Audubon mini dredge: Building land at Rainey, one acre at a time
January 24, 2012 | Posted by Kevin Chandler in Restoration Projects

By Kevin Chandler, Mississippi River Delta Restoration Campaign

Louisiana coastal restoration often seems like a distant process – a product of reports and large-scale projects. And while reconnecting the Mississippi River to its delta is ultimately the only sustainable way to save Louisiana’s coast, the National Audubon Society’s Louisiana Coastal Initiative team has devised a way to put short-term local restoration efforts affordably in the hands of local property owners.

The John James dredge at Rainey.

For this, enter the John James, a 24-foot dredge operated by Karen Westphal, Audubon’s Atchafalaya Basin program manager, and Timmy Vincent, senior sanctuary manager for the Paul J. Rainey Wildlife Sanctuary, where the dredge operates.

Put simply, the pair hopes to demonstrate that small, independent dredges have the potential to create new land in areas where erosion and subsidence currently threaten wetlands and property lines.

Initiated and partially funded by TogetherGreen, a collaborative project between Audubon and Toyota, the John James’ work officially began on November 22, 2010, and for the past year Karen and Timmy have become part-time dredge operators in an effort to combat erosion in the sanctuary.

As with most new ideas, progress started slow.

“The learning curve has been rather bumpy,” said Karen, expanding upon the challenges of figuring out the finer points of moving sediment, but she quickly added that progress was improving. “It really works – we’re doing it.”

As evidence, throughout their dredging cells, the pair now sees alluvial flows – mini deltas of mud fanning out across the marsh. In times of lower water, birds, raccoons and alligators leave their tracks across the new mud, and on the primary test site, marsh vegetation – the backbone of the wetlands – has begun to take hold. Visitors can now walk down a boardwalk to the site and see bacopa, spikerush and three-square grasses fanning out along the new mud bed.

New land created by pumping sediment into a dredging cell at Rainey.

To move sediment and create this land, the dredge’s 15-horsepower submersible pump agitates the bottom of partially filled waterways. From there, sediment pumps through a 4-inch transport hose to the deposition area. The muddy discharge can be pumped into semi-contained open water (they often use reed barriers and plywood to build containment areas) to create new land or sprayed to distribute sediment more evenly through fragmented marsh.

At maximum efficiency, the dredge moves mud at a rate of 20 cubic yards per hour through the 4-inch hose over a distance of up to 800 feet, though as of yet, this ratio has been difficult to reach. Still, with the dredge’s low-fuel costs, two people operating the dredge at near maximum efficiency can create an acre of land one foot high in 75 hours.

More importantly, Karen and the Louisiana State University graduate students she works with to provide a full evaluation of the project estimate the total cost at less than $10,000 per acre of land. For coastal landowners facing rapid land loss, this certainly begins to look attractive, offering them an affordable way to snatch back land from the spreading open water.

“Even if you can create only an acre,” said Karen, “that’s an acre you haven’t lost.”

One Response to Audubon mini dredge: Building land at Rainey, one acre at a time

  1. Pingback: land-making machines – mammoth // building nothing out of something

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