Ecology of the Mississippi River Delta Region
THE MISSISSIPPI RIVER
This is the mighty force that has formed the largest delta in North America. The Mississippi drains 41% (1.25 million sq mi) of the continental U.S., including 31 states and two Canadian provinces. It is 1200 mi by river from Cairo, IL, to the mouth of the river, and only 600 mi as the crow flies; also, it is 569 mi from the Arkansas/Louisiana line to the Gulf by river, but only half that in a straight line distance. Over this 569 mi length, its elevation drops 115 ft, or 2.5 in/mi. Rufus LeBlanc, an early expert on the geology of coastal Louisiana, said “No pool table is that flat.”
A few years ago, I was visiting the Jamestown Nature Center in the snow belt country of eastern New York. The grounds were covered with 30 in of snow and the ponds were all thickly iced over. As we stood in the cold, far from New Orleans, we watched a trickle of water flow from below the ice, over a weir, and back under the ice of an adjacent creek. Jim Yaich, the nature center director, said, "This water runs from our ponds, down this stream into Conewango Creek, then into the Allegany River, on to the Ohio River, and finally into the mighty Mississippi." This struck home: Here I stood in 30 in of snow watching water molecules flow from beneath ice that were potentially destined to be my drinking water at home! The Mississippi truly has a vast drainage basin.
There are presently no major tributaries in Louisiana, but the Red River was connected to the Mississippi River at one time. The only current distributary is the Atchafalaya River (other than the short channels near the river's mouth: Southwest Pass [where all commercial shipping travels], South Pass [lots of crew boats and big time sports fisherpeople fishing out of Port Eads], and Pass a Loutre [small vessels and some barges]). There were many channels that during historic times functioned only during high water periods when they would become navigable. The last three that were separated from the river, and their last date of connection, are as follows:
- Bayou Plaquemines - 1770
- Bayou Manchac - 1826
- Bayou LaFourche - 1902