What data sources are used to determine community risk of flooding?

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Community flood risk relies heavily on data from the United States government and the First Street Foundation Flood Model.

Community Risk measures the threat flooding poses to communities relative to other communities throughout the U.S. Even if your home is not at risk, flooding can still impact the broader social, commercial, and community infrastructure, and roads surrounding your home. Risk Factor™ allows individuals to understand the impact flooding has on your community. Because risks can vary for different levels of geographies, Risk Factor allows you to compare risks between these levels. 

The depth of flood water likely to reach each facility in a community is compared to the structure's operational threshold. If the depth of flooding expected to reach a facility is greater than its operation threshold it is flooded to the point where it can no longer function as intended and is considered to have operational risk. 

Data sources used to determine community risk 

Property and land use data are supplied through a partnership with Lightbox. Road centerline data are sourced from the US Census Bureau’s TIGER data. Infrastructure facility data are from a variety of sources including the US Environmental Protection Agency.

Flood risk

The First Street Foundation Flood Model is used to determine the likelihood of flooding from rain, rivers, tides, and storm surge to facilities, roads, and infrastructure based on a location’s history and geographic information, such as elevation, climate, changes in the environment, and adaptation measures.

Public infrastructure

  • Power station: Homeland Infrastructure Foundation-Level Data (HIFLD)
  • Wastewater treatment: The Agency for Toxic Substances and Disease Registry (ATSDR)
  • Superfund Site: Environmental Protection Agency (EPA) 
  • Water outfall: The EPA's National Pollutant Discharge Elimination System (NPDES)
  • Fire stations: The Homeland Infrastructure Foundation-Level Data Working Group (HIFLD)
  • Police station: The Homeland Infrastructure Foundation-Level Data Working Group (HIFLD)
  • Hospitals: The Homeland Infrastructure Foundation-Level Data Working Group (HIFLD)
  • Port: The Homeland Infrastructure Foundation-Level Data Working Group (HIFLD)
  • Airport: Federal Aviation Administration (FAA)

Social infrastructure

  • Schools: Common Core of Data (CCD), National Center for Education Statistics (NCES ), United States Department of Education (ED) 
  • Historical buildings: The National Park Service’s National Register of Historic Places (NIRS) 
  • Government Buildings: The Homeland Infrastructure Foundation-Level Data Working Group (HIFLD)
  • Places of worship: The Homeland Infrastructure Foundation-Level Data Working Group (HIFLD)
  • Museums: Worldwide Database of University Museums and Collections (UMAC) compiled by the ICOM committee 

Roads

  • TIGER, United States Census Bureau (USCB)

Residential and commercial properties

  • Property parcels and land use type: Lightbox, sourced from county assessors and recorders
  • Building footprints: Mapbox, sourced from Microsoft Bing and OpenStreetMaps

Operational Thresholds 

Many emergency services and critical infrastructure facilities are designed to maintain operations during minor flooding. To properly estimate the likelihood of interruption of operations, First Street has applied operational thresholds as specified in FEMA’s Hazus Program managed by FEMA’s Natural Hazards Risk Assessment Program (NHRAP) per facility type. This applies to utilities, emergency services, transportation facilities, and social infrastructure facilities. 

Infrastructure Type

Operational Threshold (inches)

Category

Residential parcels

  0 in 

  residential

Road centerlines

  6 in 

  road

Commercial parcels

  0 in

  commercial

Airport

  12 in

  infrastructure

Fire station

  24 in

  infrastructure

Hospital

  42 in

  infrastructure

Police station

  12 in

  infrastructure

Port

  12 in

  infrastructure

Power station

  24 in

  infrastructure

Superfund/hazardous waste site

  12 in

  infrastructure

Water outfalls

  0 in 

  infrastructure

Wastewater treatment

  0 in

  infrastructure

Government building

  0 in

  social

Historic building

  0 in

  social

House of worship

  0 in

  social

Museum

  0 in

  social

School

  12 in

  social

Levels available

  • Neighborhoods: Encompasses macro neighborhoods, neighborhoods, sub-neighborhoods, and residential districts (e.g. subdivisions and apartment complexes). Data is provided by a third-party data provider. 
  • Zipcodes: are zip code tabulation groupings of local areas as provided by U.S Census Bureau. 
  • Cities: Place (County Subdivision in New England) as provided by the US Census Bureau. Refer to a village, town, or city typically governed by a mayor and council.
  • Counties: County or county-equivalents as provided by the US Census Bureau.

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