A recent study has highlighted a surprising twist in flood management: building dams in coastal estuaries, rather than mitigating flood risks, might actually exacerbate them. Published in the Journal of Geophysical Research: Oceans, the research challenges the conventional wisdom about dams and their role in flood prevention.
The study, which focuses on Charleston Harbor in South Carolina, shows that coastal dams—often constructed to counteract the effects of severe storms, saltwater intrusion, and rising sea levels—can sometimes increase flood risks. By analyzing historical data and modern measurements, researchers found that the impact of these dams on flood severity varies depending on storm surge duration and water flow dynamics.
Lead author Steven Dykstra, an assistant professor at the University of Alaska Fairbanks College of Fisheries and Ocean Sciences, explained, “The typical assumption is that storm surges diminish as they move inland. However, the unique shape of estuaries can actually amplify the surge.”
Estuaries, which often funnel water as they extend inland, can experience heightened flood risks when a dam is introduced. This is due to the way dams alter the estuary’s shape, reflecting and amplifying storm surge waves similar to how water splashes in a bathtub.
Using Charleston Harbor as a primary case study, the researchers applied computer models to assess flood responses in 23 different estuaries, both with and without dams. The findings revealed that estuaries with dams often see increased wave heights and flood risks due to their altered shapes.
Interestingly, the study also found that regions far from coastal dams can still be affected by these structures. In Charleston, significant storm surges were recorded over 50 miles inland, indicating that coastal infrastructure impacts extend beyond their immediate vicinity.
Dykstra noted, “One alarming realisation is that people living far inland might not be aware of their vulnerability to coastal influences. As sea levels rise, these effects are becoming more pronounced, often resulting in severe flooding.”
The research, with contributions from Enrica Viparelli, Alexander Yankovsky, and Raymond Torres from the University of South Carolina, and Stefan Talke from California Polytechnic State University, underscores the need for re-evaluating how coastal infrastructure is designed and managed to better address flood risks.
