Physical features along Mississippi River

Tributaries
The Mississippi is joined by the Minnesota River south of the Twin Cities, the St. Croix River near Prescott, Wisconsin, the Wisconsin River in Prairie du Chien, Wisconsin, the Rock River in the Quad Cities, the Iowa River near Wapello, Iowa, the Skunk River south of Burlington, Iowa, the Des Moines River in Keokuk, Iowa, the Illinois River and the Missouri River near St. Louis, and by the Ohio River at Cairo, Illinois.

Waterfall

Formation

1) By flowing across zones of rock with different resistance to erosion
§ River flows across near vertical bands of rocks of different degrees of resistance to erosion
§ Less resistance rocks erode faster resulting in abrupt steepness in gradient
§ Waterfall forms where there is sudden fall in height
§ River plunges and hits the bottom of the river bed with great force
§ Rocks swirl around base forming deep pool known as plunge pool

2) By faulting
§ Rocks are uplifted
§ Displacement of rocks results
§ One layer of rocks higher than the other
§ Gradient of the river bed changes abruptly

River Warren Falls
It was North America’s greatest waterfall. River Warren Falls formed in what is now downtown Saint Paul, Minnesota, at the end of the last Ice Age. The power of the cascading waters continually eroded the base of River Warren Falls and over the next several thousand years the waterfall moved 15 miles up the Mississippi River creating a deep gorge. It ended up in downtown Minneapolis as Saint Anthony Falls—the “Waterfall that Built a City.” In its wake, a rock-walled gorge was carved. Streams became waterfalls as they leapt into the chasm, and none more famous than the Minnehaha Falls celebrated in the epic poem, The Song of Hiawatha, by Henry Wadsworth Longfellow.

The only waterfalls along the entire 2,300-mile length of the Mississippi River. It is a thoroughly researched book that chronicles the early explorations of the Upper Mississippi River, leads you to tropical marine corals captured in stone, reminisces on the visits of Henry David Thoreau, Mark Twain, and Dvorak, and tells the tale of a 200-pound rodent dropped dead in the prime of its life.

Meanders

Characteristics
- Twists and turns or hoop-like bends in river
- Most prominent in middle and lower courses but can occur anywhere along course
- No depositional landform formed on concave bank because water too swift with little or no load.

Formation

§ Upper Course:
- Gradient steep but meanders occur when river volume and energy low; due to obstacles e.g. resistant rock outcrops, hence twist and turn to avoid obstacles to find easiest route.

§ Middle Course:
- gradient gentler
- flow velocity and energy decrease
- insufficient energy for vertical erosion despite greater volume as gentler gradient means weaker gravitational pull
- Lateral erosion dominant
- Lateral erosion dominant
- Lateral cutting or erosion causes meanders to form
- Speed of flow faster and stronger on concave bank causing erosion by undercutting
- Speed of flow slower on concave bank causing deposition

§ Most common in lower course of river
§ As erosion and deposition continue on concave and convex banks respectively, meander becomes more pronounced and separated by narrow neck

As it winds from Minnesota to the Gulf of Mexico, the Mississippi River is in constant flux. Fast water carries sediment while slow water deposits it. Soft riverbanks are continuously eroded. Floods occasionally spread across the wide, shallow valley that flanks the river, and new channels are left behind when the water recedes.

Levees
Natural embankment formed by coarser alluvium deposited on and along river banks

Formation
- As floodwaters subside, coarser materials get caught on banks and settle on them
- Accumulation of coarser materials on banks raises them higher than floodplain to form levees
- Abundant sediments brought down by rivers may cause river beds to be raised
- River channel will thus flow at an elevation higher than floodplain

The Mississippi River levees are designed to protect the alluvial valley against the project flood by confining flow to the leveed channel, except where it enters the natural blackwater areas or is diverted purposely into the floodway areas.

The main stem levee system, comprised of levees, floodwalls, and various control structures, is 2,203 miles long. Some 1,607 miles lie along the Mississippi River itself and 596 miles lie along the south banks of the Arkansas and Red rivers and in the Atchafalaya Basin.

The levees are constructed by the federal government and are maintained by local interests, except for government assistance as necessary during major floods. Periodic inspections of maintenance are made by personnel from the U.S. Army Corps of Engineers and from local levee and drainage districts as it is essential that the levees be maintained in good condition for their proper functioning in the flood control plan.

Delta
Flat piece of land made up of layers of sediment deposited at river mouth over time.

Characteristics
- Triangular-shaped flat alluvial plain at river mouth marked by numerous disbutaries
- Delta classified according to shape
- Most common shape is triangular
- Composed of fertile alluvial soil vital for agriculture

Formation
- When river enters water body, river velocity and energy decrease causing deposition to occur
- Sand deposited close to shore, while fine slit and clay carried further out to sea before being deposited
- Over time, layers of sediment build up and form extensive platform of sediment at river mouth
- Triangular-shaped depositional feature is delta
- Smaller delta may form in same way when river enters lake

The Mississippi River Delta is the modern area of land built up by alluvium deposited by the Mississippi River as it slows down and enters the Gulf of Mexico. The deltaic process has, over the past 5,000 years, caused the coastline of south Louisiana to advance gulfward from 15 to 50 miles (24 to 80 km).

It is a biologically significant region, comprising 3 million acres (12,000 km²) of coastal wetlands and 40% of the salt marsh in the contiguous United States. It is also a commercially significant region, supporting the economy of New Orleans with significant shipping traffic, providing 16 to 18 % of the US oil supply, and providing 16 % of the US's fisheries harvest, including shrimp, crabs, and crayfish.

The Mississippi River Delta is not to be confused with the Mississippi Delta region, an alluvial plain located some 300 miles northward in western Mississippi along the River.

Oxbow lake
Truncated section of meander in river channel which form ‘c’ shape

Formation
- Erosion takes place on concave bank and deposition on convex bank of meander
- As erosion and deposition continue on concave and convex banks respectively, meander becomes more pronounced and separated by narrow neck
- Overtime, river breaks through narrow neck and flows through straight channel. Deposition begins to cut meander off from river
- Eventually, meander completely cut off and oxbow lake forms

The Reelfoot Lake in west Tennessee is an oxbow lake formed when the Mississippi River changed course following the New Madrid Earthquake of 1811–1812. There are many oxbow lakes alongside the Mississippi River and its tributaries. The largest oxbow lake in North America, Lake Chicot, was originally part of the Mississippi River.