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A multi-billion dollar system of levees, levees, pumps, and other flood control measures helped protect New Orleans from the tide of ocean water that was carried away by Hurricane Ida. But Ida also encountered natural barriers such as wetlands, which act as a “speed bump” and mitigate the effects of storms.
Although natural defenses have their limits – especially during major events like Ida – experts can say that they can play an important role in protecting communities and the environment during storms.
“Having these wetlands between you and the storm always has an advantage,” said Gerald Galloway, a recently retired engineering professor at the University of Maryland who previously worked for the US Army Corps of Engineers.
Since the devastation of Hurricanes Katrina and Rita in 2005, an important part of Louisiana’s efforts to strengthen its storm defenses has been restoring the wetlands and barrier islands that the state lost for decades along its coastline.
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HOW DOES NATURAL TERRAIN PROTECT AGAINST storms?
Wetlands and other natural terrain can act as buffers for wind and water, making storm surges more difficult to overcome before they can reach people and buildings.
“They help with storm protection because they use energy,” said Hugh J. Roberts, chief operating officer at the Water Institute of the Gulf, an environmental research group.
Roberts compared it to a cyclist riding over rocky rubble. Barren wetlands are like a ride over a few pebbles, he said – barely noticeable. But rugged wetlands with elevated terrain are like trying to drive over a long, bumpy dirt road.
The Water Institute was funded by the Walton Family Foundation, which also supports The Associated Press’s coverage of water and environmental policy.
What about big storms like IDA?
Wetlands are generally more effective at reducing the effects of small to moderate ocean waves, said Ed Link, a researcher at the University of Maryland who previously led an analysis of New Orleans to Katrina storm protection.
With larger storms like Ida, the effect can be more subdued. Once wetlands are filled with water, they lose their ability to brake waves and the storm can sweep over them, Link said.
Philip B. Bedient, who runs a Severe Storms and Flood Center at Rice University, agreed that wetlands are ideal for smaller events that can bring winds of 100 mph (161 km / h) but are beaten by larger storms can. Ida was a Category 4 storm and had winds that reached 150 mph but did not drive as much storm surge ashore as Katrina.
However, experts say that even in large storms, natural barriers can provide another line of defense and can make a difference. At Ida, officials say it will take time to assess its impact.
According to a study by researchers from the University of California Santa Cruz, the Nature Conservancy, and the Wildlife Conservation Society in the northeast, areas with coastal wetlands suffered an average of 10% less property damage during Hurricane Sandy compared to those without.
HOW IS THE STATE BUILDING NATURAL DEFENSE?
Louisiana has invested heavily in restoring its natural barriers to protect itself from storms.
As of 2007, the state has created or restored approximately 76 square miles (197 square kilometers) of marshland and 60 miles (97 kilometers) of barrier islands.
And the state’s latest coastal protection and restoration plan includes dozens of projects building or maintaining more than 2,072 square kilometers of land. The total cost is estimated at 50 billion US dollars – but the projects are expected to prevent damage of more than 150 billion US dollars over the five decades. They include plans to use dredging material and diverted sediment to help build swamps.
“We’re trying to hold the line or do our best to make sure the wetlands keep the Gulf away from the cities,” Galloway said.
IS THE RESTORATION WORKING?
Despite ongoing work, the state’s restoration work is not keeping pace with land losses.
Louisiana has been losing land since at least the 1930s when flood control measures along the Mississippi stopped the natural process that deposited sediment from the river into the delta. In 2012, state officials predicted their restoration work would eventually reverse the problem. Five years later, they stopped making that prediction.
The Louisiana Coastal Protection and Restoration Authority now says the restoration will only slow the loss.
ARE THERE OTHER BENEFITS OF WET LANDS?
In addition to flood protection, wetlands can also help contain erosion and preserve the landscape. They also provide habitat for fish and migratory birds.
The magnitude of the environmental benefits can be significant. Louisiana provides winter habitat for 5 million migratory waterfowl, and its fishing industry provides a quarter of the country’s seafood, according to a state report. Louisiana’s wetlands also make up half of the country’s coastal marshland, the report said.
How this wildlife habitat survived the storm is not yet clear. A spokesman for the Louisiana Coastal Protection and Restoration Agency Chuck Perrodin said it could be weeks before the agency can assess the extent of the damage to the state’s coastal projects.
But between 2004 and 2008, Louisiana lost more than 300 square miles (777 square kilometers) of land to hurricanes.
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The Associated Press is supported by the Walton Family Foundation for reporting on water and the environment. The AP is solely responsible for all content. You can find all of AP’s environmental reports at https://apnews.com/hub/environment
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