A study led by the University of Miami unveils extensive floodplain development across the United Sates in the last two decades, emphasizing the need for improved floodplain management practices to mitigate potential risks.
A new study led by the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science has revealed that over 2 million acres of floodplain were developed across the United States in the past 20 years. Significantly, nearly half of this development occurred in Florida, where about 398,000 new residential properties were built on floodplains.
The research, published in the journal Earth’s Future, combines geospatial land use data with records from regulatory floodplain maps to chart new developments across the nation. Lead author Armen Agopian, a doctoral student in the Abess graduate program at the Rosenstiel School, and his team found that floodplain land accounted for 21% of all new housing built in Florida during this period, the highest total of any state in the United States.
“Given the size of floodplains and amount of new overall housing growth, those figures are actually much less than we would expect,” Agopian said in a news release.
If floodplain developments were proportionate to the actual share of floodplain lands in Florida, the state would have seen 40% of its new housing in these risk zones.
A considerable number of communities — 74% — have managed to limit fresh developments in floodplains, and 87% have restricted housing through local regulations. Notably, the study finds that coastal communities are more likely to concentrate new development in floodplains compared to inland areas.
One surprising insight from the study is regarding the Federal Emergency Management Agency’s (FEMA) Community Rating System (CRS). While the CRS incentivizes communities to adopt practices that can curb floodplain development in exchange for discounted flood insurance rates, participation alone was not found to ensure safer development patterns.
“Communities with a flood problem enroll in the program, but participating alone isn’t enough to support safer development patterns,” Agopian added. “Instead, communities need both to participate and to improve their floodplain management practices — those are the ones that start to limit floodplain development.”
The research underscores that development in flood-prone areas significantly increases the risk and severity of flood-related damage, affecting both residents and infrastructure.
This groundbreaking study is the first to provide such detailed, nationwide data on floodplain development, examining outcomes community by community. Historically, most flood research has concentrated on regions that have already experienced significant flood damage.
“What we find is that many communities around the nation have taken smart action early on, avoiding development in their floodplains from the start. There’s a lot we can learn from these communities that are often with little fanfare avoiding flood problems from the start,” senior author Katharine Mach, a professor and chair of the Department of Environmental Science and Policy at the Rosenstiel School, said in the news release.