Northwest Barataria Basin Freshwater Diversion Survey

Louisiana Department of Natural Resources

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Louisiana is losing land at an alarming rate, some 25 square miles of coastline a year. That’s equivalent to a football-field-sized slice of Louisiana disappearing every 30 minutes. There are lots of complicated environmental reasons for this, but a big one is the death of our freshwater swamps.

Because of the levee system, these swamps are starving for freshwater, and as the water becomes more brackish the swamps turn to marshes and then to salt-water marshes, and ultimately to open water.

The Department of Natural Resources is attempting to restore and maintain the cypress-tupelo swamp in one of these areas--the upper Barataria Basin—by installing a siphon on the Mississippi River. But before it did, it needed to create a model of the watershed to determine where to best put the siphon, which in turn required an accurate survey. ABMB took on the challenge.

And a challenge it was. The project called for determining the location of swamp elevations along a variety of project grids, the location and elevation of a highway bridge and associated culverts, as well as overbank surveys, channel cross sections, and average swamp elevations.

As project manager Steve Melton points out, “No one in Louisiana had done such a large survey in such conditions. We had originally thought we would use GPS Real-time Kinematic surveying methods, but the closed canopy made it impossible.” 

Instead, ABMB relied on a combination of Real Time Differential GPS and conventional leveling techniques, backed by GPS Real-time Kinematic methods to determine the elevations of 14 water staff gauges where there was a good GPS signal.

“We weren’t initially sure what combination of survey techniques to use,” notes Melton, “but we worked very hard to find the right techniques to get the job done accurately and in the allotted time.”

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