National Geographic article about New Orleans

I may be a fool here, but Karina did not flood New Orleans. The mistakes made by the corps of engineers and shoddy upkeep of the levees that broke flooded the city. This falls on the Federal Government. Of course the coastal erosion (Corps of engineers and oil companies) is also to blame on the long term issue of depleting coastline.

As far as moving the shipping 150 miles upstream, isn't there something to do with the riverbed and lack of clearance even with dredging that would make that impossible?