Sand Banks of the Atchafalaya Basin

 

Sand Banks of the Atchafalaya Basin

Why is sand needed to restore the coast spent filling the Atchafalaya Basin floodway?

Two weeks ago, GRN went out with Jody Meche of Crawfish Producers West to see how the crawfish-producing lakes of the Atchafalaya Basin have become hills. Instead of  muddy bayous, thick with trees, grit and sand chewed our prop in the shallow waters of Bayou Bristow and Bayou Brown, in the Bayou DesGlaises management area. In some places, feet of sand have filled in the basin relatively quickly. Crawfish traps lie buried under feet of new fill. 


Cypress grove of Bayou Des Glaises
Cypress Grove of Bayou Bristow (note: boat)

 

 

 

 

 

 

 

Filled Cypress Grove of Tin Can Lake, east of Billy Little's Lake (note: walkable)

Sand Banks of Tin Can Lake, east of Billy Little's Lake (note: cypress knees below bank line)

sand banks on work canal

Sandy Cut Banks along the 'work canal' running south from the I-10 canal, east of former Tin Can Lake

Instead of shallow water cradles of life, we saw new sand banks rise up to seven feet above the water. In some cases, the sand has filled basins inches per year. Five year old trees are buried under 5 inches of sand. In other places, the sand has risen feet per year. There's nothing to tell you that the area where you stand was once a crawfishing ground, save the white styrofoam floats that remain on the land above the buried traps.


Get the shovel! Maybe there's crawfish under that sand? 

A Normal Crawfish Trap, lain diagonally in shallow, flowing water

New cypress trees emerge from the new banks, but once the banks grow tall enough, trees are choked out by invasive vines and tallow. Deep water is needed to keep the cypress forests, but the water gets shallower until scrub-covered hills emerge.

South of Bayou Bristow, along Bayou Sorrel, this process has begun. Here, we can see changes in elevation from LIDAR data along oil and gas spoil banks. Energy Transfer Partners owns pipelines in the Florida Gas spoil area, as well as south in the 'Williams canal"--the proposed route of the Bayou Bridge Pipeline. These spoil banks slow the flow of sediment-laden waters from the Pilot channel, and fill in Lake Chicot and East Grand Lake.

It seems like a cruel joke, that sand that could be restoring our coast in Terrebonne parish is filling in crawfish and migratory bird habitat. But there are powerful people who want fishing grounds to silt in--that way, there are more trees to mulch.

There's sand in them hills! Great for building the coast, not great for deep swamps.

As we float west from Bayou DesGlaises to Bayou Brown, closer to the Pilot Channel, the swamp has gotten shallow enough that logging crews are able to move heavy equipment into the groves. There we see the final result of fill-- loggers have taken cypress trees three feet in diameter along with large willows. The fact that willow is being logged along with cypress is an indicator that these trees are destined to become mulch, rather than a lumber product. 

Freshly logged cypress trees, soon to become garden mulch. 

A logging road runs west to east, blocking the north to south bayou, west of Bayou Brown. Note the many dots --stumps-- throughout the photograph. 

Once this forest is lost, it is not likely to recover. Trees hundreds of years old take hundreds of years to recover--longer than the lifespan of any guarantee. To date, the sand filling the Atchafalaya Basin has been left out of coastal restoration plans. Although Louisiana DNR has made progress moving sand from the Basin, and toward the coast, there's so much more that needs to be done to preserve this river of trees. Atchafalaya Basinkeeper has proposed a plan [.kmz] to preserve the engineering capacity of the Floodway and the ecology of the Basin.  We hope that more people across the Gulf will consider it, and act to stop the silting of the Basin. Otherwise, we will only know what could have been, and the treasure we used to have. 

Scott Eustis is GRN Coastal Wetland Specialist

 

 

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