Reyn wrote:I have a New Orleans question for some knowledgeable person here:
Parts of this city are below sea level, is this correct?
I understand the various levies failed to hold back the water. Do you think it would have made a difference if this area had had a proper dyking system like in The Netherlands?
I remember vaguely the big flood in 1954 there. I was born in Holland, but I was 3 at the time. Since that big flood, the Dutch have made huge improvements in flood control. Very expensive, of course, but it was all worth it.
Parts of the city are as much as ten feet below sea level. Those portions which are above sea level, however, are subject to flooding because of the levees which are meant to prevent flooding in times of high water in the river, the canals which lead through the city from Lake Pontchartrain to the river, and the levees at the lake. When d'Iberville (who came from Canada, by the way) established his settlement on Lake Pontchartrain in 1699, the water level was about the same as today, which meant that the site was acceptable, as heavy rains from storms did not make that big an impression on the lake, and water could drain off into nearby bayous. When his brother de Bienville establihed New Orleans (1718), it was well above the level of the river.
However, as the modern city has spread out, the lake has been dyked with levees, as has the river, to prevent flooding of any kind. The original settlements could afford to ignore flooding in nearby low lying areas, but that is not true of a city of a half million people spread out over an area more than twenty times the size of d'Iberville's and de Bienville's settelments combined. The Mississippi is not in its "preferred" bed, it was diverted several hundred years ago from a wide, deeper bed which is now the Atchafalaya River and Bayou, by a massive deadfall of trees, perhaps caused by an earlier hurricane. Over time, it likely would have returned to its old bed, but with the city established and growing, the Corps of Engineers had worked to keep the river in its current bed. Northwest of Baton Rouge is the Old River Control Structure which prevents the river from returning into the Atchafalaya bed. So the river at the best of times is not much below flood stage. The additional problem of extensive levees along the course of the river to the north, and the rivers which feed it mean that a far greater volume of water is subject to flow in that bed than was the case in the early 18th century. It actually doesn't take much for the river to rise to a point at which it would have flooded the ground as it lay in the days of d'Iberville--hence, the extensive levees.
Finally, two things are notable. The first is that the evidence from the collapse of the levee at the 17th Street canal is that the levees were built in a very shoddy, substandard manner, with inappropriate fill. This is evidence of the venality of greed, and of improper or no official supervision of the construction. The other notable thing is, the preservation of the river in its current bed has more to do with the oil refineries and their chemical plant consorts on the river corridor between New Orleans and Baton Rouge than it does any concern with the fortunes of either city. Were the cities not there, it is still likely that the Old River Control Structure would have been built (1963) to preserve that corridor. One can't automatically assume that all of the expense and engineering was in aid of human convenience, apart from the employees and share holders of the corporations which run the refineries and chemical plants.
