Lessons gleaned from Hurricane Katrina might alter restoration plans
Highways, levees, and navigation channels must be planned in harmony with coastal restoration projects.
For years, scientists working along the U.S. Gulf Coast have complained that infrastructure projects, such as highways and levees, are undermining coastal restoration projects. When Hurricane Katrina ripped through Louisiana’s coast on August 29, the complaints were dramatically demonstrated. The storm surge that devastated New Orleans was funneled into the city by the levees and navigation channels that researchers say have gradually destroyed coastal barrier islands and wetlands over the past century. The government has largely ignored the scientists’ calls, but can a route to recovery now be found?
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The 15-year push to restore Louisiana’s coast culminated in 2004 with the publication of the Louisiana Coastal Area (LCA) Comprehensive Coastwide Ecosystem Restoration Study, a scheme that is potentially even larger than the $8 billion plan to restore Florida’s Everglades. Worked on by more than 120 university scientists, staff from the state of Louisiana, the U.S. Army Corps of Engineers (Corps), and other federal agencies, the projects recommended in the LCA aim to reverse the deterioration of Louisiana’s remaining 4600 square miles (mi2) of coastal marshes and swamps. Since 1930, Louisiana has lost more than 1500 mi2 of marshland to erosion and subsidence, and the state is still losing 25–30 mi2 every year.
“Right now, we’ve had a lot of discussion about whether we need to re-examine the projects we proposed under the LCA,” says Gerry Duszynski, acting assistant secretary in the Louisiana Department of Natural Resources’ (DNR) Office of Coastal Restoration and Management. The LCA still provides a strong framework for the restoration, but some of the projects have a much higher priority than they did before the hurricane. For example, a top priority is to restore the barrier islands, because they create an instant speed bump for storm surges, he says.
Another first-order project is creating a land bridge on the eastern side of Lake Pontchartrain, a brackish estuary, to close off outlets to the Gulf of Mexico that allowed the storm surge in. Planners have also discussed ways to improve coordination between the managers of flood control systems and restoration projects, Duszynski says. For instance, the old levee systems drained and destroyed wetlands, leading to subsidence and increased risk of flooding. Instead, state and Corps planners are considering a leaky levee system with water control structures that can maintain water flow to wetlands inside the levees most of the year but cut off the flow of water during storms.
The levees that protect homes and businesses from flooding are partly to blame for the state’s land loss, because they prevent Mississippi River sediment from replenishing the marshes, according to the Louisiana DNR.
Without a continual supply of new sediment, the marshes gradually submerge from natural subsidence of the Mississippi River Delta. Canals and channels dug to ease navigation and exploit oil and gas reserves under the delta have also contributed to marsh collapse by speeding erosion. The loss exacerbates storm impacts, since storm surges drop by 1 foot for every 2.7 miles of marshland they cross, says Duszynski.
“The state has been asking for federal restoration funding for over 10 years,” Duszynski says. The levee systems were built to depend on the substantial wetlands’ buffering capability of years gone by. Now that the wetlands are gone, the old levees are still in place, leading to more flooding and more pressure on the levees. “But no one from out of state bought into this,” he says.
Congress has only provided the state and the Corps with $50 million annually since 1990, which is far short of the $14 billion needed to restore the coast. Only a handful of restoration projects had been initiated before Katrina. But even with the LCA, most of the projects would simply hold the line on marsh loss. If nothing is done, an additional net loss of 328,000 acres may occur by 2050, which is almost 10% of Louisiana’s remaining coastal wetlands, according to the LCA.
Integrating public works and coastal restoration projects is one of the most important ways to change the planning process, says Barry Kohl, a geologist at Tulane University. “The Corps is responsible for restoring wetlands, while on the other hand, it still has civil works projects on the books which would disrupt the coastal restoration,” he says. A prime example is the Mississippi River Gulf Outlet, a 1950s-era navigation channel that has now been shown to have amplified and accelerated Katrina’s storm surge, he says.
Although the Corps acknowledged this problem in the LCA proposals, some Corps staff members want to perpetuate the civil works projects, some of which date from the 1950s, even though they no longer fulfill the needs they were meant to address years ago, he says. Congress directs and funds all of the Corps projects, says Alan Dooley, a Corps spokesman.
“The governor’s office of coastal activities has been adamant in arguing that highways, levees, and navigation channels need to be planned in harmony with coastal restoration,” says Len Bahr, coastal science adviser to Louisiana Governor Kathleen Blanco (D). New infrastructure, such as updating the east–west highway I-49, must be evaluated for its impact on water flow. The governor is also advocating that the LCA be managed by a federal–state partnership.
“The main thing is that the storm has forced people to talk about coastal issues who never did before, such as business people—now everybody is starting to see that we’re all in this together,” Bahr says.
