Out of the Gulf, Part I

Nature has taken many years to delicately handcraft the perfect Sportsman’s Paradise.

Louisiana sportsmen are truly blessed with a variety of landforms that God seemed to have made specifically for the myriad fish and animals we enjoy pursuing. Whether chasing speckled trout in the southern marshes or popping fox squirrels in the piney hills, Louisianians have easy access to swamps, rivers, lakes and woods that provide endless opportunities for the outdoorsman.

How this great state’s landforms were created is a unique and fascinating story. It is also a story that continues to unfold with new twists and turns. Geological forces and human activities are constantly changing the landscape, and it is debatable whether the Louisiana our great-great grandchildren will enjoy will be the same as we see today.

Gulf Coastal Plain

Louisiana is a unique state, not only in its history, culture, food and music, but also in its geology and geography. Among other things, Louisiana is the nation’s wettest state, with 3,593 square miles of water. Swamps and coastal marshes cover much more. In all, 25 percent of the state is wet in some fashion, and nearly 40 percent of the nation’s coastal wetlands are found here.

Being so wet, it is appropriate that Louisiana literally rose out of the sea. When North America was formed millions of years ago, modern-day Louisiana was actually the sea bed of the ancient Gulf of Mexico. Today in North Louisiana, it is common to find sandstones with sea shell fossils, and shark teeth can be found where the old sea bed is actually exposed in such places as Copenhagen in Caldwell Parish.

During this ancient time, the mouth of the Mississippi River was located in present-day Arkansas. As the river deposited its sediments into the Gulf of Mexico, a coastal plain was slowly built up. This Gulf Coastal Plain extends across much of the Gulf Coast, but Louisiana is the only state that lies entirely within it.

For hundreds of thousands of years, the world’s climate switched back and forth between ice ages and warm interglacial periods. During the ice ages, the ocean levels dropped as much as 400 feet because most of the world’s water became trapped in glaciers, and no longer flowed into the sea.

During those times, Louisiana’s coastline extended far out into the Gulf to the continental shelf, and the Mississippi River spewed its sediment onto the deep ocean floor. Today, when offshore fishermen snag red snapper on the bottom 50 feet or more beneath their boat, they are actually fishing over what used to be dry land.

During the warm interglacial periods, ice melted, ocean levels rose and the Louisiana coastline retreated. Approximately 125,000 years ago, the Louisiana Gulf coast was just north of Lake Charles!

During these warm periods, Mississippi River sediments settled along the shallow coastline and built up the Gulf Coastal Plain. This process repeated itself many times until about 10,000 years ago, when the last ice age ended and the Gulf stabilized at about its current level.

Today, the Gulf of Mexico is the fifth largest sea in the world. It covers 582,100 square miles and has an average depth of 5,297 feet (about one mile).

Because of its irregular shape, Louisiana has more than 1,000 miles of coastline, the sixth-longest coastline of any state.

Power of rivers

When the last ice age ended, glacial runoff and higher levels of rainfall greatly increased the size of the Mississippi River and other Louisiana streams. These rivers largely shaped the Louisiana we know today.

• Meanders. Most of our rivers are meandering streams that wander through a flat valley called a floodplain. Because water always seeks the path of least resistance, Louisiana’s rivers meander back and forth in large loops and curves, much like a snake crawling across the floodplain.

These meanders are caused by obstacles in the water’s path. When a river flows in a straight line, it eventually will encounter a hill or hard soil on one river bank or the other. This obstacle forces the current to ricochet to the opposite river bank and begin eroding that bank away. Once a small curve is made, the water is directed back across the stream to erode away the other bank, and the process continues until a long series of meanders is created.

• Point Bar. The soil that is eroded out of the river bank is carried downstream as sediments, and is deposited on the river bottom, where the current slackens along the inside of the next meander. This creates a point bar that will continually build out into the river, forcing the current to erode away more of the opposite bank. Over time, the meander becomes larger and larger until it nearly creates a circle around a narrow neck of land.

Today, old point bars often appear to be long, slightly curved ridges that run parallel to one another. In some places, the river that formed them has shifted miles away, leaving the old point bars as ridges in the low-lying back swamp. Such ridges are excellent places to hunt deer when high water floods the surrounding lower area.

After creating a series of meanders, the river expends a great deal of energy to advance a short distance. Always seeking the path of least resistance, the river will eventually straighten itself by cutting across one of the narrow necks of land. When this happens, the ends of the old meander will close up to form an oxbow lake, and the narrow neck of land becomes an island.

In modern times, the Corps of Engineers has also created islands and oxbow lakes by intentionally straightening the river at meanders. Legendary deer-hunting islands Davis Island and Giles Island are two that were created when the Mississippi River cut off a meander.

The constant shifting of the Mississippi River has sometimes created problems in determining the boundary between Louisiana and Mississippi. Frequently, when the river has changed course, parts of Mississippi were left on the Louisiana side of the river and vice versa. This has caused several legal disputes between the two states over who owns what land. In 1995, the U.S. Supreme Court gave Mississippi ownership of Stack Island, near Lake Providence, and Louisiana lost 2,000 acres.

