The common practice of constructing dams to stop flooding can actually contribute to more intense coastal flood events, based on a brand new study.
The study, published within the Journal of Geophysical Research: Oceans, studied the consequences of dams inbuilt coastal estuaries, where rivers and ocean tides interact. Those massive infrastructure projects are surging in popularity globally, partly to assist offset intensifying storms, salt intrusion and sea-level rise fueled by climate change.
By analyzing data and measurements from Charleston Harbor, South Carolina, dating back greater than a century, researchers determined that coastal dams don’t necessarily mitigate flooding. Dams can either increase or decrease flood risks, depending on the duration of a surge event and friction from the flow of water.
“We often take into consideration storm surges becoming smaller as you go inland, however the shape of the basin can actually cause it to develop into larger,” said lead writer Steven Dykstra, an assistant professor on the University of Alaska Fairbanks College of Fisheries and Ocean Sciences.
Estuaries are typically shaped like a funnel, narrowing as they go inland. Introducing a dam shortens the estuary with a man-made wall that reflects storm surge waves moving inland. The narrowing channel shape also makes small reflections that change with the surge duration. Dykstra compared those storm-fueled waves to splashes in a tub, with certain wave frequencies causing water to slosh over the edges.
After using Charleston Harbor as a case study, researchers used computer modeling to gauge the flood response at 23 other estuaries in diverse geographic areas. Those encompassed each dammed and naturally occurring estuary systems, including Cook Inlet in Alaska.
The models confirmed that the basin shape and alterations that shorten it with a dam are the important thing component in determining how storm surges and tides move inland. At the correct amplitude and duration, waves in dammed environments grow as an alternative of diminishing.
The study also determined that areas removed from coastal dams could still be directly influenced by human-created infrastructure. Within the Charleston area, the best storm surges routinely occurred greater than 50 miles inland.
“Considered one of the scary things with that is that sometimes people do not understand they’re in a coastal-influenced zone,” Dykstra said. “Sea-level rise is making people far inland aware that they don’t seem to be free from coastal effects — and it often happens with a large flood.”
Other contributors to the study included Enrica Viparelli, Alexander Yankovsky and Raymond Torres from the University of South Carolina, and Stefan Talke from California Polytechnic State University, San Luis Obispo.
