TED Talk | Kotchakorn Voraakhom

The latest projections of global warming, in multiple scientific studies and more specifically in the reports released by the International Panel for Climate Change (IPCC), show different effects in coastal areas for scenarios between 1.5 and 3 grades centigrade. Most of the “terra firme” lowlands predicted to become submerged are deltas built by rivers over the last few thousand years. Due to the fertility of these river-made territories, deltas are some of the most productive lands, responsible for feeding hundreds of millions of inhabitants of the planet. While new technologies may mitigate some of these food-production shortfalls, there are no techniques yet available or being seriously developed to save cities located in the deltas, such as the case of the Mississippi Delta.

The loss of the Ganges river mouth will reach the capital of Bangladesh, home to nearly 40 million inhabitants in its metropolitan core. Half of the Netherlands, and many of its most critical cities (with world-class infrastructures, such as the port of Rotterdam or Schiphol Airport) are under threat. Likewise, situated on the continental-scale delta of the Mississippi River, perhaps the most idiosyncratic city of the United States—New Orleans—faces an uncertain future.

The Mississippi Delta is one of the world’s largest, best examples of a river-dominated delta, with the river and its distributaries building land along the Gulf of Mexico for over 4,500 years. Contrary to other riparian morphologies in which the river collects runoff, in this alluvial delta the river forms the highest ground and distributing sediments through a system of distributaries. The main trunk of water builds a natural levee that, under natural conditions, occasionally overtops its banks or breaks seasonally flooding, nurturing and physically building new land with the sediments in its water column.

New Orleans is inextricably linked to its unusual geographic condition

Situated on the lowermost Mississippi River, New Orleans was accessed initially from the Gulf of Mexico through the brackish Lake Pontchartrain and several bayous. Although it became a premier commercial hub of the Americas in the mid-19th century, today it is far from being a major US city.

New Orleans and the Mississippi Delta are now facing extraordinary challenges. The flood mitigation systems—that is, artificial levees along the river—have stopped the distribution of sediments, which instead are lost to the ocean through the main mouth, thus accelerating land loss. The coastal erosion is aggravated by the loss of marshland, critically affected by the drainage of the territory and the oil extraction canals that introduce saline water into the ecosystem. Worse yet, sea level rise nearly doubles the relative rate of absolute subsidence, and exponentially increases the fragility of the fraying delta.