More than a Spillway…

This is the beginning of a discussion about the Basin and its future. Please feel free to comment if you like.
These thoughts are mine and may not reflect those of the FOA Board or membership.

After watching and participating in Basin activities for more than a decade now, i have started to realize some basic concepts that are occasionally mentioned but which most folks apparently don’t appreciate as significant.

We steadfastly charge forward to improve the hydrology of the Atchafalaya Basin, trying to improve the water quality in vast areas of isolated swamps, but we seem to ignore why the swamps are isolated and what it will take to fix them.

It wasn’t always like this.

Back before any levees were built by humans, nature built her own, but they were low ones, gradually built by depositing layer after layer of sediment just behind the higher banks of the rivers and streams. Water, over-topping the natural levees, tended to spread out and slow down, so it dropped the larger grains behind the existing levees and extended them away from the channel. The higher the water level, the greater the amount of sediment that was laid down. Eventually, the higher ground tended to resist the over-topping and water broke through weaker spots in the banks to change the route of the channel. This process went on for thousands of years, building the Mississippi/Atchafalaya delta and many others around the world. Overlaid on this process was the rise and fall of sea level as the earth warmed and cooled for various reasons.

As migrating Europeans started to build communities along the rivers, pressure became stronger to minimize the disruption of the periodic floods caused by the rise of the channels draining a large part of the continent and higher levees were built, until the Mississippi was converted into one long, mostly-constrained, channel draining much of North America into the Gulf of Mexico. Occasionally, though, the levees could not contain the huge drainage flow and the resulting floods were higher than earlier ones because the channel was kept artificially high inside its new channel, rather than being allowed to spread across a wider area.

None of this is new to most of us, nor is the process than led to the creation of the Atchafalaya, West Atchafalaya and Morganza Floodways, the creation and expansion of the Old River Control Structures, or the modifications of the main channel of the Atchafalaya River into a deep, wide, fast moving, efficient carrier of water to the Gulf. In telling the story, we often mention that the Corps of Engineers was directed to place a high priority on flood control and transportation, ultimately to the detriment of the swampy areas. We also discuss the construction of logging and petroleum access canals across the Basin and point out that many of them contributed to the blockage of natural north-to-south flow of water in the swamp. Then we start talking about what small changes we can make to some of the blockages in order to restore health to the swamp.

What we don’t talk about is the fact that the biggest impact to water flowing in the swamp is not the blockages of small channels, it is the opening of the largest one. And we don’t point out that the biggest causes of the problems in the swamps are still recognized as the highest priorities of the Corps of Engineers, the organization that is charged with the responsibility of managing the Atchafalaya Basin Floodway System. Let this soak in: the Atchafalaya Basin Floodway System is, 1) first and foremost, a conduit for water from the Mississippi River to the Gulf of Mexico; and 2) a path for the transport of goods and services between southern and northern ports. The fact that the “Basin” is available as a quasi-natural habitat for plants and animals and a recreational area for people, is a result of the decision to maintain the area undeveloped so that its flood carrying capacity is not diminished by obstructions or by economic pressures not to flood industry or communities in the area.

Whether you agree with the priorities in place, or not, it is important to understand the effects of them on the health of the ecosystem.

It is my opinion that the restriction of water to the main channel[s], either actively, by closing off most outlets from the main path down the middle of the Floodway, or passively, by deepening and widening the largest channel so that the resistance to flow into the swamps is greater than the resistance to direct flow to the Gulf, is the biggest cause of poor water quality in the remaining swamps.

In order to improve the flow of water into the areas that need it for forest and wildlife health, we must first decide that the health of the ecosystem is at least on the priority scale with flood control and transportation, and then figure out how to manage the flow down the main channel during different water conditions to allow all three needs to be met more equitably.

In other words, we need to control the balance of the flow down the main channel and into the swamp, whenever flood control is not a big issue, so that we can conserve the resources that we have decided are important in the swamps.

In short, we need to make a conscious decision that the Atchafalaya Basin will not be just a Spillway.

The time for this discussion is way overdue, but the recent directive to the Corps to re-visit the management of the Old River Control Structure and to make recommendations for the distribution of flow between the Rivers make this a good time to lay it all on the table and to discuss the social value of the Flood Control function, the strategic and commercial values of the transportation activity on the Atchafalaya River, and the environmental and social values of the natural resources inside and adjacent to the levees.

Let’s talk.

Charles Caillouet,