A big negative that could be a positive

On either side of the Bonnet Carre Spillway, in both Kenner and LaPlace, are massive digital signs that read “NO STOPPING ON BRIDGE NEXT 12 MILES.”

The reason for the warning is that what is going on under the Interstate-10 overpass is a sight to see.

Water the color of the best drink Cafe du Monde has to offer is rushing from the river to the lake. Actually, “rushing” is too gentle a word.

At the river’s crest, 316,000 cubic feet of water every second exited the spillway and entered Lake Pontchartrain. Not only was the water pushed by 5 knots of current, it was also falling from as high as 17 feet above sea level all the way down to sea level in the lake.

The result has been water that races across the six-mile spillway like it’s late for a hurricane party. Trees in the spillway that stand defiant against the force see 2 feet of variance between the water height on one side of the trunk and the gaping eddy on the other.

In pancake-flat South Louisiana, it’s a spectacle that sightseeing motorists have found irresistible, causing slow-downs, traffic jams and sore necks on the spillway bridge.

As impressive as it looks, the very speed of that water is like a clarion call of government waste and stupidity.

Because the Bonnet Carre is channelized — it’s a fairly consistent two miles wide along its six-mile course — water careens through it without losing much momentum at all. That means that the sediment the river carries — the mother’s milk for the marshes — stays suspended until the water loses its energy somewhere out in Lake Pontchartrain.

What also stays suspended in the water are the nutrients that have washed off of farmers’ fields in the Midwest. That nitrogen helps all plants grow — not only the corn for which it was intended in Iowa — so when the algae in the lake run across it, it’s like Rosie O’Donnell at an all-you-can-eat Chinese buffet. The supply of nitrogen is virtually endless, and the algae never get full.

Super-charged under the sun of a South Louisiana summer sky, the algae go crazy, forming blooms that are so massive they literally block out the sun. As a result, photosynthesis stops in the algae underneath the surface, and they die. As the algae decay, they rob the water of oxygen, causing massive swaths of hypoxic water that is entirely uninhabitable for fish and shellfish.

I saw Capt. Dudley Vandenborre at the Back to the Beach Festival in June, and he said that his son, a commercial crabber, regularly found dead crabs in his traps after the 2008 opening. The crabs would climb into the traps in good water, but the bad water would move through the area, killing everything that couldn’t swim away.

Vandenborre is concerned that, with the Industrial Canal being closed, it’ll take much longer for the dead zones to wash out of the lake after this spillway opening, which is much more substantial than the one in 2008.

He says it not unreasonable to expect us to still have dead zones in the lake five years from now.

The worst part of all this is that it doesn’t have to be this way. If the Corps of Engineers would simply extend the eastern guide levee of the Bonnet Carre spillway to include all of the LaBranche wetlands, the river water would slow down, and dump most of its sediment and nutrient load into the marshes, where they’re needed, rather than in the lake.

Carlton Dufrechou argued this for years, but it apparently makes way too much sense to be implemented.

About Todd Masson 731 Articles
Todd Masson has covered outdoors in Louisiana for a quarter century, and is host of the Marsh Man Masson channel on YouTube.