Coastal flooding can seem unpredictable, but UCF Coastal researcher Ivan Haigh has found that recurrent coastal floods often occur at highly predictable times. Haigh, a professor in the Department of Civil, Environmental and Construction Engineering within UCF’s College of Engineering and Computer Science, recently led an international study examining how tides influence the daily impact of coastal floods.
In a recent study published in Nature Communications, Haigh and an international team of researchers found that coastal flooding tends to occur at certain times of day, reflecting the timing of the tides. While previous research has largely focused on the seasonal timing of river and coastal flooding, this is the first study to show that impact-causing floods have predictable daily timing across regions.
“Floods have traditionally been viewed as primarily weather-driven and therefore relatively unpredictable in their exact timing,” Haigh says. “But surprisingly little attention has been paid to what hour of the day flooding occurs. Another reason is the way we measure flooding. We commonly talk about the number of ‘flood days’ per year. Once an event is reduced to a flood day, the information about whether the flooding happened at 3 a.m., 8 a.m. or 3 p.m. disappears.”
Tides Create Predictable Patterns
Using tide gauge data and flood event records from the U.S. and the U.K., the researchers found clear patterns in when floods occur.
In Boston, for example, floods occur predominantly around noon and midnight, while in Southern California they are more common in the morning. In Florida, timing varies along the coastline because tides differ by location. Along the Atlantic Coast and toward the Florida Keys, coastal flooding is moderately predictable, while flooding along the Gulf Coast is less predictable.
Haigh says tides largely drive that predictability.
“In many locations, tides determine whether storm surge is sufficient to push water levels above flood thresholds,” Haigh says. “As a result, even storm-driven flooding often inherits the timing of the tides.”
The researchers found that the phenomenon isn’t limited to locations that experience semidiurnal tides, which consist of two high tides and two low tides each day. It also occurs in places with diurnal tidal systems — with one high tide and one low tide per day — because of the way different tidal signals interact.
Why Flood Timing Matters
As sea levels rise, coastal flooding is increasingly occurring even without storms, making an understanding of when floods are likely to occur increasingly important.
“This matters because timing influences impacts,” Haigh says. “The same flood can have very different consequences if it occurs during the morning commute, business hours or in the middle of the night. Understanding these temporal patterns could improve flood forecasting, emergency planning, infrastructure operations and long-term coastal adaptation
Knowing when coastal flooding is most likely to occur could help people, businesses and emergency managers better anticipate disruption and plan accordingly. That information could become even more useful as rising sea levels make it easier for tides and relatively small weather events to push water above flood thresholds.
“Higher mean sea levels signify that it will take only a relatively small weather contribution or sometimes simply a very high astronomical tide to cross a flood threshold,” Haigh says. “Understanding exactly when those critical tidal windows occur could therefore become an increasingly important component of coastal flood forecasting and preparedness.”
About the Researcher
Professor Ivan Haigh is a professor and eminent coastal and physical oceanographer. A coastal and physical oceanographer, he earned his bachelor’s degree in oceanography and mathematics, and his Ph.D. from the University of Southampton. He later served as a professor of sea level and coastal impacts at Southampton and directed its Center for Doctoral Training for Resilient Flood Futures. Haigh joined the University of Central Florida in 2025, as the director of the Center for Integrated Coastal Research.
