Flood Factor FAQ

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Answers to frequently asked questions regarding Flood Factor scores, accuracy, probabilities, and understanding of our risk assessments.

Risk Factor is a free online tool created by the nonprofit First Street Foundation® that makes it easy for Americans to find their property’s risk of flooding and understand how flood risks are changing because of a changing environment. Use Risk Factor to learn the annual and cumulative likelihood of water reaching your home so you can prepare for and mitigate risks before they become a reality.


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What is Flood Factor?

Flood Factor® is a free, easy-to-use online tool that makes it easy to learn about a property’s current and future risk of flooding, discover its flood history, and understand how its flood risk is changing over time because of a changing environment. A property's Flood Factor is not only a score ranging from 1-10, it is a comprehensive risk assessment including a property's thirty-year risk of flooding from high-intensity rainfall, overflowing rivers and streams, high tides, and storm surges. Properties with higher Flood Factors are either more likely to flood, more likely to experience high floods, or both. 

How accurate is Flood Factor?

Data on Flood Factor comes from the First Street Foundation Flood Model and was built upon decades of peer-reviewed research and developed in partnership with more than 80 world-renowned experts.  Like all flood models, it's intended to help identify potential flood risks, and Flood Factor users are encouraged to follow up with qualified professionals and supplement this information with additional research and documentation they might have.

The comprehensive model integrates all major flood types, from tides, coastal surges, rains, and rivers, and uses historical flooding events to validate risk. The model also considers future environmental changes, which FEMA itself has acknowledged the need to be integrated into its flood maps. 

How can I remove a property from Flood Factor?

Flood Factor is a product of the First Street Foundation, a non-profit committed to making flood risk information free and accessible to all. Properties cannot be removed directly through Flood Factor; however, we encourage you to share information that could impact your property's Flood Factor. This includes community flood risk reduction projects such as levees, seawalls, and pump stations. If something looks like it is missing or incorrect, please let the Flood Factor know by using the Help Center contact forms.

How often is Risk Factor updated?

The Risk Factor team is continuously working to refine its flood methodology and incorporate new information into Risk Factor. While the Risk Factor experience is updated regularly, a full Flood Model refresh occurs annually. Please note, as Risk Factor is updated, a property's Flood Factor, such as a score, may change. Learn more.

Why is my Flood Factor different from my neighbor’s?

Because Flood Factors are determined based on potential flood depths and 30-year flood likelihoods at the property parcel level, they often vary across and within neighborhoods. Even next-door neighbors can have significant differences in flood risks, largely due to differences in elevation, proximity to water or wetlands, and proximity to flood risk reduction projects.

One way to understand differences in risks is to switch to the map view on the flood risk explorer. By zooming in close enough, users can see both buildings' outlines as well as different flood scenarios. Properties with minimal Flood Factors shouldn’t show any flood water reaching the building outline in any flood scenario. Buildings in contact with deeper floods, or those with higher probabilities of flooding, will have higher Flood Factors. Learn more.

Are personal flood risk reduction measures like raising my home considered?

At this time, a property’s Flood Factor is based on the likelihood of water reaching a building, and as such, personal adaptation features such as raised homes are not included in the calculation.

If a home already has flood reduction measures in place, it may reduce the risk to its structure. We encourage users to work with local floodplain managers or engineers to best understand what level of risk personal flood reduction measures are built to withstand. Learn more.

Why do FEMA and Flood Factor have different flood risk assessments for my property?

Your FEMA zone and Flood Factor are two independent risk assessments. FEMA flood maps are used to determine insurance and building code requirements, whereas the Flood Factor is used to determine flood risk to the specific home today and into the future. 

While the findings of these models do not diverge starkly across the US, in some areas Flood Factor may show more or less flood risk than FEMA, simply because of differences in the methodologies employed. Flood Factor calculates flood probabilities on the property level and accounts for changing climate conditions. A core component of the model is its ability to include rainfall events as probabilistic flood risks. 

As a result, Flood Factor shows a more nuanced, property-specific flood risk, as opposed to a binary in-or-out of floodplain analysis from FEMA maps. Flood Factor uses publicly available flood risk information that shows how risk will accumulate and change over time. It is most powerful when used in conjunction with FEMA flood maps and other available state and local flood risk resources, and should be viewed as complementary to FEMA flood maps, which need to be used for building and permitting purposes. Learn more.

How similar or dissimilar are FEMA and Flood Factor across the country?

FEMA flood maps identify over 1.1 million miles of flood hazard areas, and while the maps can provide detailed information for homeowners on their flood risks, they are not available everywhere. Flood Factor’s national flood model shows that flood risk is more widespread in the United States, with over 24 million properties at risk over the next 30 years. Flood Factor also includes flood risk from extended periods of high-intensity rainfall, leading to urban stormwater flooding and storm surge. Additionally, future conditions are considered, such as sea level rise. Learn more.

Why is flood insurance recommended for my property?

While only FEMA maps can be used to determine flood insurance and building code requirements, both FEMA and Flood Factor recommend insurance regardless of the severity of risk because flood insurance is one of the best ways to protect against financial losses caused by flood events. It is also important to note that flooding is not included in standard homeowners insurance. Learn more.

Flood insurance is available to homeowners, business owners, and renters throughout the nation. Although flood insurance is only required for properties in high-risk FEMA flood zones, about 20% of all flood insurance claims come from properties outside these zones.

Will Flood Factor impact my property value?

A home is often your largest financial asset. This is why Flood Factor is dedicated to defining and communicating the flood risk facing every home in America. Flood Factor can help you, other individuals, and communities prepare for and mitigate flood risks before they become a reality.

What if my home has never flooded?

While a history of flooding in the past can be a great indication that it is likely to flood again in the future, many homes with high flood risks have never flooded before. One reason for this is that changes in the environment are increasing flood risks across the country.

Sell a home with flood risk

Before selling your home, you may be required to disclose the known hazards associated with the property. Among other hazards, this may include current and historic flood risk, location within a designated FEMA flood zone, and current flood insurance coverage. The specific requirements for disclosures change state by state, so it is best to check with your local authorities for the specific regulation.  

An important factor in selling a home with flood risk is understanding the costs to potential buyers. If the property is in a high-risk flood zone as designated by FEMA and purchased with a federally-backed mortgage, the property owners would be required to purchase a flood insurance policy as well. Generally, these flood insurance policies are provided through the National Flood Insurance Program (NFIP). These premiums may be lowered through investments in the home, such as elevating utilities or the home structure itself. If the property has been affected by a federally-declared disaster, it may be eligible to be purchased by local government programs. 

The impact of flooding on renters

Major flood events can pose a serious safety threat to all members of a community, requiring evacuations and causing damage to its homes, businesses, schools, and infrastructure, like roads, electrical grids, and sewage systems. Although renters may not have to worry about damage to their buildings, major floods can still ruin their belongings and create mold and other health hazards. Renters may also be impacted by nuisance flooding that occurs frequently but isn’t associated with a major flood event like the king tides experienced in many coastal communities. Nuisance floods often disrupt day-to-day life by limiting sidewalk access or closing roads, parking lots, and parks.

Most renters' insurance policies do not cover flood damage, so renters may want to purchase flood insurance policies to help fiscally protect themselves in the event of a flood caused by storm surges, heavy rains, overflowing rivers, or broken levees or dams. Some fiscal risk may exist, however, as neither renters insurance nor flood insurance covers living expenses incurred if a flood necessitates vacating their home. It's important to understand available flood solutions before a flood ever occurs.

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