A new study led by Abt Global and the National Center for Atmospheric Research in Boulder, Colorado projects increasing flood damages resulting from continued unmitigated greenhouse gas emissions.
 
The study, published in Natural Hazards and Earth System Sciences, assessed future inland flood risks and associated damages by first tabulating the value of assets within each of the mapped flood hazard zones throughout the U.S. The research team then used hydrologic projections based on climate models from two greenhouse gas (GHG) emissions pathways – an aggressive GHG mitigation scenario and a higher GHG scenario – to project changes in the frequency of future inland flooding events under each scenario.
 
In the GHG mitigation scenario, the average estimated cost of inland flood damages is projected to grow from approximately $3 billion annually to $4 billion annually by 2100. In the higher GHG scenario, inland flood damages are projected to increase to more than $7 billion annually by the end of the century.
 
Based on the study results, not all regions of the U.S. face the same projected changes in flood risk. For example, in the higher emissions scenario the upper Midwest and Great Plains saw smaller projected changes in inland flooding, while the largest changes were noted for the Southern Appalachians, the Ohio River valley, and much of the western United States. By the end of the 21st century, many of the rivers in those regions were projected to experience “100-year” floods up to five times as frequently in the higher emissions scenario. In other words, inland flood events that currently have a 1 percent chance of occurring each year in those regions could have more than a 5 percent chance of occurring each year under the higher emissions scenario.