Hurricane Irma was a “150 year event,” according to an assessment released Wednesday by the Villages District Office.
On-site estimates indicate that 12 to 15 inches of rainfall was received in a period of about 12 to 18 hours.
“It was an unprecedented rainfall event,” according to an assessment released at the weekly Welcome Wednesday event at the District Office.
The design storm for the water retention system in The Villages, as required by the water management district, is for a 100-year, 24-hour event.
The 100-year, 24-hour event for this area is 10.0 inches of rainfall. A “100-year event” is an event that has a 1 percent chance of occurring in any given year. This area received something like a 150-year event, which significantly exceeds the design capacity of the storm water retention system.
“Prior to Hurricane Irma, the region had received much higher than average rainfall, so the storm water retention systems, wetlands and lakes were higher than normal,” according to the assessment.
The excess rainfall (amount above average) received from June through August was approximately 11 inches.
If and when a design storm is experienced, the basins will rise to a flood level, which includes inundation of the golf courses that will temporarily render the courses unplayable while the flood waters are receding, according to the District.
“In all but the oldest areas of The Villages, the storm water retention systems responded wonderfully, and very few, if any, areas had impacts to structures from the rising water levels,” according to the assessment.
The oldest areas of The Villages that were constructed in the early 1970’s were designed to the storm water retention standards that were in place at the time. These standards did not include retention of runoff from a 100-year, 24-hour storm, so the retention systems in the oldest areas are not as extensive.
“Excess storm water has receded primarily as the result of infiltration. As the water level comes up, water spreads out, so there is greater surface area for infiltration,” the assessment said.
In addition, The Villages has an extensive water management and pumping system. Where available, water is moved from higher areas to areas with available storage, and irrigation systems are used to pull water out of the basins and spray it out on golf courses, roadways and other commercial areas.
“In specific parts of the oldest areas of the community, surface pumps are being utilized to remove flood waters from inundated areas to areas with available storage that also have pump stations that can disperse the excess storm water onto golf courses. The vast majority of areas are already back to normal, many areas will be back to normal within a relatively short time period, and some of the oldest areas may take a longer time period for full recovery,” the District said in its assessment.