The report by scientists at Southeastern Louisiana University is aimed at providing background information for a proposed $56, federal-state project that would divert about 2,000 cubic feet per second of river water into the swamp through the Hope Canal near Garyville.
Protecting the Maurepas Swamp is important for the variety of wildlife and fisheries within it, and because it provides protection for nearby populated areas from storm surge from Lakes Maurepas and Pontchartrain during hurricanes. The wetlands also are part of a land bridge that separates the two lakes.
“Before we conducted this study, no one really knew how degraded the Maurepas Swamp was,” said SLU biology professor Gary Shaffer, the report’s lead author. “Even though the swamp is degrading, the trees are still alive, and from an airplane it still looks like a swamp.”
Tree quickly dying
But the three-year study indicates the swamp’s soil is sinking faster than growing roots and falling leaves and branches can fill it in, he said.
Repeated invasions by saltier water pushed west through Lake Pontchartrain into Lake Maurepas are killing trees at an alarming rate, he said.
And the lack of nutrients and sediment in the Mississippi River water has slowed the growth of trees and other vegetation.
One of the biggest discoveries of the study is that stagnant water often stays in interior areas of the swamp for much of the year, the result of a lack of flushing by freshwater and because the swamp interior has sunk lower than Lake Maurepas, and it cannot drain.
“We didn’t know how nearly permanent the flooding was,” Shaffer said.
Begun in 1999, the SLU study was affected by two weather extremes. In 1999 and 2000, southeastern Louisiana experienced a record-breaking drought that exacerbated subsidence and increased saltwater intrusion. In 2002, the back-to-back hits by Tropical Storm Isidore and Hurricane Lili also forced salt water deep into the swamps for months.
“The most shocking effect of the drought was the high salinities that we saw coming in,” Shaffer said.
Killer salinity
The entire Maurepas-Pontchartrain system became saltier from the lack of rainfall that normally feeds streams that lead into the two lakes. Quantities of salt “easily high enough to kill tupelo gums” were common, he said.
And despite heavy rains in November 2000, the swamp soils seemed to retain the salt, he said, which explains why tree deaths continued to increase throughout the swamp for two years after the drought.
“In some sites in close proximity to Lake Maurepas, up to 25 percent of the trees that we tagged in 1999 are dead now,” he said.
As part of the study, SLU researchers also fertilized some squares of land within the swamp to mimic the effects of river water, which contains high levels of nitrogen. They also measured growth in areas near canals and bayous where more freshwater flows naturally.
The results indicate the reintroduction of river water will increase the growth of trees and other swamp plants. Tree roots, especially, will grow more quickly.
Construction two year off
The diversion project is a long way from construction, said Ken Teague, who is shepherding the project for the federal Environmental Protection Agency.
The Breaux Act task force, which oversees smaller wetlands restoration projects in Louisiana, has authorized spending $5.2 million for engineering and design of the project, Teague said. Construction money will be requested when that work is completed in about two years. In addition to Shaffer’s research, the EPA has contracted with URS Corp. to model the potential for flooding of nearby communities from the diversion, including Garyville.
“It will take a year or so to model the runoff and resulting water levels south of Airline Highway,” Teague said.
Shaffer said officials also have met with local government officials to discuss the possibility of nearby communities building pumps to dump runoff into the diversion area.
An outline for logging
And scientists, environmental activists, state officials and representatives of the state’s forestry industry also have been meeting to solve another concern: resurgence in cypress logging in the Maurepas Swamp.
At a meeting Thursday, officials agreed to work on a map that would outline areas where sustainable logging could be practiced, and areas where trees won’t regrow it they’re logged, said Carlton Dufrechou, executive director of the Lake Pontchartrain Basin Foundation.
Sustainable logging is the proactive of cutting trees in areas where they can regrow, or cutting a limited number of trees and then replanting the logged areas.
Dufrechou said state officials also are researching way of using oil spill recovery money to protect the most sensitive areas of the swamp near Lake Maurepas, either by purchase or through conservation easements that would prohibit logging. The state receives money from companies and individuals involves in oil spills that is designed to compensate the public for environmental damage.
For more information about the Maurepas Swamp project, visit the Web site: Environmental Protection Agency - Maurepas Swamp