GulfNet RTK measuring levee heights

A new technological system for measuring the heights of hurricane protection system levees in south Louisiana was discussed by LSU engineering professor Roy Dokka in a presentation given Friday in Houma.

The system, GulfNet Real Time Kinematic, uses the Global Positioning System to measure levee elevations each second. Information is gathered at 42 GPS Reference Stations in south Louisiana – including ones in Thibodaux, Houma and Morgan City – and transmitted to LSU. The data is collated and sent to the National Oceanic and Atmospheric Administration.

GulfNet RTK, which was funded by the Federal Emergency Management Agency, has been in place for around two months.

“A system of accurate elevations has been nearly impossible to maintain,” Dokka said. “We’ve never known what the elevations were.”

He said the former measurement system, LIDAR, overestimated the height of levees, resulting in inaccurate flood maps.

“Now we have a quick, accurate way to know, to fix it,” Dokka said. “If you don’t know, you can’t fix it. This is the first time we’re measuring it correctly.”

In 2001, the federal government told Louisiana the state was planning levees blind, he said. NOAA called the measurements inaccurate, obsolete and unable to support public safety.

The height of many levees in south Louisiana decreases because the land underneath subsides. Dokka said the subsidence derives from the smaller amount of fresh water south Louisiana receives from its leveed rivers and the encroaching salt water of the Gulf.

The sinking is not caused by drawing oil from underneath the land, as is sometimes believed.

GulfNet RTK tracks the subsidence.

For instance, the Louisiana Universities Marine Consortium in Cocodrie has had a GPS station for five years. Data from the station indicates the LUMCON building is sinking a quarter inch annually.

“Cocodrie is slowly going down,” Dokka said. “The Gulf is creeping closer to Houma.”

Dokka said the more accurate information compiled by GulfNet RTK will help Louisiana receive funding for Morganza-to-the-Gulf, the federal program authorizing funds to build hurricane protection levees in Terrebonne Parish for the first time.

“You’re going to get your levee,” he said. “This will (tell) people in Baton Rouge and Washington that this area is critical and Morganza-to-the-Gulf needs to be funded. You’ve got to have a levee between you and the Gulf.”

Dokka called Houma “the most vulnerable city on the Gulf Coast.”