Many other Louisiana rivers have also changed course over the last few thousand years. The Red River, in particular, has shifted back and forth across its floodplain leaving old river channels that became smaller streams. Bayous Dorcheat, Boeuf and Rapides are actually old Red River channels.

When Natchitoches was established in 1714, it was located on the main branch of the Red River, but the river straightened out near Grand Ecore in 1834, and began flowing down a secondary channel that now is the actual river. In the 20th century, the abandoned channel at Natchitoches was dammed up and renamed Cane River Lake.

• Natural Levees and Terraces. Experienced Louisiana hunters know that even during floods there usually is a strip of dry ground that runs right along a river’s bank. Known as natural levees, these are excellent places to hunt deer during times of high water.

Natural levees are built up during floods when the river overflows its bank and spills onto the floodplain. In doing so, it immediately begins to lose current, and most of the sediments are deposited right along the river bank where the current first slows down. As the natural levee builds up higher and higher from these sediments, it slopes downward away from the river into the floodplain.

The building process for natural levees actually elevates the entire river bed, and the river bed will eventually become higher than the floodplain around it. Once this happens, the lower floodplain becomes the path of least resistance, and the river often will break through the natural levee during a flood and carve out a new channel.

After the river creates a new channel, the low-lying floodplain erodes even farther over thousands of years, and the old river bed becomes an elevated ridge called a terrace. Most terraces are 50-100 feet higher than the surrounding floodplain.

The Macon (MAY-son) Ridge in Northeast Louisiana is a good example of a terrace. Running north to south, it is about 100 miles long and 20 miles wide. Highland Road, on the main Louisiana State University campus, runs along another terrace, and gets its name from being higher in elevation than the surrounding area.

Any hunter who has ever struggled up and down the hills and gullies of West Feliciana Parish has experienced crawling over a terrace. Back during the last ice age, the West Feliciana terrace was covered with very small, wind-blown material called loess. After building up a thick layer on the terrace, the loess began eroding away, leaving the region scarred with deep gullies and bluffs.

Coastal marshes

Louisiana contains the nation’s largest marshland area, and all of it was formed by rivers flowing into the Gulf of Mexico. These wet grasslands teem with ducks, geese, fish, shrimp and crabs, and are heavily exploited by Louisiana sportsmen.

How important are Louisiana’s coastal marshes? Louisiana is the nation’s leading producer of seafood. Almost one-third of all the fisheries produced in the United States come from Louisiana wetlands. It is estimated that 95 percent of all marine life in the Gulf of Mexico spend part of its existence in the Louisiana coastal area, and 15 percent of the nation’s waterfowl winter in Louisiana’s marshes.

Additionally, approximately 80 percent of all the oil and natural gas produced in the United States travels through our marsh on its way to the consumer.

• Deltas. When a river flows into the Gulf, sediments are pushed out onto the shallow ocean floor in a fan-shaped pattern. Rather quickly, these sediments build up new land called a delta.

At the very mouth of the river, the sediments also create a bar, or underwater mud barrier, that partially blocks the river’s current. Following the path of least resistance, the river will split to go around the bar, and eventually those two new channels will form their own bars and split again. As the process continues, the delta takes on the shape of a bird’s foot and creeps slowly out into the Gulf.

Mud lumps are one odd type of formation that fishermen may encounter in the Mississippi River delta. As heavy sediments are deposited onto the river bottom, the increasing weight builds up tremendous pressure that squeezes the finer, lighter sediments upward until they sometimes explode out of the river in a geyser of mud and water. Mud Lumps can be up to 12 feet high and cover 20 acres. They sprout up, remain for years and then erode away, only to be replaced by new ones.

• Marshes. When a river flows into the Gulf of Mexico, it continues to build a natural levee as its delta is pushed farther out into the sea. During floods, the river overflows the natural levee and deposits sediments in the shallow water alongside it. Soon, this part of the Gulf is filled in with sediments, and marsh grasses begin to grow. Depending on their nearness to the Gulf, coastal marshes can be freshwater, saltwater or brackish.

The Mississippi River formed most of Louisiana’s coastal marshes. For thousands of years, it frequently changed course as it searched for the path of least resistance to the Gulf. The modern-day streams of Black River, Bayou Maringouin, Bayou Cypremort, Bayou Teche, Bayou Lafourche and the Atchafalaya River actually are old Mississippi River channels.

The last shifting of the Mississippi River occurred about a thousand years ago when it moved from what is now Bayou Lafourche to the present-day channel in Plaquemines Parish. In fact, a thousand years ago, Plaquemines Parish did not even exist. The entire parish was created by the Mississippi continually pushing its delta farther into the Gulf.

• Cheniers. Cheniers are very popular places to hunt deer and rabbits in the marsh. Made of shell and sand, these ridges run parallel to the coastline, and are usually 4 or 5 feet high and sometimes several hundred yards wide. Pecan Island and Holly Beach are examples of large cheniers.

Cheniers are old beaches that were created and then abandoned as the Gulf’s water rose and fell over thousands of years. The French called the ridges “cheniers” (place of oaks) because numerous live oak trees were found on them.

