Mississippi Flooding May Have Little Effect on Delta Wetlands

Much of the southern and southeastern part of the state of Louisiana is delta. There are two, the larger Mississippi River delta and the Atchafalaya River delta, separated by wetlands of all description. For hundreds of miles, the coast of the Gulf of Mexico is an ever changing mix of marsh, mud flat, channels and swamp.

As the record flooding of the Mississippi River flows southward, both deltas are increasingly receiving this massive volume of freshwater and sediment. Will this event have any effect on the plants and animals that live in this unique ecology? We spoke with Cassidy LeJeune and Todd Baker, biologists with the Louisiana Fish and Wildlife Service, about the potential effects that the Mississippi Flood of 2011 might have on the two deltas.

How high will the water rise? Both scientists told us that it was unlikely that the rise in water level in the deltas would be greater than 12-24 inches. The deltas are a maze of waterways that distribute the waters of the two rivers so widely that a major increase in water level is unlikely. Delta water levels are primarily affected by ocean tides and the wind.

The drought that most of Louisiana has been undergoing in the past year or more is also not an issue in the deltas. The way the rivers flow into the deltas means that only a very severe drought might have an effect. Some of the higher spots might show some drought damage, but the overall area has not.

LeJeune described the flood of 2011 as a "monumental event" and said that the scientists are "curious to see what the end result may be." One result may be the creation of new land through the deposit of sediment. Channels may become shallower or mud flats created. In some areas, the addition of sediment may lead to the recruitment of vegetation, bringing marsh plants to areas that do not have them at this time.

It is alligator nesting season in the two deltas. Routine monitoring conducted later this summer should determine if the rising water had any effect. Alligators nest on dry land and some nests could be drowned by the higher water.

Rising water, even the small increase foreseen by Baker and LeJeune, may force land animals to higher ground. It could result in an abnormal mix of predator and prey in a confined space.

The two also expressed concern about the movement of feral pigs due to the changes in water level. Feral pigs are the result of the release or escape of both domestic pigs and European boar in the past. Feral hogs are omnivorous, eating both plants and animals. They can be aggressive, including toward humans, and those of European descent have tusks.

Louisiana maintains two delta wildlife management areas (WMAs). Both are sited well out in the marsh and accessible only by boat. Fish & Wildlife Service employees live on site and monitor conditions in the two WMAs daily. The Atchafalaya Delta WMA covers 137,000 acres and the Pass A Loutre WMA covers 115,000 acres. Both locations allow state scientists to observe the ecology of the deltas and any changes that may occur.