Why Engineering with Nature Could Save New Orleans and the Mekong Delta | Jobs Vox


When we want to grow economically while protecting ourselves from nature, for decades the answer has been the same: Build big, expensive, gray infrastructure.

In many cases, such a big, expensive, gray answer has been a big mistake.

Gray infrastructure often becomes a set of unknowns – not just lifetime unknowns, but unknown and unintended consequences for the ecosystems surrounding the projects, ecosystems that millions of people often depend on for food and livelihoods.

We could have avoided these mistakes before climate change. In an era of extreme climate, we don’t have that margin. We still need protection from extreme climate impacts, such as record-setting droughts and floods in the same year. But now, we need to use nature to protect our investments as well.

So, when we build the infrastructure to defend ourselves, we need to consider nature as the infrastructure and engineer with nature to meet our goals.

The Unintended Consequences of Gray Infrastructure in NOLA and Vietnam

New Orleans (where I live and work) is protected by a perfect example of those unintended consequences from large, expensive, gray infrastructure.

Embankments and a flood protection system surround the city, where it sits like a small bathtub surrounded by gray infrastructure and the moat of water (Mississippi River) that surrounds it. When storms hit, the system is great for both keeping seawater out of the Gulf of Mexico and the rising Mississippi out of the city, which would be as devastating to the city as Hurricane Katrina in 2006.

But the combination of obstacles in the water creates another problem: all the water that falls In there’s only one way into town out – Gray infrastructure canals built around floodplain systems. New Orleans pumps groundwater into the ocean before a storm and uses that groundwater depletion as a buffer so that six inches of water doesn’t stand when six inches of rain falls on the city.

As a result, New Orleans is sinking. When water is extracted, groundwater pumping causes the soil to shrink and sink (a phenomenon known as soil subsidence). Meanwhile, no sediment is coming in from above to maintain the city’s height, as levees and flood walls keep the river from flooding the city and depositing sediment. As one study put it, “The more land subsides, the more groundwater has to be extracted to prevent groundwater flooding, resulting in further subsidence—a vicious cycle.”

Subsidence is also occurring in the Mekong River Delta in Vietnam, but for a different reason. Basically, Vietnam has built a dike around the world’s most productive rice-growing region to protect it from rising sea levels as well as flooding from the Mekong, a traditional method of irrigating fields .

The Mekong Ditch allows industrial rice growers to better control water levels and produce three rice crops a year. The problem: they are using groundwater instead of river water to irrigate the fields, and that groundwater withdrawals (in combination with the lack of full river sediment input by the flood-protection system) have continued to subsidence of the soil. is kept Meanwhile, salt water from the ocean is being drawn into the latter by the pressure differential created by freshwater extraction, increasing groundwater salinity and reducing rice yields.

Saltwater intrusion into the Mekong Delta is now exacerbated by another problem: less water is flowing into the Mekong Delta from upstream. Some point their fingers at China, which captures the river’s water in rapidly growing, large reservoirs. Others say it is a combination between climate-driven changes and a decline in basin-wide rainfall. Whatever the source, the issue is compounding. Vietnam needs a paradigm shift – and quickly – to address the resulting situation.

Solution: Engineer With Nature

Promising news: The government of Vietnam is making that change through Resolution 120, which creates a master plan for the sustainable development of the country’s largest agricultural region on the Mekong Delta. The nation’s authorities have proposed, among other things, to open the upper end of the dike to flood agricultural areas and control floods seasonally so that they flush salt out of the soil, and in essence, a device As align agriculture with the pulse of the flood. To maintain healthy soil and productive ecosystems.

There is science behind using flood irrigation to purge unwanted salts from the soil – in California, agriculture uses additional flood irrigation to purge salts left behind in the soil by evaporation from previous irrigations. But the restoration of the practice in the Mekong is the restoration of nature in a way to manage the human system.

Similarly, Louisiana’s Coastal Protection and Restoration Authority (CPRA) has developed a strategic plan for hundreds of nature-based restoration projects in the state—some of which are the largest in American history. The largest of these projects focused on breaching the Mississippi levee in strategic locations outside New Orleans, and using sluice gates at breaches to keep fresh water and sediment in and out when major floods occur.

The projects combine a resilient built natural infrastructure system. In essence, the goal is to flood coastal forests to keep them as healthy as they would be in a natural floodplain. These forests, in turn, protect people from the fury of powerful storms. The overall scheme is a beautiful combination of built and natural infrastructure, using the built to moderate and enhance the restoration results of the natural.

Resolution 120 in Vietnam would allow regional governments to make similar breaches in the Mekong embankments to manage agricultural land. From my point of view, farm is also natural infrastructure and we don’t think twice about managing it. Aquifers and flood plains should be managed in the same way.

Importance of a Scientific Framework

As a scientist, I naturally wonder how we determine what engineering will work best with nature’s approach, especially if they are replicated across space and time. Imagine that CPRA of Louisiana does 100 projects over the next 50 years. Not all of those projects should be done in the same way. Instead, engineering with nature dictates taking great care initially about measuring results, experimentally determining the projects that produce better results, and applying those insights to the next project and the next. generate an endless cycle of adaptive learning and management.

CPRA has already done excellent science and world-class modeling to plan its interventions (some of which was done at Tulane, my home institution). In the case of Vietnam, the resolution calls for more research-science to drive sustainable development of a more integrated built natural infrastructure system. The rapid deployment of projects such as these in Vietnam and Louisiana is essential to ameliorate the unintended consequences of the net-built infrastructure approach.

But we also need to be careful to apply engineering with nature within an evidence-based, scientific framework—what I call “diagnostic testing for planetary health”—so that we can learn from our mistakes. As with the gray infrastructure projects of the last century, engineering restoration with nature will produce unintended consequences – and understanding them within a scientific framework is critical to ameliorating them.


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