A recent study conducted by scientists at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science found that over two million acres of floodplain have been developed over the past two decades in the United States. Approximately half of all new floodplain housing was built in Florida, which is especially prone to flooding. By combining geospatial land use, impervious surface, and housing data with digitized regulatory floodplain maps, researchers were able to measure new floodplain development across the country. The study, published in Earth’s Future, revealed that over 840,000 new residential properties were built in the floodplain, with 398,000 of those being in Florida.
Lead author Armen Agopian, a Ph.D. student at the Rosenstiel School, noted that the amount of new housing in floodplains was lower than expected given the size of the floodplains and overall housing growth. If new housing were distributed proportionally to the share of floodplain land in Florida, they would have expected to see 40% of new housing built in the floodplain. The study also found that 74% of communities in the U.S. have limited new development in floodplains, with coastal communities more likely to concentrate new development and housing in floodplains compared to inland communities. Additionally, communities participating in FEMA’s Community Rating System were found to have a higher likelihood of floodplain development.
The study highlighted the importance of improving floodplain management practices to limit floodplain development. Communities with a flood problem that enroll in FEMA’s Community Rating System need to not only participate but also improve their floodplain management practices to support safer development patterns. Development in flood-prone areas is a significant driver of increases in flood-related damage, which can increase the likelihood and severity of harm when floods occur. This study is the first comprehensive dataset measuring floodplain development outcomes community by community nationwide, focusing on areas that have avoided flood problems by taking smart actions early on.
Senior author of the study, Katharine Mach, emphasized the importance of learning from communities that have successfully avoided flood problems by avoiding development in floodplains from the beginning. Many communities across the nation have taken proactive measures to limit floodplain development, despite less attention being paid to their efforts compared to places that have experienced major flood events resulting in destruction and loss of life. The study was supported by National Science Foundation grants, the Leonard and Jayne Abess Center for Ecosystem Science and Policy, and the Rosenstiel School of Marine, Atmospheric, and Earth Science. This research provides valuable insights into floodplain development patterns in the U.S. and the need for improved floodplain management practices to mitigate flood-related damage.