Next empire up built Baghdad on the Tigris.
The rationale was that modern forms of transportation (camels) made it economically feasible to transport goods to and from the Euphrates to points along the Tigris, so why continue to take the risk of having a big city on a dangerous river.
Once upon a time the Hwang-Ho (Yellow River) in China relocated itself several hundred miles. Millions of people died in the transit. This had no effect whatsoever on trade since ancient emperors had already built canals between the Hwang-Ho and Yangtze basins, and they continued to serve all needs.
One day New Orleans slipped below sea-level thereby necessitating a relocation of the residential and retail areas to upland areas. Special protective levees were constructed around important port and industrial facilities. Although they lost power in the area, it was only a few days until the most important commercial activities in the area were back in business.
In the future, the people who reside in the New Orleans area for the purpose of manning the port facilities and tourist hotels will live further West where the land is above sea-level.
The Ten-Tom is a long way around but I am trying to look at the long term. I want this country to prosper long after I am gone.
Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)