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River Delta

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Tchefuncte River Delta

The Tchefuncte River (chuh-FUNK-tuh) drains into Lake Pontchartrain in Louisiana in the United States. The Tchefuncte River is named after a Native American Tribe that inhabited the area from 600 B.C. to A.D. 200. In 1811, a small town established on the banks of the river was named Madisonville, in honor of President James Madison It is about 48 miles (77 km) long. It rises in northeastern Tangipahoa Parish (N 30° 54.367 W 90° 20.983) and initially flows southward; the river is used to define part of the eastern boundary of Tangipahoa Parish and parts of the western boundaries of Washington and St. Tammany Parishes before turning southeastward into St. Tammany Parish, where it passes the city of Covington and the town of Madisonville. It collects its largest tributary, the Bogue Falaya, at Covington. The Bogue Falaya, also known as the Bogue Falaya River, is a river, about 23 miles (37 km) long, it meets the Tchefuncte River @ (N 30° 26.383 W 90° 06.983) and flows into Lake Pontchartrain about 2 miles (3.2 km) south of Madisonville,(3N 30° 22.600 W 90° 09.633) near the lake's northern extremity.

At the mouth of the Tchefuncte River, are the marshes area in St. Tammany Parish, an area considered one of the highest quality emergent coastal wetland sites in Louisiana. The marsh type is noted for relatively high plant species diversity with over 40 species according to LSU researchers. Sawgrass, a quality marsh indicator that is uncommon in southeast Louisiana, is prevalent throughout most of the site. The swamp is dominated by bald cypress, swamp red maple, swamp black gum, tupelo gum, and dwarf palmetto. Small pockets of open water are covered with white water lily in the swamp and marsh areas. The Tchefuncte River and associated coastal marsh and forested wetland communities provide habitat for many species of conservation concern, such as the federally-listed Gulf Sturgeon, and state-rare species including Bald Eagle, American Paddlefish and Osprey. These habitats are also important habitat for many migratory bird species, including numerous waterfowl, water birds and songbirds. The Tchefuncte River Marshes are extremely scenic, with expansive vistas present along the river, lakefront, and Lake Road (Louisiana Highway 1077). It is one of the few marshes on the Northshore accessible by a public road. Views from the Low- and High-Bridge canals and bridges are especially beautiful, allowing long-distance views of tall marsh grasses, moss-draped bald cypress and the historic lighthouse. From blooming Louisiana irises, swamp hibiscus, and morning glory to area wildlife such as alligators and wading birds, the site is classic coastal Louisiana. Sunsets are spectacular and during certain times of year, thousands of tree swallows and purple martins can be seen overhead, moving to and from their roost. Just since the Lighthouse was built near the mouth of the river, the area has endured over 175 years of erosion, the original terrain consisted mostly of native species of brush and trees that help anchor the receding coastline from the encroaching waves. But because of cypress logging, saltwater intrusion, evasive non-native flora and nutria predation, the hydrology of the area changed, preventing repopulation and leading to the death of several of the giant cypresses near the mouth of the river.

From this point in the delta you can see several of the rivers hazards. The Sand Bars, Shell Reefs and several sunken hazzard just below the serface. River Deltas are dangerous to ships coming to ports and this delta is no different. On the left side you will find no less than 3 sunken vessels that are still visible. In 1838, The Tchefuncte River Lighthouse was built to guide vessels thru the hazardous waters… Originally the lighthouse stood only 30 feet tall. This structure however was destroyed during the Civil War. It was rebuilt into what we see today.

WHAT IS A RIVER DELTA?

Deltas are the result of interacting fluvial (river) and, usually, marine systems. However, they can form anywhere a stream flows into shallower open water. Whence the name Delta? Delta was coined by Herodotus (the father of history, 484-425 BC) after the Greek letter delta because of the deltoid-shape at the mouth of the Nile.

Delta definition: Coastal accumulations, both sub aqueous and sub aerial, of river-derived sediments adjacent to, or in close proximity to, the source stream, including the deposits that have been secondarily molded by various marine agents, such as waves, currents, or tides. [L. D. Wright, 1978]

Deltas occur throughout the world, except at the poles. They all have three characteristics in common:

1. The presence of a large catchment, or drainage, basin (the area where all run-off water drains to the river). The top 30 river deltas all have catchment basins in excess of 1,000,000 sq km.

