Fortunately, the levee held. That was not the case a few miles downstream in 1871. This illustration for Harper's Weekly demonstrates the power the river unleashed at the Bonnet Carre Crevasse.

“A crevasse is a natural break in a river levee and sediment comes out with the water,” Dr. Denise Reed, a professor of earth and environmental sciences at UNO.  She says one or more of these breaks is likely responsible for an interesting phenomenon in a lot of neighborhoods including several in LaPlace.

Most of the ponds were dug nearly ten years ago and when they were developers were surprise to find cypress stumps that had grown nearly 10 feet below the current ground level. No one had any idea they were there until digging equipment started running into the obstacles.

“What you're seeing is subsidence. The land sinking down, thousands of years ago probably those cypress trees were at the surface,” Reed said.

That's right, she said thousands. Reed believes based on the depth of the trees scientific dating could find those trees to be at least 2000 years old.

“Those cypress trees might have been growing for quite a long time after they started to get covered with sediment,” according to Reed. She thinks a major break in the natural levee could have put an end to these particular swamps.

“You can get massive amounts of sediment coming out in a short period of time. That might be the kind of thing that would really lay down the thick package of sediment quickly,” she said.

LaPlace is in just the sort of place you might expect to find an ancient break.

“It often happens near bends in the river which is where LaPlace is in a bend in the river,” she said.

Interestingly the sediment from these floods is probably what made the area a great place to build a town.

“There are these cycles in how coastal Louisiana has developed it's not one thing happening all the time, but kind of a sequence of events and that's exactly what we're seeing when we see those cypress stumps way down below the ground level,” Reed said.

Almost all of the land where the city is today used to be the sugar cane fields of the Gaucheaux Sugar Plantation. The developers that built these subdivisions still have the old maps. USGS surveys show that at seven to 14 feet above sea level it is still some of the highest land in the parish that far away from the river.

Reed came up with the 2000 year date based on land sinking atapproximately one half centimeter a year. For a more precise age to thetrees samples of the wood could be sent to a lab for carbon-14 dating.

“It's a good thing because that means that you have some really good sediment in place,” Reed said.   And neighbors have a really good story to tell about the ponds in their backyards.