Cost of Flooding was developed by the Federal Emergency Management Agency (FEMA) to assess a community’s risk from flooding on an annual basis. Data was downloaded at the county level and integrates a community’s population size, property values, and agricultural value (FEMA, 2023). This indicator is a useful economic measure of the likely annual costs of flooding.
How is it scored?
Scores at the county-level were calculated by comparing counties in southeast Michigan to percentiles (0, 25th, 50th, 75th, and 100th) of FEMA index scores for all of Michigan. We converted these FEMA index scores to a 0–100 scale using threshold-specific equations (Table 1).
Table 1. Equations used to convert FEMA Index scores to a 0–100 scale based on percentiles (0, 25th, 50th, 75th, and 100th) for all Michigan counties.
FEMA Index Threshold | Report Card Score | Equation |
< 2.68 | 100–75 | y = -9.3284x + 100 |
< 6.04 | 74–50 | y = -7.4405x + 94.94 |
< 7.91 | 49–25 | y = -13.369x + 130.75 |
< 43.85 | 24–0 | y = -0.6956x + 30.502 |
County-level scores were population weighted and summed to calculate the watershed score. Watershed scores were weighted by their population size to calculate an overall score for southeast Michigan.
Data source: https://hazards.fema.gov/nri/riverine-flooding