Herbert Hoover Dike protects much of South Florida

The safety of the Herbert Hoover Dike is vital to the people of the Glades. Those who live around the Big O’s southern shores in South Bay, Belle Glade, Moore Haven and Clewiston know the danger they could be in if the dike failed. The dike also protects the farms of the Everglades Agricultural Area (EAA), the Everglades and more.

At the December public hearing on the South Florida Water Management District’s proposal for the EAA reservoir, Clewiston Mayor Mali Gardner was among those who reminded officials that some Floridians don’t understand the importance of the dike.

“The reason why we are here, whether it was back in 2008 when we heard ‘take the land’ and now this past year ‘flood the communities’ and ‘remove the levee.’ The job that we all have to do is very difficult,” said Mali Gardner, mayor of Clewiston. “When you hear comments of ‘take the land,’ and ‘flood their towns,’ those are incendiary comments. And when we know there are underlying forces that do want to see agriculture taken out of the EAA, and people who do want to see our towns decimated, we are going to stand up. We are going to speak.”

Those who live in the shadow of the dike have been outspoken about the importance of the rehabilitation measures to ensure its safety. But the safety of the Herbert Hoover Dike affects everyone in South Florida. If the dike should fail, it’s not just the rural towns and EAA farms at risk — much of South Florida could be impacted.

The amount of water in the lake is mind-boggling. Just one inch of water on the 730-square-mile surface of Lake Okeechobee equals 12 billion gallons. The higher the lake level, the more water pressure is pushing against the earthen dike.

The U.S. Army Corps of Engineers tries to keep the lake between 12.5 and 15.5 feet above sea level, considered the best range for the lake’s own ecology and the safest range for the dike. The actual depth of the lake varies.

Consider the elevations of the land surrounding the dike. The City of Okeechobee, at 26 ft. above sea level, is at low risk of flooding. Those on the east, west and south sides of the dike are at lower elevation and higher risk of flooding, with Clewiston and Belle Glade at 16 ft. above sea level and Moore Haven and Pahokee at 13 ft. Further south, the elevations are lower, with Miami just 6.5 ft. above sea level.

Another consideration is the impact of high water levels on the East Coast Protection Levee. This levee, another earthen dam, runs 105 miles from West Palm Beach to the Tamiami Trail. It serves as a buffer between three Everglades Water Conservation Areas and portions of the most populated regions in South Florida. In 2017, concerns over high water levels in the water conservation areas caused the U.S. Army Corps of Engineers and SFWMD to back-pump billions of gallons of water from these conservation areas into Lake Okeechobee. The reasons for this extreme measure included the safety of Everglades wildlife and the protection of the East Coast Protection Levee. Just like the Herbert Hoover Dike, the higher the water levels rise, the greater the risk to the dam.

Should the dike fail, the unrestricted flow of nutrient-rich water would also impact the Everglades. The phosphorus levels in the lake’s water varies. It averages around 120 parts per billion of phosphorus. During periods of high water, the phosphorus level goes up. It also goes up if the lake is churned by a storm.

The Florida Department of Environment Protection set the maximum phosphorus level for the Everglades at 10 ppb. A system of water conservation areas and water treatment areas is used to reduce the nutrient levels in the water before it goes into Everglades National Park. If the dike failed, the rush of nutrient-rich water from the lake wouldn’t stop for treatment in the water conservation areas.

In 2008, the Florida Department of Emergency Management imagined a potential scenario, modeled on their estimate of what would happen if the Herbert Hoover Dike breached during a Category 5 Hurricane.

For the purposes of the hurricane preparedness exercise, they modeled the following: A Category 5 hurricane makes landfall just north of Fort Lauderdale. The storm travels northwestward across the state, maintaining Category 4 strength as it touches the southwest reaches of Lake Okeechobee.

The emergency scenario imagines:

Heavy rains cause the water levels on the lake to rise. A breach to the Herbert Hoover Dike near Clewiston. Tornadoes spawned by the hurricane also touch down on the dike, causing two more breaches, near towns Pahokee and Belle Glade.

The lake begins to flood the surrounding communities. Eventually, much of South Florida will be inundated.

U.S. 441 and 98, and State Roads 715 and 80 are destroyed by the slow-moving water.

The wall of water spreads out from Lake Okeechobee toward the Atlantic Ocean. It will be weeks before the flood waters recede.

The East Coast Protection Levy can’t stop the pressure of billions of gallons of water from the lake.

The lower elevations south of the lake mean the billions of gallons contained in the 730 square mile lake flow – as water does – downhill.

Evacuations began in heavily populated Broward, Miami-Dade and Palm Beach counties. But there isn’t enough time.

After the dike breaches, more than 640,000 evacuees in Broward have less than 14 hours to move. Miami-Dade’s more than 936,000 evacuees have less than 13 hours to get out. In Palm Beach County, nearly half a million people have less than 16 hours to leave.

Roads are flooded. The people can’t get out in time and are trapped by rising floodwaters.

Nearly 3 million Floridians try to evacuate low lying areas.

In Miami-Dade County, the floodwater puts 212 miles of evacuation routes under 2 feet or more of water. In Palm Beach County, 180 miles of flooded roadways make it impossible for residents to flee.

The death toll rises and damages to homes and businesses is in the hundreds of billions of dollars.

The environmental damage to the Everglades is devastating.

The flood will have a longterm impact on businesses, families and the Everglades. The hurricane winds have churned the lake, mixing the muck from the bottom through the water column. As that muddy water flows out of the lake, it destroys decades of work to reduce the phosphorus loads in water entering the Everglades. It will take decades for the Everglades to recover … if it ever can.

The 2008 hurricane model estimates business interruption losses over $53.5 billion.

The good news: It was only an exercise.

In addition, the Herbert Hoover Dike is in better shape than it was ten years ago. Work has also been done to improve the safety of the East Coast Protection Levee.

Since 2001, the corps has made a significant investment, over $870 million, in projects designed to reduce the risk of catastrophic failure of the aging structure. Actions taken include installing a partial cutoff wall along the southeast part of the dike, removing and replacing water control structures (culverts), and conducting a variety of studies and technical reviews to help ensure the safety of south Florida residents.

The current schedule, with the dike repairs funded by the federal government, calls for repairs to be completed by 2025. In 2017, the Florida Legislature and Gov. Rick Scott approved a plan to use state funding to speed up dike repairs by three years.

Publisher Katrina Elsken can be reached at kelsken@newszap.com

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