13-16 feet above sea level? It's very close to the ocean, in the middle of a swamp. Do they have a levee or something?
Ok, I'm not getting very far with this. Trying to check elevation data across multiple software programs doesn't give me anything because all the map programs use essentially the same dataset, the SRTM data from shuttle mission STS-99.
We have the report that the water topped the Jefferson Parish levees near Gretna, but the tops of those range from 5 to 9 feet and that doesn't tell us much.
We have some confirmation from gpapa's link showing river water at 13.1 feet above normal at Lafayette, but that still doesn't give us normal.
A transit and a known good benchmark would do the trick, but that's a little far away and it's kind of wet there, so for now, I'm going to retract the 20 foot surge claim south of NO and chalk the anomalies up to funneling effects until I hear otherwise.
That leaves us with dam wrecking winds inland and buildings down there too, while buildings on the coast are mostly just missing shingles.
Maybe they were old masonry buildings and the dam was poorly built.
There is always a risk in trying to construct a big picture from isolated anecdotal reports. If this is a case of that, I apologize for getting anyone upset.
On the bright side, the truth will come out over time, it always does. I'll try to be more patient until then.