One of the consequences of a changing climate is more extreme weather patterns, which can intensify precipitation and flooding events. Understanding where flooding is more or less likely to occur in the future can help identify vulnerable communities so that they may better prepare.
Flood risk scores are from the First Street Foundation Flood Model. First Street Foundation determines the flood risk score by combining hydraulic and hydrology models along with climate change projections. This creates a risk score range from 1 to 10. More information on their methodology is available in their flood model documentation.
Environmental risk data is provided by Risk Factor™ a product of First Street™. Risk Factor models are designed to approximate risk and not intended to include all possible scenarios.
Historical data is not available for this indicator.
Go to: Flood Risk Map | Flood Risk Now
Flood Risk Map
Projected likelihood of flooding in next 30 years, score out of 10
Source(s): First Street Foundation, Flood Model, 2022; U.S. Census Bureau, Geography Division 2020 TIGER/Line Shapefiles
Insights & Analysis
- The four census tracts with the highest average flood risk score are all adjacent to either the Puyallup or Green rivers.
- The census tracts with the highest flood risk score are along the Puyallup river in Puyallup, Pierce County (9.1); Kent just south of the Green River Natural Resources Area (NRA), King County (7.6); Kent including the Green River NRA, King County (7.5); again along the Puyallup River in Puyallup, Pierce County (7.1).
- Pierce County has the highest average flood risk score (1.9), followed by King (1.5), Kitsap (1.5), and Snohomish (1.5).
- Of the region’s population, 2% live in the top 20 census tracts with the highest flood risk scores (10 tracts are in King County and 10 are in Pierce County).
- Five rivers drain into the Puget Sound in the region - the Duwamish, Nisqually, Puyallup, Snohomish, and Stillaguamish rivers.
Source(s): First Street Foundation Flood Model, 2022; U.S. Census Bureau, 2017-2021 American Community Survey 5-Year Estimates, Tables B02001, C17002, B22010, B11005, B11007, C16002
Note 1: Horizontal axis (low, medium, high) denotes concentrations of each community. See, "How is equity measured?" for more information.
Note 2: For Households with Limited English Proficiency, the low and low medium categories have the same value in Kitsap County. There are more census tracts in those places estimated to have 0 households with limited English proficiency than the number of tracts in the low quintile category. The values for the low and low medium categories were averaged.
Insights & Analysis
- In the region, communities with high concentrations of people of color have an 11% lower average flood risk score than those with low concentrations.
- In King County, communities with high concentrations of people with disabilities have a flood risk score almost 40% higher than those with low concentrations.
- In Pierce County, communities with high concentrations of people with disabilities have a flood risk score almost 20% higher than those with low concentrations.
- In Snohomish County, communities with high concentrations of people of color have a flood risk score 40% lower than those with low concentrations.