Florida cities grew and grew. Then came the massive loss of protective coastline tidal flats

FORT LAUDERDALE, Fla. —A “coastal squeeze” has been plaguing some stretches of Florida and other parts of the U.S., as communities for decades expanded with development and vital tidal flats sustained irreversible damage, according to a newly released study.

The big-picture analysis by the Florida Atlantic University — which examined data from annual maps from 1985 to 2015 — revealed how urban expansion has considerably affected stretches of the Atlantic Coast and the Gulf, among other coastlines in the U.S.

In Florida, the cities of Jacksonville, Palm Bay, Fort Myers and Tampa were among the communities whose tidal flats were considerably affected, the study showed. “Findings from our study provide important implications for coastal land use and planning to sustain tidal flats,” Weibo Liu, one of the researchers, said in a statement. “Our study provides worthwhile data for scientists and lawmakers alike that will contribute to helping to develop policy and programs that address how massive urban expansion has tremendously undermined the environment of tidal flats along the U.S. coast.”

These tidal flats — or the muddy, marshy land that receive sediment deposits from bodies of water — can be an important asset, helping subdue storm surge. “Tidal flats are rich in sediments and mud, which greatly damps the destructive powers from the ocean, including tidal currents, waves, tsunamis and hurricanes,” the study says. The tidal flats may oscillate between being exposed or hidden by water, depending on tides.

“This is a transitional area between the totally dry land and permanently inundated ocean,” said Chao Xu, one of the primary researchers for the study. “Tidal flats can be a large region, like a swamp or coastal wetland. It can be really wide.”

Researchers from Florida Atlantic University sought to better understand the impact of urbanization on tidal flats across the United States. Results revealed human actions are to blame for tidal flat degradation, rather than natural factors.

Urban expansion skyrocketed during the 30-year study period, especially along the Atlantic coast, researchers found.

However, development in some cities was not found to overlap with tidal flat erosion, with Miami being one of them. Part of this is because the studied research period began in 1985, when places such as Miami and Tampa Bay were already quite urbanized and tidal flats had already diminished because of it, Xu said.

Tidal flats surround Florida’s perimeter, and while Miami was not found to be a primary culprit in creating tidal flat erosion, development and population growth are not slowing down any time soon, with more than 1,000 people moving to the state every day.

The research did find tidal flat erosion in Jacksonville, Fort Myers and Pensacola within the studied time period, primarily due to what Xu called “artificial surfaces,” which could be roads, residential homes, high-rise buildings, condominiums or transportation networks.

Xu, who is now an assistant professor in the department of geosciences at Texas Tech, said one of the prominent examples of tidal flats in Florida can be found in the Everglades. If development in the greater Miami area, which included everywhere from southern Miami to West Palm Beach, were to continue westward, then there might be more danger for tidal flats in the area, Xu said.

In similar research from last year, FAU scientists emphasized the importance of tidal flats to coastlines, calling them “the guardians for beachfront communities as they can largely mitigate destructive forces from the ocean.”

Areas without them are at greater risk of storm-related flooding and damage, Xu said.

“With the absence of tidal flats, beachfront communities demonstrate greater vulnerabilities against not only hurricanes but also coastal flooding,” he said.

Greater Miami residents should consider themselves fortunate that hurricanes have, for the most part, dodged the region in recent years because the area is very vulnerable, he said.

Xu said limiting groundwater extraction and managing waste are crucial to prevent against even further tidal flat damage.

Researchers urge local officials to make sure water channels remain unobstructed because otherwise the movement of sediment may be hindered. They also call for leaving space to allow for tidal flat migration.