Flood number 5 drowned the center of the city. Surge that found its way into Lake Pontchartrain gained access to the city through breaches in two drainage canal levees. Then   for three painful days water from the still swollen lake poured through the breaches into Lakeview and Gentilly, rolling across Mid City, Broadmoor, Old Metairie and into Carrollton, reaching up Canal Street surrounding the Superdome and wetting the fringes of the CBD and the French Quarter.

It started because the levees along the drainage outfall canals failed when their concrete superstructures were deflected backwards by water pressure and wave action. The deflection opened cracks into the heart of the levee allowing the pressure to push the entire levee backward off its footing. Breaches in the 17th street canal and the London Avenue Canal resulted from these types of failures. The big breach at the 17th Street Canal is shown above. You can see where a 200 foot long section of levee has just been shoved aside.

Preventing outfall canal breaches will be fixed. Moving the pumping stations to the lake front and protecting them with breakwaters is the ultimate solution. This takes the pressure off miles of canal levees because the stations themselves act as floodgates and prevent the buildup of surge in the canals. This is exactly how all the pumping stations in Jefferson Parish are configured. The administration requested Congressional approval for funds ($200 million) to build new pumping stations at the mouths of the outfall canals but Congress declined, claiming the need for further study.

So for now the pumping stations must stay where they are, and the Corps is spending tens of millions of dollars building temporary flood gates of removable sheet piling until an ultimate solution is designed. However this temporary solution introduces another problem, namely what to do with the rainfall accumulation in the city when the floodgates are closed. Flood gates in the outfalls canals at the lake can be left open normally then closed if a storm threatens. But when the gates are closed the old pumping stations, far inland must be shutdown because there is nowhere for the water to go. Rainwater accumulations can flood the low lying parts of the city too.

So the Corps has added temporary pumps to the temporary flood gates. But the temporary pumps can't move as much water as the pumping stations and the potential for rainwater flooding is still present in the event of a storm of sufficient magnitude to require closing the flood gates. However the advantage of this design over the levees is that the flooding would be limited, slow rising and could be pumped out quickly after the storm passed. (As almost an aside, the Corps is having significant difficulty in late 2006 getting the temporary pumps working at all. Vibration problems with the pump motors limited pumping capacity to just a fraction of the design and the city remains at elevated risk until these problems are solved.)

The Corps has also committed to restoring the Pumping Stations damaged by flooding. The electrical motors in these stations must be rebuilt. Immersion in brackish water for a 42 days is not recommended for copper windings and high load bearings. Like many other Corps projects this is taking a curiously long time to accomplish. By November 2006 only three of the eleven stations had been completed. Others were battling fires and mechanical failures as they tried to stay in service.

Interior levees can provide additional compartmentalization so that no failure can have such widespread effect again. Designated ponding areas and internal pumping capacity can help avoid rainwater induced flooding. An innovative design for sunken pump barges (see BNOB Levees) may be able to keep the water flowing out of the city even when flood walls across the outfall canals are closed.

With all this said and eventually done, homeowners should never again be comfortable to build slab homes in such low lying areas as Lakeview and Broadmoor.  Historically and in the future New Orleans must build its homes on raised foundations and as near the natural levees as possible.

From a vantage point to the SSW of the dome we look NNE across the CBD, Mid CIty, Gentilly and toward the lake. The French Quarter and the River are outside the picture to the right. Flooding around the Dome reached a maximum of three feet and what you see here is more likey two feet or less.