OKEECHOBEE -- Hurricane Dorian could cause Lake Okeechobee to rise as much as 3.5 feet over the next month, as water from the Kissimmee basin drains south. In a Friday telephone conference, Col. Andrew Kelly, commander of the U.S. Army Corps of Engineers Jacksonville District, said the lake level is 13.66 feet today (Aug. 30). While the risk of a breach to the dike is low at this point, the real concern could come later in the season, if the lake is already at 17 feet when another tropical storm hits.
The dike is in better shape than it was two years ago when Hurricane Irma hit, Col. Kelly said. Some construction projects that were areas of concern in 2017 have been completed. The most vulnerable area of the dike now is the northwest section, near Lakeport, he said.
“The northwest side of the dike probably has the most risk associated with it,” he said. If a category 4 hurricane crosses the Herbert Hoover Dike, there could be localized flooding, he said, but he does not anticipate a breach.
“We don’t anticipate any overtopping or breaching of the dike during the storm,” he explained. The risk will be greater after the storm passes, when the vast floodplain north of the big lake will drain south into the Kissimmee River and the canals that flow into Lake Okeechobee.
According to the U.S. Geological Services, before the Kissimmee River was channelized and the flood control canals were dug, rain that fell in the upper Kissimmee basin slowly sheetflowed south into the lake, taking six months or longer to reach the big lake. Now, the area drains very quickly, rapidly pushing water into the confines of the earthen dike.
Col. Kelly said the corps had teams of inspectors on the dike this week. He said as soon as the storm passes, the corps inspectors will be out on the dike checking for any problem areas. Rocks of varying sizes that can be used to reinforce any weak areas are already stockpiled around the dike.
After the hurricane passes, Col. Kelly said they anticipate heavy releases to the St. Lucie and Caloosahatchee estuaries to slow the rise of the lake. He said they will not start lake releases until local area flooding in the areas around the estuaries has subsided.
Col. Kelly said no water was released to the coastal estuaries in anticipation of the storm because there was not sufficient time for such releases to make a difference in the lake level. In addition, no water can flow east unless the level of the St. Lucie canal is lower than the lake level. The St. Lucie canal is usually maintained between 14 and 14.5 feet above sea level. Over the past seven days, water from the C-44 canal was released at the St. Lucie lock at an average of 292 cubic feet per second. All of the water released through the St. Lucie Lock since March has been local basin runoff.
No water has been released to the Caloosahatchee since the start of the rainy season because the river had sufficient flow from local basin runoff. Over the past 7 days, the average flow at the Franklin Lock was 3,587 cfs, all from local basin runoff. Flows above 2,800 cfs are potentially harmful to the estuary because heavy flows lower the salinity levels. Flows lower than 450 cfs allow salt water intrusion in the river. During the dry season, water was released from the lake to the river to prevent saltwater intrusion.
Col. Kelly said the corps will consider water quality and flooding conditions before starting lake releases after the storm passes.