What is the First Street Foundation Flood Model and how is it used to calculate my home’s Flood Factor?

Learn about the First Street Foundation Flood Model and how it calculates your home’s Flood  Factor. 

The data behind Flood Factor

The First Street Foundation Flood Model is a peer-reviewed model used by Flood Factor was created thanks to an unprecedented partnership of more than 80 world-renowned scientists, technologists and analysts. 

The model allows Flood Factor to incorporate risk from all major types of flooding, including: high intensity rainfall, overflowing rivers and streams, high tides, and coastal storm surge. Because these different flood types are often interconnected, they are first analyzed independently, then “coupled” together where appropriate. 


Flood Factor scores within a neighborhood may vary depending on each property’s elevation or distance to water sources, such as lakes, rivers, or oceans. 

A property’s Flood Factor is determined by its likelihood of flooding and the potential depth of that flood. The First Street Foundation Flood Model uses elevation, climate, proximity to water, adaptation and flood history to calculate the likelihood of flooding for a specific geographic location. In terms of elevation, the Flood Model uses individual county Digital Elevation Models (DEM) and The National Elevation Dataset (NED) managed by the United States Geological Survey (USGS) to determine projected flood depth for properties.

Flood Factor simplifies this complex flood risk data into an easy to understand score that helps people protect themselves and their property. Put simply, a Flood Factor is a 1-10 scoring, from minimal to extreme, that tells you a property’s potential risk of flooding at least once over the life of a 30 year mortgage.


A property’s Flood Factor indicates their risk of experiencing flooding, at least once, over the course of a 30 year mortgage.

Flood Factor identifies risk over the length of a typical mortgage

Flood Factor aggregates how risks are accumulating and changing over time which means even very small chances of flooding today can add up to bigger chances over time. 

All properties have a Flood Factor of at least 1, and the higher the property’s Flood Factor, the larger the property’s likelihood or depth of flooding over the next 30 years. 


A Flood Factor indicates a home’s likelihood or depth of flooding. Put simply, a property with a Flood Factor of 9 is more likely to flood, or “land” on flood, than a property with a Flood Factor of 3.

The reality of a changing climate means every property has at least some risk of flooding over time, even if that risk is extremely low. For this reason, Flood Factors do not start at zero -- a Flood Factor of 1 captures even extremely minimal risk over time.

Continuously improving over time 

The projections shown on Flood Factor come from the First Street Foundation Flood Model. First Street Foundation has made its flood model’s full technical methodology available to the public because it supports scientific collaboration and data transparency. Like all flood models, its projections are intended to help provide a fuller understanding of flood risks, and we encourage you to supplement this information with additional research. We are committed to the accuracy of our data and will continue to grow, adapt, and incorporate feedback and expand its model over time, including an annual data update.


Learn more

How is my Flood Factor calculated?

Where does the information on Flood Factor come from?

Adaptation measures and how they are included in flood projections


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