Communities at Risk of Flooding

Flooding is expected to increase in the future as the effects of climate change increase. In this report, the Congressional Budget Office examines how projected flood risk varies across communities with different economic and demographic characteristics in two multiyear projection periods, one centered on 2020 and the other centered on 2050.

In the 2020 projection period (generally capturing current conditions), the prevalence of flood risk is 9 percent—that is, 9 percent of properties face at least a 1 percent annual probability of experiencing a flood of a depth of roughly 1 foot or more, CBO estimates. A 1 percent annual probability is equivalent to having about a one-in-four chance of experiencing at least one such flood over a period of 30 years. In the 2050 projection period, 10 percent of properties face that risk. Projections of flood risk are uncertain, and CBO aims to provide projections that are in the middle of a range of possible outcomes.

By CBO’s estimates, flood risk varies with communities’ characteristics in the following ways:

• Median household income. In general, projected flood risk is more prevalent in communities in which median household income is lower. Communities in which the majority of householders are Hispanic or Latino are an exception: In such communities, flood risk tends to be less prevalent where median household income is lower. (A householder is a person in whose name a housing unit is owned or rented.)
• Race. Risk is more prevalent in communities with a greater share of White householders, but communities in which most householders are Black (except for those in which the median household income is high) face the largest increases in flood risk from 2020 to 2050.
• Ethnicity. The percentage of properties exposed to flood risk is generally smaller in communities with a greater share of householders who are Hispanic or Latino.
• Type of residence. Flood risk is much more prevalent in communities in which the majority of the dwellings are secondary residences than it is in communities in which most dwellings are primary residences. The difference is larger in coastal areas than in inland areas. In communities with a greater share of renters, projected flood risk is less prevalent.
• Composition of household. In communities in which a greater share of households include someone age 65 or older, projected flood risk is more prevalent. Projected risk is less prevalent in communities with a greater share of households with children.
• Geographic location. The percentage of properties exposed to flood risk in coastal communities is more than twice that in inland communities, and coastal communities are projected to have greater increases in risk from 2020 to 2050. Of all the communities CBO analyzed, coastal communities in which the majority of dwellings are secondary residences have the highest percentage of properties exposed to flood risk.

Because of the nature of the available data, this report cannot identify causes of those variations across communities’ characteristics. Those causes may be complex and multifaceted because they involve questions of where people settle and why, and where governments invest in adaptive infrastructure and why.