Is My Property At Risk in Flood Zone AO? Risks and Costs Explained

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Flood zone AO is an area near a river or stream with a high potential for flooding due to shallow sheet flow. Floods typically occur in areas with sloping land with average depths of one to three feet. Homeowners living in AO zones are required to purchase flood insurance if they have a mortgage through a federally regulated or insured lender. 

Key Takeaways

  • On a flood map, flood zone AO signals an area with a 1% chance of experiencing a flood in a given year.
  • Homes in zone AO are particularly vulnerable to flooding caused by sheet flow with average flood depths up to three feet.
  • Homeowners with a government-backed mortgage in flood zone AO are required to buy flood insurance, although private carriers may also enforce this requirement.
  • The average cost of NFIP flood insurance in Zone AO is $1,706.45 per year.

What Is Flood Zone AO?

The Federal Emergency Management Agency (FEMA) has designated flood zone AO as an area with a 1% annual chance of flooding or a 26% chance over a 30-year mortgage. Flood depths typically range from one to three feet and are typically caused by sheet flow on sloping terrain.[1] Sheet flow occurs when water falls in a thin layer over ground with a gentle slant and then pools if the area does not have defined drainage systems.

Homeowners in Zone AO are required to buy flood insurance if they have a government-backed mortgage but private mortgage lenders may enforce this requirement, as well.

Is Flood Insurance Required in Flood Zone AO?

Since FEMA has designated flood zone AO as a Special Flood Hazard Area (SFHA), homeowners in this area must buy flood insurance if they have a government-backed mortgage.[2] However, private mortgage lenders may also enforce this requirement due to the high risk of flood hazards.

Even if you live outside an SFHA, you may still want to consider buying flood insurance. 

Low-risk flood zones have reduced flood risks but the possibility is not entirely eliminated. Just one inch of floodwater can cause up to $25,000 in damages according to FEMA.[3] These damages will not be covered under standard homeowners insurance.

Where Can I Get Insurance for Flood Zone AO?

Standard homeowners insurance does not cover flood damage so you will need to buy flood insurance if you live in flood zone AO. Even if if you have a mortgage does not require it, it is always beneficial to have coverage for flood-related losses. Standalone policies are available from either the National Flood Insurance Program (NFIP) or a private insurance company. 

NFIP Flood Insurance

NFIP policies are commonly purchased because they are widely available, purchasable in 23,000 communities nationwide.[3] If you want higher coverage limits, then an NFIP policy may be a good option, offering up to $250,000 of building coverage and $100,000 of personal contents coverage for a single-family dwelling.[4] 

Private Flood Insurance 

One advantage of private flood insurance is that you can pay extra for replacement cost coverage for your personal property, which reimburses lost items at the price to buy it off the shelf today.[5] Meanwhile, NFIP policies only cover the item’s actual cash value, which deducts for depreciation factors like age and wear and tear.[6] Also, private insurers may sell policies with coverage limits higher than what the NFIP offers.

How Do I Know if My Home Is in Flood Zone AO?

Generally, zones AO are located near bodies of water like a river or stream but it can be any area vulnerable to sheet flow — again, thin sheets of water flowing over sloping terrain.[1] The FEMA website has online flood insurance rate maps that allow you to enter your zip code and see flood zone designations in your area. 

Zone AO

Source: New Hampshire Dept. of Business and Economic Affairs

How Much Is Flood Insurance in Flood Zone AO?

The average cost of NFIP flood insurance in Zone AO is $1,706.45 per year according to February 2022 data by FEMA.[7] Zone AO flood insurance rates are quite high due to the increased risk of flooding with average depths of one to three feet.[1] However, the actual cost can vary significantly based on your level of coverage, your property's replacement cost value and its location.

The average cost of NFIP flood insurance in Zone AO is $1,706.45 per year.

Cheaper flood insurance premiums may be available from private flood insurance providers. Below are sample rates in Florida provided by The Flood Insurance Agency:

Flood Zone

Annual Premium Quote

B, C, X zones


All A zones


All V zones


Source: The Flood Insurance Agency (TFIA)
*For $250,000 building coverage and $100,000 personal contents coverage

How Do Flood Zones Affect Home Insurance Costs?

