@UncleGizmo
The problem with putting anything on the
batture (that section of the riverbank between the levee and the river itself) is that when the river is at flood stage in springtime, you need something to handle high water that might be 19 feet over the normal winter levels. That is because that 19 feet is official "flood stage." The river at non-flood stage moves something like 593K cu.ft./sec. (=4.44 million gallons/sec) and at the foot of Canal St. in New Orleans (that's the "main drag") the flow rate is about 3 mph. That is 18,500 TONS (U.S.A. standard) per second of water. At that point, the river bottom is 200 feet deep. The stress factors are tremendous and nobody wants to risk any major developments on the
batture. Part of the problem is that south of the lake, we have no bedrock for at least 1500 feet so you need some humongous pilings. With our water table, building something massive can be a disaster.
There is a story about the Louisiana Superdome. When it was being built, an out-of-town contractor won low bid on the pile-driving contract. But they had done no tests of the soil So the day of the first piling arrives, they set up their equipment, drop the hammer on the first piling. On ONE stroke the piling slides all the way into the ground. They move the crane to pick up the next piling and the first one starts to float back up out of the ground. The supervisor calls his boss, the boss calls the Superdome Commission offices, and they pick up their equipment and people. They forfeit the penalty clause and revoke the contract. They knew they would go bankrupt to finish the contract because it would have taken two or three times the equipment and maybe 5 to 10 times as many pilings as they had estimated.
When you drive pilings in our area, you need to have at least two pile drivers. One drives while the other sets up the next piling to put on top of the previous one. As soon as the first driver is done he rotates the rig away while the other driver rotates in with a ready piling. It is almost like a ballet to watch the coordinated efforts of two giant pile drivers down here. The goal here is not to hit bedrock (because you almost can't), but to put enough pilings down to "float" the heavy stuff based on the bouyancy of a vertical stack of pilings. And of course, the "soupiest" soil is closest to the river or the lake where the water tables are highest so that is where you need the most pilings.
For that reason, building a luxury apartment complex on the river side of the levee is highly unlikely, though some apartments do front the River Road on the outside of the levees. When I was a kid, my neighborhood abutted the levees. I used to walk about a half of a block to get to the levee and hike for exercise. (And to take wildlife pictures - lots of water fowl in the area.) At night I could hear the propellers on the ocean-going tankers and freighters. I could tell by the sound whether they were loaded or empty because the ones riding higher in the water made a "slapping" sound or "splashing" sound whereas the ones riding lower just hummed and rumbled.
You told me they were the levees to keep the water back, the ones that didn't work in the hurricane debacle.
Just for clarification, I would have said those levees were LIKE the ones that failed. No river levee failed with a major breach that I recall but a half-dozen drainage canal levees DID fail badly at a time when rainfall was extreme. One of the company's night computer operators had an apartment across the 17th Street canal that breached and flooded what we call the Lakeview subdivision. He said it shook his apartment like an earthquake and the noise was horrendous. (He lost no property though due to flooding he had trouble getting in and out of there for a while.) The link is to a Wikipedia article and it includes an aerial shot of that location.
en.wikipedia.org
Most of the time we pump water into the lake because it has an outlet to the eastern end, called the Rigolets Pass. No problem to put large amounts of water in the lake other than it screws up certain types of fishing. From Lake Ponchartrain any water empties into Lake Borgne, which some folks think should be called Bay Borgne. Me? Don't care, I'm not that picky and the maps call it a lake at the moment. From Lake Borgne, the excess water directly empties into the Gulf of Mexico. The drainage from Lake Ponchartrain to the Gulf of Mexico is thus unimpeded by land. But storm surge can (and in the case of Katrina, DID) reverse the normal flow patterns through wind pressure.
What happened in Katrina was a multi-whammy. Some drainage canals were under extreme stress and failed. In other cases, such as nearer my home, the drainage canals weren't working right because the pumps had failed. Nobody was there to restart them, because the employees were released to head to the north shore of Lake Ponchartrain, which is slightly higher. The drainage canals, being INSIDE the levee system, don't themselves have levees. So the water just rose up from the canals and flooded the streets. To a level that at our house translated to about two feet of water inside the house. Took them three WEEKS to get the pumps running and because of the levees, you can't drain the canals UNLESS the pumps are running to lift the water over the levees.