2. They all are at the mouth of large river systems that carry large quantities of clastic sediments (soils or portions of rocks that have been moved by water from where they formed).

3. They are not near geologically active coastlines. In order to have a large catchment basin, a very complex tributary system is necessary. These long, complex systems take a long time to develop, so they are very rarely situated on tectonically active coasts.

ANATOMY OF A DELTA:

I. Subaqueous (=under the water) delta - That part of the delta that is below the low-tide mark. Seaward, finer and finer soil particles are found. The seaward-most portion has the finest soils (clays) and is called the prodelta.

II. Subaerial (=under the air, or, above water) delta – That part above the low-tide mark.

A. Lower delta plain - That part governed by riverine / marine interaction. Extends land ward to the limit of tidal influence. All salt and brackish flora and fauna are within this area.

B. Upper delta plain - That part governed by riverine depositional processes.

On the same figure, one can see the following two additional categories:

1. Active delta - That part that is still active and has water channeling through it carrying sediment.

2. Abandoned (or inactive) delta - That part that was once active, but now has reduced or no fluvial activity.

TYPES OF DELTAS:

1. Arcuate (fan-shaped) delta - e.g., Nile River. Has many active, short distributaries taking sediment to their mouths. The receiving (ambient) waters are rather shallow and have relatively even wave action arriving perpendicular to the shore with minimal long shore current. As the sediment exits the many dis-tributary mouths, the waves push it back, so the coastline is rather smooth.

2. Bird-foot (shaped like a bird foot) delta - e.g., Mississippi River. Tend to have one or a very few major distributaries near their mouths. The receiving basin has currents that carry the sediment away as it exits the distributary mouth. There is a broad, shallow shelf that deepens abruptly, so the trend is to grow long and thin like a bird's toe.

3. Cuspate (tooth-shaped) delta - e.g., Tiber River of Italy. Usually has one distributary emptying into a flat coastline with wave action hitting it head-on. This tends to push the sediment back on both sides of the mouth, with a "tooth" growing out onto the shelf.

4. Estuarine delta - e.g., Seine River of France. This type of delta has a river that empties into a long, narrow estuary that eventually becomes filled with sediment (inside the coastline).

DELTA TERMS:

Progradation - The river deposits sediments faster than the sea is able to remove them, so the delta grows outward into the sea (=progrades).

Aggradation - The river deposits build up (elevation) via overbank flooding, accumulation of biotic remains, etc., so the delta grows upward.

Transgression - The retreat of the delta, usually by the loss of sediment caused by continued wave attack or the reduction of nourishment soils.

It follows that deltas have four options:

1. They stagnate, i.e., remain in equilibrium.

2. They prograde.

3. They aggrade.

4. They transgress.

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Your filing requirements are...

1. Take a picture of yourself with your GPSr and post it at the time of the log.You may want to have the distant lighthouse or one of the sunken vessels as your background.

Email me the answers to questions 2, 3 & 4.

2. From your vantage point Near Ground Zero, What is the largest hazzard ou see?

3. How long do you estimate the closest Sand Bar to be?

4. What type of delta is this one?

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More interesting information about this area...

Tchefuncte River Lighthouse N 30° 22.781 W 90° 10.147

Built in 1838, The Tchefuncte River Lighthouse is a monument to Southeast Louisiana's nautical history. Located at the mouth of the Tchefuncte River and just south of the town of Madisonville, Louisiana, this lighthouse has stood the test of many fierce Lake Ponchartrain Storms. Standing over 43 feet tall and made of brick and stucco, this is one of the oldest structures along the lake. Originally the lighthouse stood only 30 feet tall. This structure however was destroyed during the Civil War. It was rebuilt into what we see today. Although only currently accessible by boat and in grave disrepair, plans are currently underway to restore the lighthouse to its once grand stature. If restoration efforts work the light keeper's quarters, which are now located at the Madisonville Boatyard, are hoped to be once again placed next to the lighthouse.

Tchefuncte River Lighthouse has provided a beacon for boaters on Lake Pontchartrain for 175 years. Now the destruction that ships' cannons only could do temporarily, coastal erosion threatens to do permanently.

Places to go and things to do, St Tammany is beautiful place to see, and We Want To See You!