It wasn't that long ago much of Palm Beach County was under water restrictions.
Dr. Jeff Masters · September 28, 2017, 7:21 PM EDT
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 dike is old and frail
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 - 30 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:
"There is limited potential for a dike failure with lake levels as low as 18.5 feet. The likelihood of a failure increases at higher lake levels. At a lake level of 21 feet--a 1-in-100-year flood event--a dike failure would be likely at one or more locations. In the event of a dike failure, waters from Lake Okeechobee would pass through the breach--uncontrollably--and flood adjacent land. Flooding would be severe and warning time would be limited. And with 40,000 people living in the communities protected by the Herbert Hoover Dike, the potential for human suffering and loss of life is significant. Our engineering studies indicate the southern and eastern portions of the dike system are more likely to fail than the northern and western portions of the dike. In general, we would expect a warning time of 24 to 48 hours prior to a dike failure that releases water from the lake; however, under some conditions the warning time might be longer, and under others, a dike failure could occur with no warning." Belle Glade (population 18,000) on the southeast shore of the lake, is 16' above sea level, so if Lake Okeechobee is at 21' above mean sea level and the dike fails, 4 - 5 feet of water could inundate the town.
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.
https://www.wunderground.com/cat6/lake-okeechobee-nears-highest-water-level-10-years
Dr. Jeff Masters · September 28, 2017, 7:21 PM EDT
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 dike is old and frail
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 - 30 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:
"There is limited potential for a dike failure with lake levels as low as 18.5 feet. The likelihood of a failure increases at higher lake levels. At a lake level of 21 feet--a 1-in-100-year flood event--a dike failure would be likely at one or more locations. In the event of a dike failure, waters from Lake Okeechobee would pass through the breach--uncontrollably--and flood adjacent land. Flooding would be severe and warning time would be limited. And with 40,000 people living in the communities protected by the Herbert Hoover Dike, the potential for human suffering and loss of life is significant. Our engineering studies indicate the southern and eastern portions of the dike system are more likely to fail than the northern and western portions of the dike. In general, we would expect a warning time of 24 to 48 hours prior to a dike failure that releases water from the lake; however, under some conditions the warning time might be longer, and under others, a dike failure could occur with no warning." Belle Glade (population 18,000) on the southeast shore of the lake, is 16' above sea level, so if Lake Okeechobee is at 21' above mean sea level and the dike fails, 4 - 5 feet of water could inundate the town.
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.
https://www.wunderground.com/cat6/lake-okeechobee-nears-highest-water-level-10-years
