Natural Infrastructure in the Gulf of Mexico
Nature plays a vital role in keeping the gulf resilient in the face of flooding from hurricanes.
The swallow-tailed kite is a handsome raptor of southern swamps with striking black and white coloring and a forked tail that it uses to bank gracefully above the forest canopy. If you were a swallow-tailed kite wheeling above the great Atchafalaya River floodplain in south Louisiana, you would see a million acres of cypress and tupelo, sweetgum and maple unbroken by roads and towns. And, today, the Atchafalaya basin would be filled with brown, silt-laden water overflowing from the flood-swollen Mississippi River.
The Mississippi River started to rise last November, reached flood stage in Louisiana just after Christmas, and remained at flood stage through most of the summer into August. This is the longest period of Mississippi flooding in recorded history.
In July, this protracted flooding interacted with a tropical system, as Hurricane Barry threatened to send a storm surge up the already swollen river and overtop levees in southeastern Louisiana. While the hurricane’s westerly track spared New Orleans from disaster this time, a changing climate means that more such flooding will be likely. This will put unprecedented pressure on traditional flood protection infrastructure.
While it may seem that nature itself is a threat, it’s actually an important part of the solution.
Natural Floodplains Absorb Excess Water
Natural floodplains are integral to the health of river systems. They give excess water a place to go besides the main channel, lowering flood heights and taking pressure off manmade flood barriers.
Just north of Baton Rouge, at the Old River Control Structure, the Army Corps of Engineers sends up to about 30% of the Mississippi’s water down the Atchafalaya River, a shortcut to the Gulf of Mexico. This takes pressure off the levees in Baton Rouge and New Orleans.
While the Atchafalaya has suffered its own hydrological manipulation, it can accept so much of the Mississippi’s water because it is not just a narrow channel confined by flood barriers. Its levees are set 15 miles apart, and in between the levees are a million-acres of wooded swamps and coastal marshes. The bottomland hardwood forests in the Atchafalaya are resilient to flooding. They absorb flood impacts by allowing water to spread out and up unimpeded by built-up areas.
Wetlands Provide Multiple Benefits
These wetlands have other benefits. They reduce nutrient pollution by processing excess nitrogen and phosphorus coming from agriculture and urban areas up the Mississippi. They are habitat for a diversity of plants, fish and wildlife. They store carbon, support a large crawfish industry and offer opportunities for hunting, fishing and watching wildlife.
Natural Infrastructure Funding Protects Communities
The Atchafalaya Basin is a prime example of what is termed natural infrastructure—natural features providing real and quantifiable services to people. And not just nice-to-have services, but those that save lives and communities from devastation in times of high water.
The Atchafalaya Basin is not unique. At other places around the Gulf of Mexico, planners and engineers are realizing that natural features and natural systems can be functional and cost-effective in reducing the risks of storms and floods.
In Houston, Hurricane Harvey’s torrential rains flooded parts of the city built on old bayous that had once carried water to Galveston Bay. Now, plans are being implemented to buy out homes and peel back development from some of those low areas to restore the bayous as corridors for flood waters and places for bicycle paths and outdoor recreation. This project will also save the government from paying for repetitive flood losses in flood-prone parts of Houston.
Natural features alone will not protect built-up areas from every natural hazard. New Orleans and Baton Rouge will still need their levees along the Mississippi River. However, as our country considers legislation to finance renewal of the nation’s infrastructure, restoring and protecting floodplains, tidal marshes and barrier islands should be as eligible for funding as concrete and steel storm defenses.
Those man-made defenses are costly to build and maintain. They are also vulnerable to the extremes of a changing climate. Meanwhile, natural solutions to flooding provide additional benefits: They process pollutants, store carbon, create opportunities for outdoor recreation, and provide a place for swallow-tailed kites to wheel above the trees in a landscape which, left alone, has been adapted and resilient to storms and floods for thousands of years.