After the implementation of Risk Rating 2.0 in 2021, FEMA uses flood zones primarily for designating SFHAs, which would indicate which homes require flood insurance. They are no longer used in calculating NFIP policy premiums.[8] Instead, premiums are determined by the property's specific features, such as:

  • Foundation type
  • Height of lowest floor relative to base flood elevation
  • Replacement cost value of the home's structure
  • Historical losses

Find Affordable Homeowners Insurance Rates

What Does a Flood Zone Mean in Relation to Risk?

The letters preceding a flood zone signal whether your home is located in a low- or high-risk zone:[9]

  • Zones preceded by letters B, C and X: Moderate- to low-risk flood zones with no flood insurance requirement for homes with government-backed mortgages.
  • Zones preceded by letters A or V: Special Flood Hazard Areas with a high risk of experiencing a flood in a given year. Flood insurance requirements apply for homes with government-backed mortgages.

Tips for Homeowners in Flood Zone AO

The following tips can help you protect your home and personal belongings, especially in a high-risk flood zone, like Zone AO:

  • Document all of your personal belongings and their value.
  • Store valuables and critical documents in waterproof containers above the base flood elevation.
  • If possible, elevate utility systems (e.g., furnaces, water heaters) at least 12 inches above the base flood elevation.[10]
  • Consider replacing carpeting with water-resistant tiles.
  • Seal basement walls with waterproofing compounds.
  • Prevent pooling water by installing flood vents in enclosed areas (e.g., foundation walls, garages).
  • Consult with a plumber to clear pipes of any backed-up sewage.
  • Secure outdoor furniture to prevent them from being swept away during a flood.
  • Seal cracks and gaps in windows, doors and gaps around pipes.
  • Elevate your home with stilts or piers.
  • Build new homes away from water sources, like rivers and shorelines.
  • Landscape your yard so it slopes away from your home and detached structures.
  • Coat your walls in water-resistant sheathing.


What is AO flood zone meaning?

Zone AO is a flood zone designation with a 1% annual chance of experiencing a flood, usually caused by thin sheets of water cascading over sloping terrain. As a Special Flood Hazard Area, residential property owners in this high-risk flood zone are required to buy flood insurance if they have a government-backed mortgage.[2]

What is the best flood zone designation?

Zone X is generally considered a low- or moderate-risk zone with a 0.2% chance of flooding in a given year. Flood insurance requirements will not be enforced on residential properties in this zone.

What is the highest flood zone?

Zones preceded by the letters A or V are considered zones with a high risk of flooding — usually 1% or greater.

What does BFE stand for in flood zones?

Base flood elevations (BFE) on flood maps represent how high water is expected to rise during a flood. The base flood elevation for Zone AO, for example, ranges between one and three feet.[1]


  1. Federal Emergency Management Agency. “Zone AO.” Accessed May 1, 2023.
  2. Federal Emergency Management Agency. “Understanding Flood Risk: Real Estate, Lending or Insurance Professionals.”
  3. Federal Emergency Management Agency. “Flood Insurance.” Accessed May 1, 2023.
  4. Congressional Research Service. “National Flood Insurance Program: The Current Rating Structure and Risk Rating 2.0,” Page 9.” Accessed May 1, 2023.
  5. The Flood Insurance Agency. “Private Market Flood Policy,” Page 23. Accessed May 2, 2023.
  6. Federal Emergency Management Agency. “Fact Sheet: Understand What Your Flood Insurance Policy Covers Before Hurricane Season.” Accessed May 1, 2023.
  7. Federal Emergency Management Agency. “Flood Insurance Data and Analytics.” Accessed May 1, 2023.
  8. Congressional Research Service. “National Flood Insurance Program: The Current Rating Structure and Risk Rating 2.0,” Page 2, 16. Accessed May 2, 2023.
  9. Federal Emergency Management Agency. “Flood Zones.” Accessed May 2, 2023.
  10. Federal Emergency Management Agency. “Protect Your Property From Flooding,” Page 5. Accessed May 2, 2023.

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