An FIU student has exposed a hidden driver of coastal flooding, and it could help improve warning systems for entire communities.
Earth and Environment Ph.D. student Dafrosa Kataraihya's latest research, published in Natural Hazards, shows that winds hundreds of miles away are a culprit of coastal flooding.
Kataraihya's research revealed a six- to 18-hour window of lag effect between the time wind patterns shift out at sea and when the water level rises at the shoreline. She used the National Oceanic and Atmospheric Administration (NOAA) and National Center for Atmospheric Research global models to analyze offshore winds and their correlation with sea levels over a 22-year period. She discovered that the local coastal wind people experience along the coastline has almost zero impact on whether sea levels rise or fall.
"That truly shocked us. We expected it to have some sort of an impact," she says. "When I go to the beach, I feel the wind — there's a land breeze, a sea breeze. That should have an impact."
Instead, the wind blowing further out at sea is the real culprit. These offshore winds accounted for 30 to 50 percent of the water level changes. The research also found a specific regional wind pattern that consistently showed up right before extreme high-water events, such as floods, or extreme low-water events across multiple states at once.
Another surprise finding in her research was that certain coastal stations near the Florida Current show no wind impact due to powerful ocean currents. In coastal flooding areas like Virginia Key and Key West, the Florida Current has a significant impact on sea level variability. In this area, wind showed to have no impact at all due to the powerful current coming from the Gulf of Mexico. Similar findings were found at Trident Pier near Port Canaveral, where strong currents, that eventually head toward Chesapeake Bay, override the wind's influence.
The researchers also looked at 12 specific angles relative to the coast and found that every city has a danger angle. If the danger angle is hit by wind out at sea, the risk of flood significantly increases.
This research is not only important for predicting possible floods but is also a vital tool for city planners. Kataraihya noted that current flood-warning systems, monitoring, and the drafting of future flood maps should all start paying more attention to offshore wind patterns rather than primarily focusing on local wind conditions.
Kataraihya is now developing forecasting models that use machine learning to predict sea level variability up to seven days in advance. She hopes to improve the model's accuracy and extend the prediction period, giving coastal communities critical information to stay safe.
How does the wind work?
Imagine a tray of water. If you blow at the edge of the tray, not much water moves. But if you blow steadily in the middle of the tray, you can push a large mound of water toward one side. Coastal flooding works much in the same way. Offshore winds can induce flooding, while local coastal winds have nominal impacts.
