Flood Model Methodology - Calculating property-level risk

Have more questions? Submit a request

First Street Foundation’s Flood Model uniquely considers the risk of flooding from rainfall and climate change; finding 6 million properties face substantial risk unaccounted for by FEMA.

First Street Foundation’s peer-reviewed model was created thanks to an unprecedented partnership of more than 80 world-renowned scientists, technologists and analysts. The Flood Model determines a property’s risk from all major types of flooding, including: high intensity rainfall, overflowing rivers and streams, high tides, and coastal storm surge. The model assigns each property a Flood Factor, ranging from 1 to 10, based on its cumulative risk of flooding over a thirty-year mortgage. Search your property on RiskFactor.com to learn if your home is at risk.

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. 

mceclip0.png

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.

mceclip1.png

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. 

mceclip2.png

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.

Want access to our data?

You can get access to the most comprehensive property-level flood risk data set in existence.

For commercial use or non-profits, academics, or public sector professionals needing data at a property-level, First Street Foundation provides access to property-level data for purchase. Learn more

For nonprofits, academics, and the public sector, aggregated flood risk summary statistics are now available for public, noncommercial use through the AWS Registry of Open Data and on ESRI’s Living Atlas and Maps for Public Policy sites. Learn more.

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.

 

Press Coverage

The New York Times - New Data Reveals Hidden Flood Risk Across America

The Washington Post - Millions of homeowners face flood risks without realizing it, and climate change is making it worse

 

Learn more

How is my Flood Factor calculated?

Data sources used to determine a property's Flood Factor

The Nation's first flood adaptation database

 

Articles in this section

Was this article helpful?
5 out of 8 found this helpful
Share