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Nov

11

2015

From The Blog

Historic Weather Event Brings Unprecedented Rain, Flooding to Kiawah

During a four-day span from Oct. 2 – 5, the Lowcountry experienced a truly historic weather event. An unusual combination of weather conditions led to steady, heavy rain over the area, dropping over 18 inches of rain on Kiawah Island alone and more than 26 inches of rain in other Charleston areas.

Unpredictable and Unexpected
Based on historical data and statistics, meteorologists initially dubbed this system a “one-in-1,000-year weather event” though even that turned out to be an underestimation. Rainfall totals as high as what were seen with this system were considered so improbable that forecasters and analysts couldn’t even calculate odds that long.

“It’s incredible,” said Sanja Perica, director of the National Oceanic and Atmospheric Administration’s Hydro meteorological Design Studies Center, which studies rainfall probabilities. “We don’t recommended extrapolating(rainfall probabilities) beyond 1,000 years, but if we did, oh my goodness.”

The National Weather Service, Charleston, on Thursday (Oct.1) warned of historic rainfall through Sunday (Oct. 4), but predicted less than half of the amount that fell in many areas.  Meteorologist John Quagliariello said forecasts correctly advised flash flooding, and predicted rainfall totals climbed as the storm closed in.

“It’s almost impossible, especially a couple of days out, to forecast an extreme event,” he said. “I don’t think you would ever see any office forecast 20 inches or more.” By Monday afternoon (Oct.  5), nearly 27 inches had fallen in Mount Pleasant, where the highest total was recorded near Boone Hall. Estimates suggest rainfall totals in the Lowcountry were approximately twice what the area experienced during

Hurricane Hugo in 1989. A so-called 1,000-year rain event has a one-tenth of 1 percent (0.001 percent) chance of happening in any year, which works out to once every 1,000 years. The heaviest rain that fell Friday through Sunday across a wide swath of the state, roughly from Mount Pleasant and Awendaw to Columbia, was a one-inmany-thousands event with more than two feet of water falling from the sky in 72 hours.

Combined with unusually high tides that were occurring during that same time frame, widespread flooding was seen throughout the Lowcountry. Many areas are still recovering from this unprecedented event.

Impact on Kiawah
Much like the rest of the Lowcountry, Kiawah Island experienced unprecedented rain totals, receiving over 18 inches of rain. When combined with the unusually high tides, the island saw significant flooding in certain areas. “In the week leading up to the storm, news reports were focused on the “blood moon” and associated high tides, along with trying to predict the path of Hurricane Joaquin. It was not until Thursday (Oct. 1) that the weather service predicted historic rainfall, and even then they predicted half of what we received,” said KICA Chief Operating Officer (COO) Jimmy Bailey. “Our drainage systems are well engineered, but it’s just not possible to quickly expel that much water. Once the rain stopped, our system did its job and the island was drained in about a day.

Unfortunately as was seen throughout the state, the amount of rain was more than anyone expected, and flooding occurred.” Following the storm, KICA began assessing damage and putting a plan in place to repair damage. However, it also began a process to determine if there are lessons to be learned for the future. As part of that, it reviewed the actions undertaken by staff in advance of the storm and while the event was underway. A full debrief will be performed with various entities, and part of it will focus on the timeline of events and actions taken. Throughout the entire event, KICA Security and various other employees were on Kiawah.

A Day-by-Day Look at the Storm
Wednesday, Sept. 30
A dam that had been constructed on Canvasback Pond was removed. It had been installed to allow a drainage pipe under Glen Abbey to be replaced, but it was causing upstream pond levels to rise.

Friday, Oct. 2
All floodgates were set to prevent water from flowing into the system, but to allow water to flow out on the falling tide. Because of the unusual high tide cycle on Kiawah at that time (2.5-3 feet above normal), the amount of time in the tide cycle for water to flow out of the ponds was reduced significantly. In several locations, high tides over-topped the outfalls and water was flowing on to the island from the marsh. In addition to tides being unusually high, the wind direction was blowing the tides ashore.

Also on Oct. 2, pumps were positioned on the upstream side of Glen Abbey to move 225,000 gallons-per-hour downstream in an attempt to relieve upstream pressure.

Saturday, Oct. 3
Flooding all over the Lowcountry, including Kiawah. Access to and from the city of Charleston was completely closed to vehicular traffic. KICA COO was forced to access the island by boat. Large sections of the Kiawah Island Parkway and Governor’s Drive were flooded all the way to Blue Heron Pond Road.

KICA Security, Charleston County Sheriff’s Department and St. Johns Fire District were performing a number of water rescues from vehicles that stalled in the floodwaters.

KICA provided a standby boat and captain to emergency personnel in the event that it was needed.

Vanderhorst Gate flooded and staff evacuated. Rainfall intensified Saturday afternoon/evening.

Sunday, Oct. 4
At 6 a.m. Sunday morning, Lakes staff discovered that someone had tampered with one of the floodgates at Canvasback Pond and closed it. It was estimated that the gate was closed for five-to-six hours.

A sinkhole developed on Bohicket Road, limiting access to and from Kiawah Island to River Road.

Numerous vehicles continued to try and pass through floodwaters; water rescues continued.

KICA convened staff via teleconference, and among other issues, began working with Sysco to plan a large food delivery to the island for those who remained stuck in homes.

In coordination with the Town of Kiawah Island, a decision was made to restrict commercial traffic on the island on Monday, Oct. 5.

Monday, Oct. 5
Rain finally stopped, but flooding remained heavy. At low tide, water was rushing off the island. TOKI, KICA, and SJFD jointly concluded that several roads must be completely shut down. Roads remained closed for approximately five hours.

With rain stopped, the decision was made to move one of the pumps being used at Glen Abbey to the V-Gate to increase drainage at this critical intersection.

By 9:45 p.m. Monday night, all roads were deemed passable. It took two low tide cycles after the rain stopped to completely drain the island from this historic rain event.

On the Road to Recovery
With the rains ended and flooding subsided, Kiawah and the rest of the Lowcountry have turned their focus to recovery. The KICA board met on Tuesday, Oct. 6 and approved $265,000 in recovery funding. Numerous restoration efforts have been completed or are underway.

KICA Land and Lakes Management personnel continue working to replace damaged landscaping, clean up debris, remove dangerous trees and branches, and more. A street sweeping service has been working nights to clean mud and debris from island roadways, and KICA Major Repairs staff have been hard at work repairing damaged boardwalks, walk bridges and leisure trails, and assessing drainage issues. The Livability Department has been assisting part-time resident members who are seeking information on their homes by doing an exterior visual check of the home for flooding or downed trees, then returning information to the member. Finally, Security staff members have been on the island 24/7 since the event began, ensuring member safety, while the Communications Department has coordinated constant news alerts and social media posts to keep members informed during and following the event.

“The tireless efforts and dedication of our entire staff is to be commended,” said Bailey. “Our staff continues to work around the clock to not only ensure a full recovery of the island, but to learn from this event and prepare in case something like this happens again.”

For more information and updates on island recovery following this historic event, visit kica.us/storm-recovery.