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Impact of a course correction

October 8, 2012 17:54 IST

River Interrupted

Divya Karnad visits New Orleans, many parts of which are slowly sinking into the Gulf of Mexico, and examines how coastal cities deal with sea-level rise, hurricanes, storms and human influences on subterranean and support structures.

I wake up on a Friday in the French Quarter and there is already music in the air. It is not a big band, but a prelude to the rest, leading up to the Mardi Gras in New Orleans. The largest city in Louisiana, New Orleans also pays a high price for its wonderful French Creole culture. In the wake of Hurricane Katrina, the debate about the resilience of a vibrant coastal city like New Orleans has only heated up. How do such important coastal cities deal with the multiple pressures of sea-level rise, hurricanes, storms and human influences on subterranean land support structures?I am in New Orleans to learn how its wildlife and people are going to cope with their homes slowly sinking into the Gulf of Mexico. I drive past marshes and open water with pelicans circling their favourite fishing spots.

As the large brown and white birds settle, I see the remnants of old trees, scattered by Hurricane Katrina, now providing shelter to a solitary pair of bald eagles. The effects of the hurricane are still apparent in the fallen houses and dead trees. I wonder whether this disaster-in-waiting is just a product of circumstances or whether there are larger lessons to be learned.

The swamp beckons a concrete-weary explorer with a call that cannot be resisted. An hour on a shallow bottomed boat, watching alligators, egrets, blue herons, kingfishers and turtles, and suddenly the pace of life slows down. The swamp tour is just a half an hour away from the city but worlds away from the mayhem of Bourbon Street. The tour guide’s introduction to the history and ecology of the place leaves out some of the most significant changes that have sculpted the city-scape. Dams across the Mississippi have held silt back, and the river’s course was decided by virtue of the numerous cities that developed along its banks.

Any sudden changes in the course of the river would result in all those cities being washed away. This is what has allowed permanent urbanisation in the region and created the city of New Orleans. The creatures of the swamp have already dealt with the shift of the mighty Mississippi, but the city is just beginning to face its consequences. The river was tamed and imprisoned into a steady, predictable course in order to allow for the shrinkage of the marsh to make way for concrete. It is this, in combination with the lack of silt deposition, which is in fact, the largest threat to the region. Without the reinforcing silt from the Mississippi, the loose soils under heavy concrete structures are beginning to give way.

Combined with the effects of drilling for oil and boring for freshwater, land is sinking at a rapid rate. Consequently the city is now below sea level. Drilling has caused sea-water intrusions, blurring the lines between land and sea. Every storm surge is effectively higher and more potent as a result.

Similar problems, different rivers


River diversions and control are an ancient strategy. From the Egyptians to the Chinese several ancient cultures have dealt with problems of river flooding and subsequent loss of life or livelihood. However, recent studies from the Yellow River in China, the Sacramento in the US and from the Aral Sea of Kazakhstan and Uzbekistan suggest that large-scale human interventions repeatedly disturb the river’s natural cycles of erosion and deposition at its sea mouth. The Yellow River, for instance, fails to even reach its sea mouth during some months of the year. The Aral Sea is a stark example of the impacts that river diversion can have on a coastal area.

Originally, the Aral Sea was one of the largest lakes in the world, lying between modern-day Kazakhstan and Uzbekistan. In the early 1960s, the then Soviet regime decided to divert the two rivers, which fed this lake, for the purpose of irrigation. While this aided agriculture, it sounded the death-knell for fisheries. The entire lake nearly disappeared since massive evaporation rates were not complemented by river inflow.

The super saline waters that remain are not fit to bear life, and much of the area has turned into a salt-spoiled desert. The cities along its former shores lie abandoned and uninhabitable.

New Orleans reminds me of similar cities closer home. So many Indian cities occur at the interface between rivers and the sea. From Mumbai to Kolkata, the life giving waters are dammed, channelled and controlled. The interruption of river flow is only set to get worse with recent plans to further modify rivers. What are the consequences of diverting rivers, interlinking them, even? Cities like Chennai are already facing problems of salt-water intrusion. How much can the system take before it begins to break down?

River water after all brings life not only to the inland, but also to the coast. Without estuaries acting as nurseries for fish, we may never again be able to savour seafood. Entire coastal populations will lose their livelihoods. Massive changes to land and water cause seismic disturbances, such as those brought about by the diversion of the Mississippi River.

Beyond the obvious need for freshwater for irrigation, other, sometimes greater concerns begin to emerge. New Orleans is one of several indicators of things to come. To continue to ignore these issues is tantamount to deliberately causing a huge number of people to suffer in future. Present economic gain from rivers can never compensate for that.

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