Understand the broader impact flood risk has on your social well being.
The risk of flooding impacts more than an individual property. Flooding can impact the broader social and community buildings surrounding your home. Social risk assesses the effect of flood risk on social and cultural services.
How are operational thresholds used to determine social risk of flooding?
The First Street Foundation Flood Model is used to determine the risk of flooding from rain, rivers, tides, and storm surge to infrastructure. Flood risks are based on the likelihood of flooding, and the annualized expectation of flooding that reaches the building footprint or parcel centroid of each school, historical building, place of worship, government building and museum.The model then uses the average annual expected depth to each facility and checks if that depth is higher than the operational risk threshold. When a facility is flooded to the point where it can no longer function as intended, it is considered to have operational risk.
These thresholds vary depending on infrastructure type, as different types of infrastructure can withstand different depths of flooding while still maintaining some level of functionality. The operational threshold for historical buildings, places of worship, government buildings and museums is 0 inches, as these buildings are not typically designed to withstand flooding. However, the operational threshold of schools is 12 inches of flooding because schools are often designed to withstand some risk and function as shelters or a base of operations in case of emergency. Operational thresholds used are as defined in the FEMA’s HAZUS methodology.
For example, schools have an operational threshold of 12 inches while museums have a functional threshold of 0 inches. If both infrastructures are expected to flood 3.6 inches in the event of a 100-year flood, this depth of flooding would not exceed a school’s operational threshold of 12 inches, but would exceed the 0 inch operational threshold of a museum. This depth of flood could result in serious damage to a museum, causing it to no longer function as intended and likely close operation for a period of time. This is not to say a school would be undamaged, it may still suffer damage to its structure but 3.6 inches of flooding would not cause a school to be disabled or seriously damaged, and operations could continue.
Social risk in a geographic area is determined based on the percent of structures and the depth of flooding that causes a facility to be flooded at a depth that exceeds the functionality threshold, causing operational risk. The depth at which a certain percent of social infrastructures have operational risk is used to rank the level of risk resulting in a single social risk ranking for a community.
Social Risk rankings represent risk as Minimal, Minor, Moderate, Major, Severe and Extreme. Minimal risk is a case where no social infrastructures have flood risk. The depth of flooding which causes operational risk for each community level, neighborhood, zip code, city, and county; is then compared to the depth that causes operational risk for similar community levels within a state or across the country. County level social risk is ranked based on how their operational risk depth compares to counties across the county. While, neighborhood, zip code, city level social risks are ranked based on how their operational risk depth compares to communities within respective states.
What social infrastructure is considered in Community Risk?
Community Risk to social infrastructure includes schools, historical buildings, government buildings, places of worship, and museums. Each social risk infrastructure type is defined below.
- Schools - Flood risk to all Public elementary and secondary education facilities in the United States as defined by the Common Core of Data (CCD), National Center for Education Statistics (NCES ), US Department of Education for the 2017-2018 school year.
- Historical buildings - National historic places worthy of preservation. The National Register of Historic Places is the official list of America's historic and archeological resources.
- Government Buildings - All buildings or properties that are owned or leased by state level governments. It includes buildings occupied by the headquarters of cabinet level state government executive departments, legislative office buildings outside of the capitol building, offices and court rooms associated with the highest level of the judicial branch of the state government, and large multi-agency state office buildings.
- Places of worship - Places of worship are 501(c)(3) non-profit organizations that are included in the IRS master files of public national records.
- Museums - Includes 278 university and general higher education museums, collections and cultural heritage sites of scientific, artistic and historic significance