that reported a flood depth, the average was 11 inches.
Drawn to scale against an 80-inch door. Even a few inches soaks flooring, the bottom of the drywall and anything plugged in near the floor.
Average of the depths reported on the county’s claims (zero and implausible values left out). Source: OpenFEMA NFIP claims.
The worst year was 1998, with 103 claims and $1.1M paid, the year of Severe Winter Storms and Flooding.
Bar height is scaled by square root so ordinary years stay visible next to the worst one. NFIP claims by year of loss. Source: OpenFEMA.
Full Alameda County flood history: disasters, storm reports and events →
If a building is in a high-risk zone (A or V) and its mortgage comes from a federally regulated or insured lender, or is federally backed, flood insurance is required.
The average NFIP premium across California was $1,033 a year on August 31, 2026 (premium plus the federal policy fee; the reserve fund assessment and HFIAA surcharge come on top). Risk Rating 2.0 prices each building on its own flood risk, so a quote can be far from the average.
Outside the high-risk zones it is optional, and often worth having: from 2014 to 2024 nearly one-third of NFIP claims came from outside the high-risk Special Flood Hazard Area. Quotes: FloodSmart.gov or a local agent.