Terrebonne Parish, Louisiana, got the name “good land” from French-speaking settlers – but the area is actually more water than land. All that water poses a serious threat to the 112,000 residents of the parish during storms. To protect themselves, they built a series of barge floodgates and use Xylem water monitoring technology to know when to open and close them.
“We have so many waterways, we’re so inundated with water, it’s part of life,” says Jason Kennedy, one of the founders of Delta Coast Consultants in Terrebonne's largest city, Houma, Louisiana. “It’s the reason people are here, come here, live here.”
Terrebonne Parish sits at the top of a 90-mile-long, shallow coastal shelf, Kennedy notes. When hurricanes spin up the Gulf of Mexico, the shelf builds storm energy into huge surges that slam into the parish and wash over the communities.
Flood control system uses barge gates
A flood control system for the area was approved in 2007 by the federal government but was never properly funded. The Morganza to the Gulf Hurricane Protection System now under construction includes 98 miles of levees. Floodgates manage canals, rivers and bayous that pass through the levees, while environmental gates permit flow to wetlands.
Even with tax revenues and the help of cost-share funds from the state, Terrebonne Parish has had to be innovative to afford its system, notes Reggie Dupre, Executive Director of the Terrebonne Levee and Conservation District. He leads the effort to see it through its construction.
Instead of building expensive sector floodgates, the levee district adopted a much more cost-effective approach called a barge gate. In the open position, a barge as long as the channel is wide sits on a platform, weighed down by a few feet of water in its hull. One side of the barge is attached to a piling that serves as a pivot, like the hinge on a door.
When a storm approaches, the gate crew empties the water to float the barge off of its platform, then reels in the loose end to shut it like a door across the channel. Once it fully blocks the channel, the crew fills its hull with water to sink it in place on a set of pins, forming a seal on the concrete floor of the channel. So far, the levee district has built 11 barge gates, each about one-third the cost of a sector gate.
Working with the tides to close the floodgates
Closing a barge gate is a delicate operation that requires a skilled crew and favorable conditions. Crews work with the tides to close the gates and need to keep a close eye on the ebb and flow of water.
Over the past three years, Delta Coast Consultants has been working with Xylem to install suites of monitoring instruments on both sides of its many barge gates. These stations provide all kinds of data on parameters like water level, water velocity, water flow and direction, and wind speed and direction. These data are transmitted every six minutes to the levy district’s command center.
“Some of the gates take as many as six people to operate, and they can take an hour and a half to close, as opposed to three minutes for a sector gate,” he explains. “You have 18 operations employees trying to operate 13 flood gates across 60 miles. So this technology becomes very, very important to understanding what's going on and how it affects where you want to send your employees. Without this YSI system, we'd need double the amount of employees, which we can’t afford.”
By the start of the 2019 hurricane season, ten of the parish’s 13 floodgates had Nile WaterLOG radar stage sensors; SonTek-SL (side-looking) velocity, level and flow meters; RM Young wind sensors; rain gauges and dataloggers. Close monitoring in real time has allowed the levee district team to see the dramatic effects of landscape, wind, and tide on surges across the parish.
Up-to-date data for residents and pilots
It didn’t take long for residents of Terrebonne Parish who rely on the waterways – the shrimpers and oystermen, the barge haulers, the recreational fishing enthusiasts – to ask for access to the data streaming into the levee district’s system.
The district commissioned a public app, then switched to an online service at www.tlcd.org/mobile.
Visitors can click on any of the floodgates that have instruments and get an instant, up-to-date look at flood-side stage, wind direction and wind speed, and the status of the gate. Those who subscribe by sharing their emails and cell numbers can get alerts when the gates are closing or opening.
Kennedy says pilots on the system can use the website and alerts to adjust their routes on the Gulf Intracoastal Waterway and other channels based on gate closures – decisions that can keep them working during changes in the weather or get them home safely as storms close in. News on the gates also allows them to get back to work after storms blow through.
“Everybody wants to know not only when it’s going to close, but when it’s going to open,” Kennedy notes. “We don't want to keep things closed any longer than we have to. There’s so much commercial interest in getting out to the water.”
Written by: Steve Werblow