Understand how flood risk to residential properties affect an area’s risk.
Flood Factor scores within a community may vary dramatically depending on each property’s elevation or distance to water sources, such as lakes, rivers, or oceans. While one property may have minimal risk and likely be safe from flooding, other properties in the local community may be at risk. Even adjacent neighbors can have very different levels of flood risk. Flood damage to residential properties can impact day to day life within a community and may impact the overall economic well-being of an area.
How flood risk to residential properties are determined
To determine residential risk of flooding, the number of residential properties are calculated and compared to the total number of properties within that location to determine the area’s proportion of residential properties at risk. That location is then compared to similar geographies across the country and represented as Minimal, Minor, Moderate, Major, Severe or Extreme risk.
Residential risk is based on property Flood Factors. Flood Factors are not only a score ranging from 1-10 risk rating, it is a comprehensive risk assessment that includes a property's cumulative, probabilistic thirty-year risk of flooding from high intensity rainfall, overflowing rivers and streams, high tides, and storm surge. A property’s Flood Factor is determined by its likelihood of flooding and the potential depth of that flood. Flood Factor scores also take into account the risk-mitigating effects of levees, dams, open spaces, and other adaptation measures.
The First Street Foundation Flood Model includes publicly available and 3rd party data to identify property boundaries and building footprints. A property boundary is the outline of the individual lot of land, while building footprints refer to the outline(s) of building structures on a property. Along with elevation data, this information is used to determine the likelihood of water on the ground reaching the lowest point of a building’s footprint.
Flood Factor also takes into account how flood risks are likely to change over the next 30 years due to our changing environment. This means even a property that hasn’t flooded in the recent past may still face flood risk in the future.
Flood damage to residential properties can impact day to day life within a community and may impact the overall economic well-being of an area. Floods that impact infrastructure and businesses or block roads and will also impact the finances of homeowners.