Integrating Climate Consequences from Flood Risk into Future Population Projections

Abstract Population exposure to flood risk has been linked to property value decreases, negative health/well-being consequences, and both short and long term population displacement resulting in shifts in population size and composition. To date, research in this area has examined this issue on a case-by-case basis, or at a level that generally hides the observed patterns associated with population shifts within housing markets. Using historic flood exposure and current flood risk data, we identify relationships between exposure to flood risk and population change. Using those observed relationships, in conjunction with future climate adjusted population projections, we forecast future population levels and changes to the underlying population in 2055. We find that declines in population size are associated with exposure to flood risk, particularly in areas with high climate vulnerability. Specifically, several high risk locations have already begun to see population responses to flood exposure and are forecast to have uneven growth directly related to future risk. These locations include some of the most populated areas in the US, including the states of Florida, Texas and California. We also find that population growth rates in communities that are exposed to high frequency flooding (5 and 20 year return period risk) are 2-7% lower than baseline. This finding is exacerbated in areas at disproportionate risk of the most frequent flooding where growth is expected to reverse and decline over the next 30 years.