Jeff Masters Lake Okeechobee Nears Highest Water Level in 10 Years - good read
After Hurricane Irma dumped widespread rainfall amounts of 8 – 12” on September 10 – 12 over much of Florida, the Army Corps of Engineers is battling to draw down the level of Lake Okeechobee. The lake level has risen more than 2.5 feet since the hurricane departed, and will likely reach its highest level in ten years next week as flood waters from Irma’s rains continue to arrive. A new concern are rains of 1 – 4” expected this weekend from slow-moving tropical disturbance Invest 99L, currently over Cuba, which will bring additional inflows to the lake. Under ideal conditions--with no inflows into the lake--the Army Corps can only lower the lake level by about 0.4" per day. The lake level stood at 16.3’ above sea level on Thursday, well above the maximum 15.5’ level the Army Corps of Engineers tries to maintain in order to relieve pressure on the aging Herbert Hoover Dike that surrounds the lake. The current high-water levels do not present an immediate danger to the dike, but should another hurricane bring widespread rain amounts of 10+ inches to Florida sometime in the next month, there will be a significant danger of failure.
Lake Okeechobee’s one cubic mile of water represents an important source of fresh water to South Florida, but also poses a grave danger. The 143-mile long Herbert Hoover Dike surrounding the lake was built in the 1930s out of gravel, rock, limestone, sand, and shell using old engineering methods. The dike is tall enough that it cannot be overtopped by a storm surge from anything but an extreme hurricane, since it rises to a height of 25 feet above normal lake stage, which is 15 ft above mean sea level. Hurricane Irma’s winds and storm surge did only minor damage to it on September 10 - 11. However, the dike is vulnerable to leaking and failure when heavy rains bring high water levels to the lake. A 2011 risk assessment estimated the dike's probable failure rate at every fourteen years, and a 2008 Army Corp of Engineers study said this about the vulnerable dike:
According to palmbeachpost.com, in the wake of the hurricanes of 2004 and 2005, the Army Corp of Engineers embarked upon a $1.9 billion project to fortify the dike, which is now about half done. A 22-mile cutoff wall between Pahokee and Belle Glade has been completed, and many aging culverts around the lake’s 143-mile perimeter have been replaced. Still, the dike remains a Level 1 risk, considered by the corps to be the most likely to fail.
1928 hurricane in Florida
The shores of Lake Okeechobee are the site of the second deadliest natural disaster in U.S. history--the 1928 Okeechobee Hurricane. This mighty hurricane caused catastrophic damage where it struck the Florida coast as a Category 4 storm near Palm Beach, and weakened only slightly to Category 3 strength with 130 mph winds when it passed over Lake Okeechobee. The powerful winds of the hurricane brought a 12' storm surge to the south end of the lake, which overwhelmed the 6' high levees protecting the farm lands to the south. The resulting flood covered an area of hundreds of square miles with water up to 20' deep, and killed at least 2,500 people--mostly black migrant farm workers. A mass grave at the Port Mayaca Cemetery east of Port Mayaca contains the bodies of 1,600 victims of the hurricane. The Herbert Hoover Dike was built in the 1930s around most of Lake Okeechobee in response to this disaster.
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