Changing your home's details on Flood Factor

Learn what information you can provide to our Help Center that may affect your Flood Factor and help make our data more accurate 

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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 data. 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.

Data that will help improve the Flood Model

You know your property better than anyone! If you have information you think might be helpful to improve our Flood Model, please let us know by submitting a request through our contact forms. Please note that this information will not change your property's Flood Factor, but it can help improve the accuracy of the First Street Foundation Flood Model, and the information shown on Flood Factor. In order to improve our Flood Model, please reach out if you notice any of the following issues:

Incorrect FEMA Zone

If you believe Flood Factor has listed the incorrect FEMA flood zone for your property, please submit a Letter of Map Amendment (LOMA). The FEMA zone information listed on Flood Factor is provided by MassiveCert Inc and is currently an estimated zone. We recommend working directly with MassiveCert or another similar company to acquire the Flood DeterminationCertificate for a property or to get the determinations reversed. MassiveCert has services nationwide for a Letter of Map Amendment as well as an application process for providing elevation data for a property should FEMA’s elevation data be wrong.

Missing flood control features

Our team is continuing to conduct research on flood control projects around the country and will be continually updating the model based on new information. While our database contains 23,000 features today, we acknowledge there are more to include, and value your input!

If you have knowledge of specific completed projects, precise service area extents-of-flood adaptation infrastructure, or spatial data on flood adaptation infrastructure,  please help the team by providing any level of detail you can here. Certain information about flood control projects are particularly useful, such as: 

  • Name of the flood control project
  • Entity in charge of the project (local government, FEMA, USACE, etc.)
  • Address or specific location  
  • Images
  • Links to local, state, or federal documents outlining project details, including the flood event it protects for
  • A map showing the geographic area the project protects, including the physical location of the flood control project

New projects can be included for our next update to improve the model! If you would like to read about examples of flood control projects and how grey infrastructure works to alleviate flooding please review this article


Example of a levee; an embankment built to prevent the overflow of a river. Levees can also be built along low-lying coastal areas.

Missing historic flooding event

Flood Factor uses data from the First Street Foundation, which has modeled 55 major river and storm surge floods in the U.S. from  2001 on, and is continually adding more. Historic events in the First Street Foundation Flood Model are recreated using hydraulic models and public data sources. Historic river flooding events are recreated by analyzing historical USGS stream gauge readings during identified flood events and then compared to recorded high water marks and insurance claims of flooding made during that event. Coastal flooding events are recreated by analyzing storm surge, tides, coastal circulation, wind-generated waves, and geospatial analysis for specific storms, such as Hurricane Katrina. The recreation is then compared to recorded high water marks during the event. 


                                                                            Aftermath of Hurricane Gustav - August 2008

If you have knowledge of specific historic flooding, we'd love to hear from you. We will investigate historic flooding this area further and incorporate any new events determined into our future update. 

In order to include historic events in our Flood Model please reach out to us through our Help Center and provide:

  • Dates the event took place
  • Location of historic flooding
  • Any pictures that may show the depth and damage of the flood
  • News articles that describe the flooding your property experienced 

Naming Mismatch

We understand you may have questions regarding names of locations related to your property. The First Street Foundation Flood Model matches parcel data from official government sources to address data collected from commercial sources. Naming conventions attached to specific parcels and addresses may not exactly match, resulting in naming discrepancies. Here is a link to the methodology behind our research.

If you have knowledge of specific location names, we'd love to hear from you. Please submit a ticket through the Flood Factor Help Center that includes:

  • A corrected address that includes the house number, street address, zip code, city, and state
  • The incorrect address listed on 

We will review the issue further and be sure to update any issues found during a future update. Please take a look at how we update Flood Factor data.


Learn more

The data behind Flood Factor

The First Street Foundation Flood Model

Flood Factor improvements and updates




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