A breach of the Herbert Hoover Dike would almost certainly rank as a catastrophe — but the scope and scale of loss would vary widely depending on where and when it burst and how much water was in Lake Okeechobee.
If the worst did happen, the U.S. Army Corps of Engineers, regional emergency managers and local leaders hope they have taken steps to — at the very least — minimize the death toll.
“I would like to hope and pray that it’s not as much a life safety issue anymore,’’ said longtime Palm Beach County Administrator Robert Weisman.
After Hurricane Katrina overwhelmed the protective levees surrounding New Orleans and killed some 1,800 people in 2005, South Florida emergency managers for the first time drew up mass evacuation plans for towns that suffered deadly flooding from Lake Okeechobee during hurricanes in 1926 and 1928. The Corps, meanwhile, says it has strengthened the dike’s most vulnerable 21-mile stretch.
But at high water levels, the dike remains a high-risk hazard for potentially devastating flooding. A major failure could send torrents through lakeside towns and muddy water to the suburban outskirts of Palm Beach County.
‘So many variables’
Corps spokesman John Campbell said it’s difficult to predict what might happen. “There are just so many variables,’’ he said. “A lake at 17 feet is going to be very different than a lake at 20 feet. Certainly, the higher the lake level, the more that would actually be felt.’’
A hurricane battering embankments or pushing the lake over the levee could also multiply the threats.
A Corps-funded simulation of breaches presented at a 2011 national dam safety conference mapped out huge swaths of lakeside land vulnerable to flooding. The simulation underlined what history has already shown. The biggest threats and impacts would come along the southern bank, where the dike protects 40,000 residents living along the lake’s most populated stretch from Clewiston to Pahokee.
In an extreme worst-case failure, the simulation extended flood waters more than 20 miles, spreading south and east across an expanse dominated by sugar farms. The deepest pools would collect in areas that have subsided by several feet after decades of farming on eroding peat soils that were once Everglades marsh. Much of the area is still farmed but homes and apartments also have been built in some of the lowest-lying areas near the lake.
The modeling suggests elevated roads, railroad tracks and levees would help contain much of the water as it neared western Palm Beach County’s suburbs.
The presentation included maps only for a breach at 25 feet. That’s far above the historic high of 18.8 feet and the 21-foot level where engineers predict the existing levee would fail.
While federal engineers openly discuss dike deficiencies the Corps remains reluctant to provide details, maps or modeling of the potential consequences of a failure, citing security concerns heightened since the 9/11 terrorist attack.
“We try and balance the risk of making sure the public is informed, and keeping the public safe with operational security of not allowing others to know what our vulnerabilities are,” said Laureen Borochaner, engineering division chief of the Corps’ Jacksonville office, which monitors and maintains the dike.