Lake O hits highest level since 2005, raising concerns its dike could fail

Rainfall from Hurricane Irma has pushed the water level in Lake Okeechobee to its highest point since 2005. Now, with more wet weather in the forecast, nearby residents fear a collapse of the 80-year-old dike around the lake.

As a result, the U.S. Army Corps of Engineers is dumping large volumes of lake water out into coastal estuaries — exactly as it did last year, when those releases caused a massive toxic algae bloom that closed Atlantic coast beaches over the Fourth of July weekend.

RELATED: Irma roughs up endangered snail kites, birds that help us gauge the Everglades' health

Meanwhile, Corps officials have stepped up inspections of the dike to three to four times a week to make sure its continuing leaks don't grow to the point of endangering people living near it.

"We recognize that as the water level continues to rise, there is an increased risk of failure," Corps spokesman John Campbell said.

The dike around the lake is classified as one of the most vulnerable in the nation. The earthen embankment on the south end of the lake is older, and thus more in danger of being breached, he said.

That puts the communities south of the lake — Pahokee, Belle Glade, South Bay and Clewiston among them — at the greater risk for both property damage and loss of life.

"If the dike fails, it would be catastrophic for our communities," a south-of-the-lake group called the Everglades Agricultural Area Farmers said in a news release this week.

As of Tuesday, the lake had hit 16.56 feet, exceeding last year's high of 16.4. That put it at the highest level since Hurricane Wilma hit 12 years ago, when it topped 17 feet. By Wednesday it had crept up to 16.67 feet.

"The rate of rise has accelerated," Campbell said Thursday.

By Friday, it hit 16.83 feet.

The lake's highest recorded level was nearly 18½ feet in 1947, the result of an unnamed Category 4 hurricane that slammed into Fort Lauderdale.

Lake water has for years slowly seeped through the earthen embankment. But once the water level reaches a certain point, the pressure inside the dike begins forcing even more water out at the bottom, often carrying sand and debris with it, a dangerous situation.

"Any time we get above 17½ or 18 feet, we have seen issues with increased seepage," Campbell said.

That's why the Corps has to step up its inspections, to watch for any sign of a breach.

"The seepage can cause a weak spot and it could cause a chain reaction that could cause a collapse of the dike," explained Tommy Strowd, an engineer who held a variety of top positions at the South Florida Water Management District from 1996 to 2014.

The situation get worse if the winds from a tropical storm or hurricane whip up waves on the lake too, Strowd said.

"As the water storage in the lake gets higher and then the wind comes, then you've got a problem where it sloshes, and those sloshes can chew into the walls of the dike," he said.

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So take a 17 feet or more lake level that's pushing seepage through the bottom of the embankment, add a wind-driven storm surge that damages and overtops the embankment, he said, "then you're really in trouble."

The Corps has been trying to lower the lake level over the past month, but it's been hampered by weather events beyond its control, Campbell said. Hurricane Maria pushed higher tides into the St. Lucie River so the releases couldn't go out as fast. Meanwhile, the Corps had to time its releases into the Caloosahatchee and St. Lucie rivers so as not to worsen the flooding already occurring along those waterways.

Until the 1920s, Lake Okeechobee overflowed regularly — and naturally. Rain south of Orlando would swell the twisting Kissimmee River, which fed the lake. When the lake overflowed, it would send water rolling into the Everglades, forming the River of Grass, which would flow in a vast, shallow sheet all the way down to Florida Bay.

But ranchers persuaded the Corps of Engineers to straighten the Kissimmee so they could have bigger, drier pastures. That sent more polluted water shooting into the lake. To attract settlers to the lake, the state also built a pair of canals that turned the St. Lucie and the Caloosahatchee into drains for the lake's bathtub.

A 1928 hurricane caused the lake to overflow, killing thousands, an event that inspired the climax of Zora Neale Hurston's classic novel Their Eyes Were Watching God. President Herbert Hoover ordered a dike built around the lake to ensure it never happened again — although that cut off the flow of water for the Everglades. The dike construction did not include a spillway to dump out excess water automatically.

With the River of Grass sequestered at its source, developers moved in, carving out space for homes and stores and offices and schools from the drying muck. The Everglades as it exists today is half the size of the original.

Meanwhile, whenever heavy rains hit South Florida, the water in Lake Okeechobee has nowhere to go other than up. When that happens, the Corps opens its floodgates to send millions of gallons to the east and west.

Over the years, those releases of lake water have repeatedly led to toxic algae blooms and other woes in the estuaries attached to the Caloosahatchee and St. Lucie rivers. In 1998, for instance, mullet in the St. Lucie were found with half their flesh eaten away.

The releases have become an environmental and economic disaster for the fishing and tourism industries in both places, particularly with last year's toxic algae bloom. So far this year no bloom has been spotted in the lake, Campbell said.

"We all share a desire for a flood protection system that would be more environmentally friendly than the one we have now," Campbell said. "The system we have does have some flaws in terms of its environmental impact — but it does a great job of flood protection."

Contact Craig Pittman at craig@tampabay.com. Follow @craigtimes.