With hurricane season upon us, local thoughts are returning to the condition of New Orleans’ levees. This is especially true for residents whose yards back up to them.
After all, mere months prior to Hurricane Katrina, residents near the 17th Street Canal breach had reported water pooling in their yards and were told by the New Orleans Sewerage & Water Board that the water was coming from the canal.
But the Army Corps of Engineers — the agency responsible for the performance of the canal’s floodwalls — was never alerted. And of course, the 17th Street Canal failed catastrophically a short time later.
It is reasonable to assume that better maintenance inspections and better reporting of problems by the Orleans Levee District would have resulted in the seepage being brought to the attention of the Corps, which possibly could have prevented the breach.
Was the seepage a harbinger of bad things to come? The answer is no.
Today, it is not contested that design flaws caused the breach of 17th Street Canal. According to the corps’ levee study, the breach began at the north end of the 450-foot wide hole. The remaining sections were washed away, one by one, by the water flowing through the breach.
But the residents who were reported the seepage lived about 800 feet away, a long distance in terms of geotechnical engineering.
The pooling water was most likely due to a very localized condition such as water seeping through the interlocks of the sheet piles and flowing through a pocket of organic material or an abandoned sewage pipe. Or both.
Even had the pilings been driven to proper depths, this seepage could still have occurred. Seepage is fairly common along levees — including the Mississippi River levees.
The suggestion that the OLD should have seen evidence of the Corps’ flawed designs may be rooted in verbal interviews conducted in November of 2005 with the first levee investigators to arrive at ground zero. But that was too soon and an environment too chaotic for the experts to attain all the data needed to solve such a complex puzzle.
Information continued to surface until as late as November 2014.
After Katrina, the Corps rewrote the guidelines for levee maintenance for all levee districts in the nation. The 55 percent of Americans living in areas protected by levees are now safer.
But the seepage of the 17th Street Canal was very likely a red herring, not the canary in the coal mine. People protected by levees are better served by focusing on the true causes of the flood rather than the imagined ones.
H.J. Bosworth Jr., P.E.
lead researcher, Levees.org