Cheniers have always been important places for both man and beast because they provide people and animals a dry place to live in the marshes. They also help protect the coastal marshes from hurricane storm surges and saltwater intrusion.

• Barrier Islands. Barrier islands are quite common along the Louisiana Gulf coast, and they provide some of our best saltwater fishing. These islands are created after a river changes its course and abandons a delta. Without fresh sediments to maintain it, the delta erodes away until only the sturdy bar that formed at the river’s mouth remains. Eventually, all the marsh that built up along the river channel is washed away, leaving open water between the mainland and the old bar.

Waves and tides gradually deposit sand onto the bar until it finally emerges from the Gulf as a string of crescent-shaped islands. The Chandeleur Islands are the remnants of the Mississippi River bar that was created when it flowed through St. Bernard Parish. The Timbalier and East Timbalier Islands, Isle Derniere, Grand Isle and Grand Terre are the old delta bars that formed when the Mississippi flowed down modern-day Bayou Lafourche.

Grand Isle is one of the state’s most popular barrier islands for sportsmen. What most beachcombers and fishermen do not realize, however, is that Grand Isle actually is moving from west to east about 16 feet per year. Waves and Gulf currents cause the island’s western end to erode away, while the eastern end is built up by the shifting sand. About 150 years ago, today’s Grand Isle State Park was open Gulf water.

In addition to the fantastic fishing they provide, barrier islands protect the mainland from erosion by absorbing storm surges. They also help regulate the salinity of the marsh water by blocking salt water from entering the marsh during storms. Without the barrier islands, coastal erosion would greatly accelerate.

Coastal erosion

One of the greatest threats facing Louisiana today is coastal erosion. Louisiana has 40 percent of the nation’s coastal wetlands, yet it suffers 80 percent of the wetland loss. The state literally is shrinking as the marshes wash away into the Gulf.

Louisiana is losing approximately 35 square miles of land a year, or an area the size of Rhode Island in the last 50 years. Every hour, about 2.5 acres, or an area the size of two football fields, disappears. In many places, where cows grazed on pastures a few years ago, there now is only water.

Some of this erosion is a natural process. As millions of tons of sediments are deposited onto a river delta, the sheer weight causes the entire area to sink. As long as the river deposits sediments, however, the marsh builds up faster than it sinks. If the river changes course and abandons the delta, the marsh continues to sink, but no new sediments are being deposited, and the process reverses. Ocean waves and hurricanes accelerate the erosion until the marsh finally disappears beneath the Gulf.

Despite these naturally destructive forces, Louisiana’s coastal marshes remained healthy and stable until the 20th century. Even though some of the marsh was destroyed in one area, river sediments built up new marshland somewhere else.

About a hundred years ago, human activity began interfering with this natural process. Extensive levee systems were constructed along rivers for flood control, and these levees keep the rivers’ water confined inside their channels. As a result, the rivers now shoot the sediments straight into the Gulf’s deep water, and they can no longer overflow their natural levees to deposit fresh sediments in the coastal marsh.

Another problem is that reservoirs constructed on rivers trap sediments and prevent them from reaching the marsh. In fact, only about half the amount of sediments reach the Gulf today as did a hundred years ago.

The oil and gas industries have also accelerated coastal erosion by constructing numerous canals and pipelines through the marshes. These often allow salt water to intrude from the Gulf of Mexico and kill the marsh grasses that hold the soil in place.

In addition, so much oil has been removed from beneath the marsh that a void has been created deep underground. The Earth’s crust can no longer hold up the weight of the marsh, and it steadily sinks.

Some steps are being taken to stop coastal erosion. Grasses are being planted in some areas to help hold the soil in place, and sand is being pumped onto barrier islands to keep them from eroding away. Also, the U.S. Army Corps of Engineers has completed several projects that allow sediment-rich Mississippi water to flow into the marsh to stabilize it and even rebuild some lost areas.

The Caernarvon Diversion Project was completed in 1991 at a cost of $26 million. Located 15 miles downstream from New Orleans, it allows Mississippi River water to flow through the levees into coastal marshes.

Twenty-three miles upstream from New Orleans is the Davis Pond Freshwater Diversion. Completed in 2002 at a cost of $120 million, it allows Mississippi River water to flow into Barataria Bay’s marsh.

Recently, the Corps of Engineers also decided to close the Mississippi River Gulf Outlet (MRGO). Completed in 1965 to provide merchant ships a shortcut from the Gulf to New Orleans, the MRGO has devastated much of St. Bernard Parish’s marsh. The 76-mile-long canal cut through four natural levees and allowed salt water to intrude into the marsh and kill the grasses. Erosion has been so steady the original 650-foot-wide canal is now 2,000 feet wide in some places.

Part II of “Out of the Gulf: The Making of the Sportsman’s Paradise” will appear next month. Terry L. Jones is a professor of history at the University of Louisiana at Monroe. This article is based on his Louisiana history textbook The Louisiana Journey (Gibbs Smith Publishers, 2007).

About Terry L. Jones 114 Articles
A native of Winn Parish, Terry L. Jones has enjoyed hunting and fishing North Louisiana’s woods and water for 50 years. He lives in West Monroe with his wife, Carol.